African Processed Meats: West African Roots
9 April 2023
Eben van Tonder
Food is one of the most intimate cultural expressions, on par with religion. Methods of preparation and spices are pillars of the study of food and one of the oldest foods we consumed is meat. Europeans and Americans refer to one class of meat sausages as emulsion sausages. Examples include frankfurter-style sausages and mortadella luncheon meats. In South Africa russians, viennas and polony fall into this category. The origins of emulsion-style sausages are definitely not restricted to Europe. I traced the origins of this style of meats to antiquity when mortar and pestle grinding was used to create a meat paste and here in West Africa I encounter another example.
The two most important spices are salt and pepper. Salt fascinates me and I have a special section in the EarthwormExpress dedicated to its role in history, The Salt Bridge, celebrating its role in connecting societies and facilitating the transfer of culinary innovation since antiquity. In 2018 I did an article, Salt and the Ancient People of Southern Africa elucidating some of the important elements of the key role salt played in the lives of the ancient people of Southern Africa, particularly in relation to producing dried meat.
It is the link between dried meat, spices and grinding or pulverising meat that became a powerful telescope back into history when I had a fascinating meeting with three businessmen in Lagos, Hassan and his brother Hussaini Guruna and Saleh Buba, a business partner, friend and economist by training.
Meat was dried by hanging it in trees. Salt was indirectly used by rolling the strips of meat in ash before hanging it. The ash had the function of keeping the flies away but also added to the taste. William Ramwell sent me a comment earlier this year to my article on biltong I mentioned above, “I was working in the bush in Namibia in 1978 doing geological exploration. We were late and had to camp by the roadside. I had a team of 17 Ovambo tribesmen who proceeded to make a fire and slice up their meat into long, ragged strips which they then put on the wood fire. The ash-coated meat was absolutely delicious.” In a 2019 interview, I did with a guide at Echo Caves in the Mpumalanga region in South Africa whose memory through his father and grandfather goes back at least 170 years, told me that if the meat had a slight “off-taint”, they would roll it in the ash again before consuming it which would mask the unpleasant taste. I never forgot the statement which came back to me and was elucidated by William’s contribution that the ash indeed served a “spicing” role and positively contributed to the organoleptic characteristics of the product.
The dried meat was pulverised and used in soup dishes. The tradition is ancient and I found reports of ancient mortars and pestles, discovered in Southwest Asia dating back to approximately 35000 BC where it was applied to amongst other, meat. I examine this in The Origins of Polony.
The pulverised meat was often used with ground nuts. Elanor Muller, Marketing Manager at Transfrontier Parks and a student of culinary history provided me with the following detailed information regarding the practice of drying meat and then rehydrating it in a stew and its combination with ground nuts in Southern Africa. “The Zimbabwean Ndebele people have a traditional dish which they call Ewomileyo. Modern-day people add peanut butter to the dish. This is no doubt done in accordance with an old practice of adding nuts to the meat dish. It is also called Umhwabha or the Zulu name for it is Umqayiba. In Venda, it is done in two ways. Dried meat is placed on a braai or they grill it and stump it. It is then cooked, or dried meat is recooked and mixed with peanuts. All vegetables and meat, mixed with peanuts are called Dovhi.”
West Africa – Incubator of African Innovation and Technology
This week Hassan and his brother Hussaini Guruna and Saleh Buba visit us at our offices in Lagos. The first lesson they had for me related to descriptions of cattle. It is important for me to be able to make a clear distinction between cattle that are fat and healthy – ready for slaughter and gaunt, sick animals. Two Hausa words are used.
Gamba – the word used to describe gaunt cattle; and
Koshi – the word used to describe fat cattle (can also be referred to as Bujimi).
They then told me about the Yolo cattle market in Mubi. Cattle are driven in huge herds from Chad to the Northern Nigerian City of Mubi where cattle traders like the Guruna family, load them in trucks and transport them to Lagos where they are fattened and sold.
The discussion quickly turned to dried meat. In the Hausa tradition salt and spices are used to make the dried meat, but never sugar. The local variety known as biltong in South Africa and Jerky in America is called Kilishi. A bit of heat is sometimes employed to speed up the drying process.
Kilishi is, however not the only product made from dehydrated meat. One such progression of the basic concept is Dambu Nama.
To make this, all fat and connective tissue is removed from the meat after which it is rinsed and cooked with bell peppers, stock, onions and salt to taste. The meat is cooked till it is soft. All the water is cooked off and if need be, add more water and cook till dry. Traditionally, a mortar and pestle were used to grind the meat down but these days chefs prefer using two forks to shred the meat. The role of mortar and pestle is the key link for me. The tradition is ancient!
Suya spice, pepper, ginger powder and stock are added. Mix and taste to ensure the spices are to satisfaction. Now, fry on medium heat in a bit of oil, pressing down on the meat with your spachelor while stirring to ensure the meat remains fluffy. When the colour of the meat change to deep brown, it’s done and time to cool it down.
One of the other traditional ways that it is made is by adding groundnut cake. This piqued my interest as it connected to the Southern African inclusion of groundnuts into pulverised dried meat.
Groundnut cake is made as the byproduct of extracting oil from it, and yes, the process is also ancient and is still practised in households and small industries by Nigerian Northerners.
My mind goes back to the weeks and days I spend hiking the old indigenous ruins across the Johannesburg highveld area. I chronicled these experiences in The Stories of Salt. All we have left today are the ruins. Western colonisation destroyed the rich oral tradition of the indigenous tribes. It was always interesting to me that when I was amongst the ruins a calm came upon my mind and I knew that the truth about the rich history of these people would one day be told again. The height of their technology was in ways that Europeans did not perceive as valuable. For most of the inhabitants of the region (sadly, not all) technology was chiefly directed at communal living and not building vast empires. One of my projects is to rediscover this technology and particularly as it relates to meat and other foods.
It was with the greatest excitement that I learned the full details of the processing of dried meat and the way that groundnuts were added to meats. The ancestral spirit-guardians of the stone ruins of Southern Africa guided me to Nigeria and set an appointment with Hassan Guruna, Hussaini Guruna and Saleh Buba who would finally tell me what happened in the ancient mega-cities of Southern Africa, not by telling me what happened down South, but what is done here in West Africa where most of the ancestors of the oldest inhabitants of Southern Africa hail from.
Oil Extraction from Groundnuts
The groundnuts are first roasted. In the roasting process, the nuts are stirred repeatedly to prevent burning. After roasting it is removed from the fire and cooled down. The red coating is now removed either by hand or by lightly stirring it in a mortar and pestle. The red coating is removed by blowing it away. The remaining groundnuts, now without the coating is grind into a paste in the mortar and pestle.
The container for roasting is now returned to the fire and the paste is transferred to it. You can add water. Stir the paste. Add more water and keep stirring to avoid burning the paste. Stir it till the oil starts coming out. Bring it down from the fire and allow it to cool. The oil separates out. Wrap the paste in a cloth sieve and press the oil out with a heavy stone by placing the stone on top of the paste.
After collecting the oil, let it stand in a container to settle down and clear oil is now separated from solid bits that made their way through the sieve. What remains is the oil, used for frying and the groundnut cake which can be used in many different ways, for several dishes. One of the ways is in combination with shredded and pulverised meat that was either dried in the sun or dried over a slow fire or both.
The ancient method of extracting the oil is beautifully done by Sunshine Resources and I used their video and description above. Credit goes to them and their excellent video is posted below.
Saleh gave me another way that oil extraction can be done without the use of direct heat. Apply a small amount of boiled salt water to the paste and keep turning it without applying direct heat. A pure oil will start coming out. The process is, however, described as “stressful.” The role of salt is interesting and will require further investigation.
I will return from West Africa, armed with a truckload of specific sets of technology to investigate and find evidence that they were practised. West Africa has always been one of the areas in the world with the greatest technological advances. The existence of hundreds of languages and different writing styles, completely unique in their structure is a testament to this. It opens an avenue to discover technology that disappeared and was never recorded, filling in cultural and heritage gaps that exist in the rich indigenous culture of the South.
It contributed to my own quest to discover the specifics of the enormous meat culture of Africa. I am here to produce sausages and hams and various meat delicacies, but I am not interested in the European, English and American style of food only. My compatriots and I are fascinated to bring to the mass market, African delicacies and processed meats.
Finally, as a meat scientist, it solidifies my view that meat recipes with meat extenders (soy, starch, flour, etc.) are by no way inferior to pure meat recipes and that it is not somehow a modern invention. The tradition is ancient and the delicacies delicious!
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For several years now I have been looking into the use of the 5th quarter from animal slaughtering to find ways to use this more effectively in human nutrition. Despite legislative challenges which classify, for example, animal bones as inedible, thorough investigations have been carried out over the years which clearly show such legislation to be outdated and ill-informed. In other instances, it is due to mostly Western prejudice against the consumption of certain parts of the animal which made its way into legislation.
Some animal parts classified as in-edible in Western countries are customarily used in several non-Western countries as human food such as beef hides which is consumed in Nigeria as Ponmo (Kpomo). An attempt is being made in some Western countries to find a way past the outdated and ill-informed legislation by having such food classified as traditional dishes.
An even more surprising situation exists in a country like South Africa where it seems as if the authorities frown upon attempts to even investigate the use of these by-products in food processing. When they make their case, they do not refer to science, for example, to try and show that certain animal parts are harmful when consumed but to legislation in Western countries as if this is anything to go by. The unambiguous evidence of mounting research data is that consuming a great percentage of these so-called in-edible parts of a carcass is not dangerous to humans. On the contrary! It turns out to be highly nutritious and their inclusion in, for example, sausage formulations will add to the nutritional characteristics of the food and lower prices.
Over the last few years equipment has become available to process certain animal by-products in such a way that nutrition is enhanced by increased bioavailability, mostly through a greater degree of comminution. Disruptor technology has for example been pioneered in South Africa which reduce the particle size of these by-products dramatically. Ultrafine grinding of bones has become possible through a range of equipment and processes. The high-volume processing of such material will undoubtedly have to be done through equipment like the Dynamic Cellular Disruption (DCD) process, pioneered by Green Cell Technologies (GCT), but smaller machines for small processing are available.
This means that from the perspective of nutrition (backed up by thorough scientific research) and equipment, there is no longer any reason to maintain the archaic Western-focused aversion to the processing of the entire carcass and including most of it in food produced for human consumption should be legislated. In countries where bones and animal hides have not been classified as inedible, the status quo should remain unchanged for the benefit of the respective populations, culturally, nutritionally, and as far as affordability is concerned. From a philosophical perspective, it is my opinion that not utilising the full carcass for human nutrition shows great disrespect to the animal by somehow implying that certain parts are only good to feed other animals or fertiliser.
Animal Bones are Nutritious.
The first point that must be made about bones is that it is already part of human food in the form of broth and soups. If we just pause there and realise that in South Africa it’s classified as not fit for human consumption we can ask, so are we or are we not allowed to sell “meaty bones” (as is being done), as soup bones? So, the legislature allows it because this is an extremely popular South African product, despite being described, technically, as “not fit for human consumption.” So much so that the bones are no problem in South Africa and sell at such good prices that producers give bones not a second thought. The market exists for it by simply cutting it up with a bandsaw into smaller chunks.
Chicken bone is another example that is much softer than other animal bones and comes to us through MDM. In some countries in Africa, MDM is banned for no good technical reason and as far as Europe is concerned, it is a completely different reason which is beyond the scope of our current discussion.
Back to the South African example. We are allowed to sell all the bones in the entire country to be used in soups and we are allowed to use MDM which are packed with chicken bones, still using bone meal as is produced for animal feed around the world in food for human consumption will be a problem for the South African legislator.
These inconsistencies in handling the matter aside, the reality is that bones are packed with nutritional elements. The fat and protein content is, however, not parallel to that found in the rest of the body as some authors suggest. Paloheimo (1965) reported that the bone-free body of one of three Paloheimoof dairy cows analysed contained 25.2 % fat while the corresponding figure of the skeleton was 19.9. The second cow gave figures 15.5 and 22.0 respectively, and the third 14.7 and 19.0. They continued their study and analysed specific bones as opposed to the whole carcass bones as in the three dairy cows. The average percentage from the femurs of 20 cows and 4 young animals, where fat, protein and ash were directly determined and the water content was calculated as the difference, are as follows (ranges of variation given in brackets).
Fat 33.6 (26.9 – 38.9) Protein 17.2 (15.0 – 21.6) Ash 34.8 (33.0 – 33.9) Water 14.4 (11.3 – 16.0)
Bones serve amongst others, as a reservoir of calcium and phosphate ions for the entire body. It is “composed of various types of cells and collagenous extracellular organic matrix, which is predominantly type I collagen (85–95%) called osteoid that becomes mineralised by the deposition of calcium hydroxyapatite. The non-collagenous constituents are composed of proteins and proteoglycans, which are specific to bone and the dental hard connective tissues.” (Mohamed, 2008)
Yessimbekov (2021) investigated the use of meat-bone paste to develop calcium-enriched liver pâté. They found that “the compositional analysis of pâté manufactured with meat-bone paste showed that the reformulation did not influence the content of moisture (~56%), fat (~28%), or protein (~11%) while producing a significant increase of ash and a decrease of carbohydrates in comparison with control pâtés. The higher amounts of minerals of bone-meat paste, including calcium (3080 mg/100 g), magnesium (2120 mg/100 g), phosphorous (2564 mg/100 g), and iron (7.30 mg/100 g), explained the higher amount of both ash and these minerals in the reformulated samples compared to the control samples.”
The total caloric value (~300 kcal/100 g) was unaffected by the addition of bone-meat paste. “The content of both essential and non-essential amino acids decreased with the inclusion of meat-bone paste, although this decrease was lower in essential (6280 mg/100 g in control vs. 5756 mg/100 g in samples with 25% of meat-bone paste) than in non-essential amino acids (6080 mg/100 g in control vs. 3590 mg/100 g in samples with 25% of meat-bone paste). This fact is due to several essential amino acids not showing differences between control and reformulated samples, while in non-essential amino acids, these differences were greater.” (Yessimbekov, 2021)
“The results of this study showed that meat-bone paste addition is a good strategy to produce liver pâté enriched in minerals and with minimum influence on the content of the other important nutrients. Therefore, these results can be used for the design of new liver pâté with an increased nutritional significance by using meat industry by-products. According to the balance of minerals, the use of 15% of meat-bone paste to reformulate liver pâté is the best strategy used in the present research.” They caution that “additional studies on the stability (during storage), shelf-life, and sensory acceptability of these reformulated pâtés should be carried out.” (Yessimbekov, 2021)
Kakimov (2017) states that “bones are rich in mineral elements (in particular, calcium, phosphorus, magnesium and iron), protein (collagen) and fatty substances. Bone consists of 13.8 – 44.4% water, 32 – 32.8% protein (collagen), 28.0 – 53.0% mineral elements and 1.3 – 26.9% fat. The most characteristic components of bone are mineral elements, represented by calcium carbonate and phosphoric acid, followed by various oxides (%) (CaO 52, MgO 1.2, P2O5 40.3, Na2O 1.1, K2O 0.2, Cl 0.1, F 0.1 and CO2 5.0). Cattle bones, which contain between 9 and 14 mg kg–1 calcium are a major source for calcium and phosphorous salts.” They quote Drake et al., that “bone is a useful calcium source for nutrition because bone particles are readily dissolved by gastric juices. Moreover, the use of mineral salts in the production of meat-based products enables enrichment of food with mineral supplements, particularly calcium, phosphorous, magnesium and other elements that can be helpful in preventing diseases associated with mineral deficiencies, such as osteoporosis”. (Kakimov, 2017)
They state that “meat-bone meal can provide a rich source of whole protein and is an especially rich source of the essential amino acid lysine, as well as mineral supplements. For human consumption, bone is typically used to prepare protein hydrolysates and mineral supplements, bone broth and bone fat.” (Kakimov, 2017)
Kakamov (2017) describes a superfine bone grinding processes beginning with “crushing the bone to 1-3 mm particles followed by ultra fine grinding to yield 50-100 mm particles can be used to make paste-like products that have a soft texture and are fully digestible by humans.” He notes that such pastes can be used for the production of food supplements and different meat products such as sausages, pates and semi-finished meat products. Moreover, since the meat-bone grinding process does not involve thermal treatments, the vitamin, mineral and protein content is preserved
Kakimov (2017) evaluated the meat-bone paste (MBP) as an ingredient for meat batter and its effect on physicochemical properties and amino acid composition. They developed five formulations, a control and “four meat batters with different amounts of MBP, 10% (MBP-10), 20% (MBP-20), 30% (MBP-30) and 40% (MBP-40), respectively. The active acidity (pH) of the formulations was determined by potentiometry. Samples were analyzed for water binding capacity (WBC) by exudation of moisture onto filter paper following the application of pressure. The amino acid composition was determined by liquid chromatography.” (Kakimov, 2017)
Bone Paste Preparation
Kakimov (2017) summarises current processing methods as usually involving “grinding and hydrolysis of the bones, followed by treatment with various chemical reagents.” He references Berdutina and Antipova et al. who “describes the preparation of protein hydrolysates from bone that included fermentation and acid hydrolysis.” “For a study on the production of protein supplements,” Kakimov (2017) references Kutcsakov et al. who describes “hydrolysis of meat-bone raw material by hydrochloric acid followed by sodium hydroxide neutralization, defatting and drying.”
Yessimbekov (2021) mentions that a patent has recently been granted on one such process. “A patent was granted by the Republic of Kazakhstan #2202 on 15 June 2017 for the method developed by Kakimov et al.. Bone grinding processing by this procedure allows obtaining a meat-bone paste which is free of hard bone particles; thus, it results in a product that is smooth and soft to the tongue of the consumer.” (Yessimbekov, 2021)
“Bones with meat tissue were washed with cold water and then crushed into 50 –70mm long fragments. Cutting bones into small pieces was done manually with an axe. The bone fragments were stored at -18oC to – 20oC before loading into the hopper of a crushing machine equipped with an 8mm diameter meat grinder plate. The bone was ground and crushed again using a 3mm meat grinder plate; water was then added to a 1:1 ratio (w/w). The mixture was frozen at -3oC to -5oC for 1 h and then ground using a micro-milling machine having rotational knives spaced at 0.50mm. The resulting meat-bone paste (MBP) was used to prepare pâté meat batters.” (Yessimbekov, 2021)
Kakimov (2017), to study the meat-bone paste as an ingredient for meat batter and the effect on physicochemical properties and amino acid composition used bones with attached meat tissue and “washed [it] with cold water and then crushed [it] into 50-70 mm long fragments. The bone fragments were stored at 18-20°C before loading into the hopper of a crushing machine V2-FDB (Russia) equipped with an 8 mm diameter meat grinder plate. The bone was ground and crushed again using a 3 mm meat grinder plate, water was then added to a 1:1 ratio (w/w). The mixture was frozen at -3 – 5°C for 1 h and then ground using a Supermasscolloider MKZA-10-15 (Masuko Sangyo Co., Ltd, Kawaguchi, Japan) micromilling machine having rotational knives spaced at 0.5 mm. The resulting meat-bone paste (MBP) was used to prepare meat batters.”
The meat batter they prepared was done as follows. “Five meat batter formulations were prepared using varying amounts of MBP and prime and grade one beef from which all visible connective tissue was removed. The mixtures were then ground by passage through a meat grinder fitted first with an 8 mm plate and then a 5 mm plate. The basic composition of the meat batter was 50% prime beef, 35% grade one beef (together, a total of 85% beef), 10% ground boiled beans and 5% egg mélange. Then, MBP was substituted for the prime and grade one beef mixture at four amounts 10, 20, 30 and 40%, respectively. Meat batters were prepared in a mixer-cutter to which the minced meat, MBP, boiled beans, 2.5% sodium nitrite, egg mélange and water were added individually. All the ingredients were mixed and ground together for 5-10 min at 2-4°C. Salt was added to extract myofibrillar proteins, whereas egg mélange was included as an emulsifier to bind the meat batter components, as well as a source of unsaturated fatty acids and lecithin. For seasoning, peeled and minced garlic, granulated sugar, black or white pepper and coriander were added. Sodium nitrite was included as a preservative. After mixing, the meat batters were packed in polyethylene bags and stored at (-8°C).” (Kakimov, 2017)
The following table shows the composition of the different meat mixes.
Bone-Paste Particle Size
Yessimbekov (2021) reports that “as can be seen in the image of bone particles, magnified 50 times where the bone particle sizes were measured, particle sizes exceeding 0.40 mm (400 microns) were not detected.
Bone particle sizes of meat-bone paste by Yessimbekov (2021).
“On the basis of the sieve analysis of the meat-bone paste after grinding on a colloid machine with a gap between the grinding wheels of 0.10 mm, it was found that the mass fraction of bone particles ranging in size from 0.10 mm to 0.25 mm is more than 95%. Bone particles that were beyond 0.25 mm were less than 5% and, as mentioned, particles of 0.40 mm (or higher) were not detected. Similar findings were obtained in a previous study, in which the meat-bone particle size after grinding on the colloid mincing machine was from 0.20 to 1.5 mm, while after grinding on the superfine machine, the particle size was reduced to less than 0.10 mm. A more recent study concluded that after grinding in the masscolloider with a gap of 0.25 mm, the bone particle size ranged between 0.14 mm and 0.37 mm, while after using a masscolloider with a gap of 0.10 mm, the bone size decreased and ranged between 0.045 mm and 0.19 mm. These results agree with our findings, and they demonstrate that the process and conditions for obtaining the meat-bone paste are good and that this allows obtaining a meat-bone paste with a smooth texture, which is not perceptible by consumers, and which is digestible by humans. Therefore, the meat-bone paste obtained in this research can be used for the production or reformulation of meat products: in our case, liver pâté.” (Yessimbekov, 2021)
Results from Kakimov Meat-Bone Batters
“Proximate composition of the meat-bone paste (MBP) was determined. Relative to the base formulation (control), MBP had a higher ash level (15.99±0.18%) but a lower fat (4.35±0.06%) and protein (14.70±0.17%) content and a moisture level of 64.97±0.79%. The effect of increasing amounts of MBP on the proximate composition of meat batters (table above) was analyzed. At 40% MBP (MBP-40), the ash content significantly increased relative to the control (5.24 vs. 0.81%), whereas the protein and fat content steadily decreased with increasing amounts of MBP. In particular, the fat content of the control sample fat content was 16.50% but the MBP-40 batter had only 10.71% fat. Meanwhile, MBP-40 had a lower protein content than the control, which was slightly but not significantly, lower than that of MBP-10 (16.26, 17.49 and 17.67%, respectively). The moisture content of the samples ranged from 65.20 – 67.79% and there were no significant differences among the formulations. The energy value of meat batters steadily decreased with the addition of MBP, with MBP-40 having the fewest calories per 100 g.” (Kakimov, 2017)
“The ash content of the MBP-30 and MBP-40 formulations was markedly higher (4.18 and 5.24%, respectively) than the recommended amount for meat batters (approximately 3.5%). Similar trends in moisture, fat and protein (64.17, 17.83, 16.68%, respectively) content were observed in a study by Kahramanov for meat batters made from grade two beef, fermented meat trimmings and blood. Except for the ash content, the proximate composition of these meat batters was also similar to that observed by Kakimov, who developed a protein supplement (protein 15.39%, fat 12.94% and ash 1.41%) for meat batters consisting of bone fat, blood, egg mélange and ultrafine ground bone. In another study, Pershina showed that bone powder added to a sausage formulation that included beef, pork, milk and eggs resulted in sausages that had a lower protein content (12.0-14.0%) and higher fat content (18-22%), which both differed from those seen for this study. Krishnan and Sharma used offal meat (rumen and heart meat) to process cooked sausages that had a protein content similar to the MBP-40 formulation (16.39% vs. 16.26%), whereas meat patties composed of ground beef and 10% spleen tissue in a study by Bittel and Graham had significantly higher protein content (26%) than it was seen with our formulations. Overall, however, the proximate composition of the meat batter was consistent with that observed for previous studies.” (Kakimov, 2017)
WBC and pH Determination:
“The pH is an important parameter that can significantly impact sensory, microbiological, physicochemical and rheological characteristics of meat and meat products. The addition of MBP raised the pH of the meat batter, with more neutral pH values seen for MBP-40 vs. the control (6.20 vs. 7.26). This effect is likely because the MBP itself has a high pH (7.28). The WBC also changed with the addition of increasing amounts of MBP as evidenced by the sharp and significant increase in WBC of more than 15% between MBP-10 and MBP-20. The increase can be attributed to the high water binding capacity of MBP.” (Kakimov, 2017)
WBC and pHin meat batter with different proportions of meat-bone paste. (Kakimov, 2017)
Amino Acid Determination
“The MBP also changed the total amino acid content of the meat batter formulation. Amino acid composition of MBP showed the large amount of glycine (2556.28 mg/100 g), proline (1649.32 mg/100 g) and oxyproline (1360.75 mg/100 g).” (Kakimov, 2017)
“These amino acids constitute the major portion of collagen and play an important role in human body. With increasing amounts of MBP, the amino acid content of the meat batters decreased, whereas the formulation with the lowest amount of MBP, MBP-10, was statistically similar to that of the control (21.0 g/100 g vs. 21.1 g/100 g). The amount of non-essential amino acids such as glycine and proline were significantly increased by approximately 43 and 21%, respectively, in meat batters with 40% MBP.” (Kakimov, 2017)
“Notably, these two amino acids, along with the proline derivative oxyproline are the major constituents of collagen and have an important physiological role in that glycine participates in nitrogen metabolism and protein synthesis and also has a vital role in brain function. Meanwhile, proline is essential for muscle stamina, as proline deficiencies are associated with fatigue.” (Kakimov, 2017)
“Consumption of foods with high amino acid contents that can be used for collagen production will contribute to muscle development and regeneration. Overall, the essential amino acid content of meat batters prepared here conformed to the Food and Agriculture Organization of the United Nations (FAO) scale for ideal protein content (table above). However, in MBP-40 meat batters, the limiting amino acids were methionine and cysteine (amino acid score 97.3%) and tryptophan (AS 98.4%). Methionine is a major building block for proteins and is associated with vitamin B12 deficiency. Tryptophan boosts synthesis of the vitamin PP and deficiencies in this amino acid can lead to serious illnesses such as tuberculosis, cancer and diabetes.” (Kakimov, 2017)
“The highest amino acid score was seen for meat batters with 10% MBP. Increases in the amount of MBP were associated with decreasing amino acid scores (Table above). The highest amino acid score was calculated for lysine (175.96) in MBP-10 and this value decreased to 149.04 for MBP-40. Lysine is essential for bone formation and childhood development and also promotes calcium digestion and nitrogen metabolism in humans. Moreover, adequate lysine is critical for synthesis of antibodies and hormones as well as for collagen formation and tissue regeneration. The sum of the phenylalanine and tyrosine content for the control was around 50% higher than the FAO recommendation and the addition of MBP upto 40% decreased the value to a level that was closer to that of the FAO (Table Above).” (Kakimov, 2017)
“The approximate level of leucine and threonine in both the formation and the controls was higher than that of the FAO, although MBP-40 had the lowest amount. The MBP-40 also had the lowest amount of isoleucine relative to the control and was closest to the value set by the FAO (4.44 vs. 4.0). Isoleucine is essential for hemoglobin production and provides an energy source for muscle while also preventing early muscle fatigue. Threonine improves cardiovascular and immune system function and that of the liver. This amino acid is also involved in glycine and serine synthesis. Each of these amino acids is important for strengthening ligaments and all muscles, including the heart.” (Kakimov, 2017)
“Overall, these results indicate that the optimum quantity of MBP in meat batters ranges between 10 and 20% of total mass. Partial replacement of beef with a MBP can reduce production costs by as much as 15% while enriching meat batters with amino acids such as glycine, proline and oxyproline. However, excess amounts of MBP in meat batter formulations reduces their nutritive value and is inconsistent with regulations for meat products.” (Kakimov, 2017)
These results are highly significant and show the scientific basis for the inclusion of bone meal in products intended for human consumption. We reviewed equipment available for producing bone meal. The Kakimov study is key in understanding the probably/ optimal range for inclusion of bone meal in fine emulsion meat products.
As far as equipment is concerned, this validates the work of Green Cell Technologies and their Dynamic Cell Disruption Technology which can accomplish what smaller equipment can do at a far increased rate and efficiency. They have demonstrated their equipment is able to reduce particle size of bones smaller and more effectively than other technology and since comminution of meat particles is tightly related to digestibility through greater bio availability (Notes on Comminution and Digestibility) for large plants this must remain their number one consideration. In many western countries, its inclusion in human food will remain problematic till legislative reforms are affected. Until such time, as far as bone meal is concerned, such technology’s main area of application will remain directed to the animal feed industry. Countries with greater sanity in legislation will have the opportunity to exploit technology like this to the direct benefit of their citizens through its inclusion into food for human consumption.
Kakimov, A., Suychinov, A., Mayorov, A., Yessimbekov, Z., Okuskhanova, E., Kuderinova, N., and Bakiyeva, A.. (2017) Meat-bone Paste as an Ingredient for Meat Batter, Effect on Physicochemical Properties and Amino Acid Composition
Paloheimo, L., Björkenheim, L. M., Leivonen, H.. (1965) STUDIES ON THE MAIN CHEMICAL COMPOSITION OF BONES, Department of Animal Husbandry, University of Helsinki, Journal.fi, Received January 2, 1965
Yessimbekov, Z., Kakimov, A., Caporaso, N., Suychinov, A., Kabdylzhar, B., Shariati, M. A., Baikadamova, A., Domínguez, R., Lorenzo, J. M.. 2021. Use of Meat-Bone Paste to Develop Calcium-Enriched Liver Pâté. Foods 2021, 10, 2042. https://doi.org/10.3390/foods10092042
Creating the Optimal Frankfurter Style Sausage in Africa: Hungarians and Russians
by Eben van Tonder
27 November 2021
Over the years I have written about the history of the development of Russian sausages in South Africa (Origins of the South African Sausage, Called a Russian). I’ve created poems about it! 🙂 (Ode to the Russian Sausage – a Technical Evaluation) It is a South African frankfurter style sausages. In Australia, it is called a Kransky and in Zambia and parts of the DRC, it is called a Hungarian. A Hungarian is made without showpieces which means that the exact same product in South Africa is called a smokey or a penny polony. The basic formulations are, however, the same. It is a fine emulsion sausage.
I have looked at every aspect of Russian/ Hungarian making except cooking/ smoking and packing it. This week attention shifted to these final aspects. Daniel Erdei from the smokehouse producer Kerres visited me in South Africa. Their new hybrid smoke system, combining vertical and horizontal airflow systems make them, in my opinion, the best option in the world. They claim a reduction of 30% in cooking/ smoking loss.
Apart from smoking/ cooking, I looked at packaging with shelf life in mind. Many of the large producers in South Africa opted for High-Pressure Pastorisation over the last few years following the Listeriosis epidemy. It is an extremely expensive solution, and I was keen to see what else is on the market.
In South Africa there are several producers who manufacture between 60 and 100 tons of these sausages per day and the economic benefit of this consideration can hardly be overrated. Besides these, current projects underway in other African countries will soon see the same production levels from other African regions. This, coupled with the devastating effects of Covid on international food prices makes the work urgent.
The danger and impact of Covid were highlighted to us while we were in Simons Town, at the famous Brass Bell-Inn and Daniel, a German citizen, started getting calls from family and from the management at Kerres as they were scrambling to get him on the first available flight out of South Africa after the discovery of a new Omicron variant (Variant B.1.1.529) and as countries from around the world were announcing the immediate cancellation of flights from and into South Africa.
After the logistics were arranged and we were satisfied that the best measures were taken to ensure his speedy return to Germany, we continued with our adventure while designing the optimal Russian/ Hungarian line and processing approach.
The following discussion points were all highlighted and interrogated yesterday.
Novel Processing Techniques
– DCD Technology from Green Cell
Work done with DCD Technology (The Power of Microparticles: Disruptor (DCD) Technology) shows the feasibility to use nutritious parts of an animal carcass previously not included in raw material for such sausages. DCD has proven to be extremely important even though it was shown to be less effective in certain specific areas of application (Muscle Structure (Biology)). For large throughput factories it, however, is an ideal solution to increase the overall digestibility of certain raw materials since digestibility is closely related to comminution (Notes on Comminution and Digestibility). It also offers a way to apply pressure for micro control in a way that was previously only possible with HPP or similar systems (for example pulse technology). Two years of intensive work showed that DCD technology has a definite place in meat processing. A proper understanding of its strengths and weaknesses, along with alternative processing techniques that we developed for certain areas of application allows us to create our own MDM/ MSM. MDM or MSM is widely used in Africa as the basis for these sausages (MDM – Not all are created equal!). The MDM-replacer we created has been shown to be more nutritious compared to MDM, imported from, for example, South America and has greater functionality than using MDM alone.
– Binding of water
Water act as the plasticizer in the system. The meat’s texture in these sausages “is due to its property of heat-induced long-chain gelling or setting” and the “cooked meat is classifiable as a water-plasticized, filled-cell mixed-composite thermosetting plastic biopolymer. The word “polymer” denotes long-chain macromolecules which are crosslinked, such as proteins or starches. The word “plasticizer” indicates that water is the filling solvent that hydrates the polymer and supports its “plastic” behaviour.” (Review of comminuted and cooked meat product properties from a sol, gel and polymer viewpoint)
The optimal binding of water has been shown to be a balance between the creation of various base emulsions (for example fat and skin emulsions) and the inherent requirement for water as the plasticizer. In other words, there is a certain amount of water required to form the gel which is the basis of the product – all other water is better pre-bound. Adding “fillers” with high water-holding capacity such as soy isolate or TVP serves an important function of making the sausage less “rubbery”. LaBudde (1992) states it as follows. “Fillers with high water-holding capacity will effectively de-plasticize the system, resulting in lower strains to failure and higher stresses.” (Review of comminuted and cooked meat product properties from a sol, gel and polymer viewpoint). Like in whole muscle chemistry, we are looking at the role of bound, immobilized, and free water in the sausage matrix (see the section under “water” in Muscle Structure (Biology)
– Losing Some of the Water
Managing the process of water loss is of the utmost importance. Water act as the plasticizer in the system. In a frankfurter style sausage, “the proteins are gelled not only through the heat of cooking, but also through the mechanisms of water loss (shrinkage), pH (acid rinse) and smoke application.”
That water loss must take place and is important. “The effect of moisture loss through shrinkage is twofold: a drop in the plasticizer percentage and an increase in the percentage of other materials, including protein. Consequently, the strength of a “shrunk” product will be larger than that of the “unshrunk” product by at least the percentage shrink [ 1/(1-s) ], and the strain to failure lower by approximately the shrink [ 1-s ].” (Review of comminuted and cooked meat product properties from a sol, gel and polymer viewpoint)
Water loss is important but too much water loss is uneconomical. In the right drying, smoking and cooking chamber, the method of applying heat to the sausages, the rate of temperature application, humidity and wind speed (velocity) are key factors to control. From a business perspective, the role of an excellent personal banker is key to success. In terms of meat processing, the right smokehouse partner is as important as a personal banker to the overall business. They must be entrusted with the management of water or fat loss during the final cooking step. They are also the custodians of the final look of the product before packaging. Texture and gel formation is within their scope of responsibility. I cannot over emphasis the importance of choosing the right smokehouse and the right smokehouse supplier.
In producing these sausages, a customary South African formulation will result in between 15% and 18% moisture loss during the cooking cycle to 71o C. Kerres smokehouses technology promises a 30% reduction in this loss to between 10 and 13%. Trails are underway in Germany, using South African recipes, to confirm these. The overall loss we are targeting by using the correct product ingredients, along with the Kerres smokehouse technology I set at between 8% and 10%. These targets are ambitious, and results will be made available in updates of this article.
Old School Smoking/ Drying -> Latest Technology
“Kerres smokehouses technology promises a 30% reduction in smoking/ cooking loss”
Blending and Filling
The grinder -> mixer -> emulsifier -> filler configuration is retained with key adjustments in the state of the ingredients added at the various stages. The entire discussion of the mix of traditional processing technology using micro cutters and grinders and incorporating DCD’ed raw materials discussed above feature prominently under this heading. For Africa, I advocate the incorporation of Ethyl Lauroyl Arginate (LAE) in the product as one of the micro hurdles.
There is a trend in the rest of Africa (excluding South Africa) not to dry the sausages before sale and to use liquid smoke in the product composition instead of natural smoke. This is an unacceptable compromise because it seriously compromises the product quality, and our goal is to deliver more nutritious food to Africa of a quality equal to or higher than what is found in European and North American supermarkets in Frankfurter sausages.
I have found the Kerres team to be the best to outsource the final look, feel and texture of the product to. I base this statement on the versatility of their equipment. It is a familiar frustration to all production managers that they buy equipment and lock themselves into a certain processing system which invariably comes to haunt them later when they want to change the production system. In smokehouse technology, it is clearly seen in the choice between a system with vertical or horizontal airflow.
As a case in point, consider the change from natural or artificial casings and the emergence of alginate casing technology. The use of alginate casing technology has become widely available, in South Africa, through the spice supplier Freddy Hirsch, but when drying, the sausages can’t hang and are packed on trays which favours a horizontal airflow and not the vertical airflow systems used when smoking sausages that hang on smoke sticks and are linked together. So, ineffective smokehouses now become an obstacle when the production manager wants to change how the sausages are produced.
Even more, what do you do if you only want to change part of the processing system to alginate casings and still offer the consumers the natural or collagen casings they are used to?
The same applies to bacon processing technology. The traditional way is to hang the bacon in the smoke chamber. However, the latest method of bacon processing using grids to “shape” the bacon, favours again a horizontal airflow system as opposed to the vertical flow systems. The latter is favoured by the traditional way of hanging the bacon. (Best Bacon and Rib System on Earth)
Because drying/ cooking/ smoking is so important in the final product, it is surprising that many owners/ investors or managers base their decision on “an easy deal” or the cheapest option available to them. The wrong smokehouse partners are one of the most expensive mistakes we’ve made at Woody’s!
The Kerres smoker has a hybrid system that incorporates both horizontal and vertical airflow. They offer it as an added option, but in my mind, it is an easy decision!
Drying and smoking are dependent on many factors. Airflow is amongst the most prominent features. Below is a clip showing the Kerres system. The hybrid system is a stroke of genius. This system along with an introduction to the smokehouses of Kerres is dealt with in the video clip below.
Demonstrating the effectiveness of the hybrid smoking system
Below is a clip from a client of Kerres in the USA. Whether alginate casings are used for sausage production, or the grid system in bacon processing, the hybrid system is the best solution I ever came across. The clip below which I got from their website is absolutely astounding! See how close the shelves are stacked and how full they are loaded and have a look at the consistency! It is without a doubt the single most impressive display of what can be achieved in a smokehouse than I have ever seen!
Vegetable sausages are nothing new to areas in the middle east, but the West has suddenly woken up to this important product class when it realised its heavy reliance on meat-based diets presents health challenges that cannot be overcome apart from reducing the consumption of meat.
This area of application represents a feature of DCD Technology that cannot be achieved more effectively in any other way. Let me state it like this. DCD technology makes the high throughput production line of such sausages possible. It speaks to the essence of the approach I followed in re-evaluating the production of hybrid sausages two years ago (Nose-to-Tail and Root-to-Tip: Re-Thinking Emulsions).
The matter of final product packaging and shelf life is closely related as is shelf life and raw materials used in the blending and filling stage. In general, shelf life will be achieved through:
Level of water binding achieved;
Pressure from the DCD processing system of Green Cell on key ingredients;
The use of LAE both included into the meat mix as well as fogging the roll stock pouch after forming and fogging into the pouch after packing.
If applied correctly, this natural preservative will extend the product shelf life dramatically. The key to the effectiveness of the product is dosage and application method which we are in the process of addressing. Watch this space for updates and announcements!
Using the combined approach as outlined above yields unsurpassed shelf-life results.
Over the years I have seen the tremendous benefit in stepping periodically back from one’s work and re-evaluating everything I have learned and asking the question if there is not a better way of doing it. This is true when it comes to bacon production technology (Best Bacon and Rib System on Earth). I have not yet integrated a new application of the Kerres smoker technology to the article I just cited on bacon production, but I will do this over the weeks following and publish it as new and updated articles.
In our current consideration of the best Frankfurter style sausage system available, the Kerres smokehouse technology, along with LAE and DCD Technology draws years of work together into a complete and extremely versatile and productive system.
Africa is emerging as the future economic powerhouse and the driver of world markets, and I am honoured to be a small part of this awakening when it comes to meat processing technology.
We are considering source material for fine emulation usages. Collagen has become my main area of interest. Here I post the relevant data related to collagen. It is my personal study notes if you will.
“Collagen is a fibrous protein found in all multicellular animals (Voet et al., 2006). It is an important component in the support structures in vertebrates and invertebrates. It is the most abundant protein in mammals, corresponding to approximately 25% of the weight of all proteins (Ward and Courts, 1977; Voet et al., 2006), and is the major constituent protein of skin, tendons, cartilage, bones and tissues in general. In poultry and fish it plays a similar role to that of invertebrates and is an important component of the body wall (Ward and Courts, 1977).”
“Collagen molecules are about 280 nm long, with a molar mass of 360,000 Da; they are stabilized by hydrogen bonds and intermolecular bonds (Silva and Penna, 2012), which are composed of three helical polypeptide chains, each with about 1000 amino acids, which are called an α chain. The chains become entangled, forming a stable triple helix which is varied in size. The triple helix molecules have terminal globular domains and are called procollagen. These globular regions are cleaved in varying degrees to give a polymerized structure (tropocollagen), which is the basic unit of collagen. The tropocollagen molecules are stabilized by hydrophobic and electrostatic interactions (Nelson and Cox, 2004; Damoradan et al., 2010).” (Schmidt, et al., 2016)
“There are different kinds of collagen in vertebrates; they typically contain about 35% glycine (Gly), 11% alanine (Ala) and 21% proline (Pro) and hydroxyproline (Hyp). The amino acid sequence in collagen is generally a repetitive tripeptide unit (Gly-X-Y), where X is frequently Pro and Y is Hyp (Nelson and Cox, 2004).” (Schmidt, et al., 2016)
“At least 29 different types of collagen have been reported, which are classified according to their structure into: striatum (fibrous), non-fibrous (network forming), microfibrillar (filamentous) and those which are associated with fibril (Damoradan et al., 2010).” (Schmidt, et al., 2016)
“Type I collagen is the most common, primarily in connective tissue, in tissues such as skin, tendons and bones. It consists of three polypeptide chains, two of which are identical, which are called chain α1 (I) and α2 (I), and which are composed of different amino acids. Type II collagen occurs almost exclusively in cartilage tissue and it is believed that the α1 (II) subunit is similar to the α1 (I) subunit. Type III collagen is strongly dependent on age: very young skin can contain up to 50%, but with the passage of time that percentage can be reduced to 5-10%. Other types of collagen are only present in very small quantities, mainly in specific organs such as the basement membranes, cornea, heart muscle, lungs and intestinal mucosa (Schrieber and Gareis, 2007; Karim and Bhat, 2009).” (Schmidt, et al., 2016)
Collagen as a Constituent of Mammalian Tissue
“Mammalian tissues have many things in common. For example, they usually consist of cells embedded in a matrix consisting of collagen, elastin, and mucopolysaccharides. The interactions of these components give the tissue its structural properties, while the cells embedded in the matrix give the tissue its metabolic properties. The proportion of matrix present depends on the tissue function so that structural tissue (e.g. skin, bone or tendon) consists mainly of connective tissue, while tissues with a major metabolic function (e.g. liver or brain) contain little connective tissue.” (Courtis and Ward, 1977)
“Neuman and Logan (1950) based the collagen and elastin contents on hydroxyproline determinations of preparations similar to those of Lowry, assuming collagen contains 13.4% hydroxyproline and elastin contains 2% hydroxyproline. While the former assumption is substantially true (modern literature favours a hydroxyproline value of 14.4% in collagen) the existence of hydroxyproline in elastin is not now accepted with certainty.” (Courtis and Ward, 1977)
“More recently Dahl and Persson (1963) have estimated the hydroxyproline content of several tissues by direct tissue hydrolysis, and their results can be converted to values of collagen content if one assumes that all the hydroxy-proline is derived from collagen. The table below shows how some of these results have been collected in order to indicate what may be regarded as typical values. Since in no case did the author give precise details of the tissues used, the table should be considered only as a guide to collagen-rich tissues.” (Courtis and Ward, 1977)
The table above is very interesting as it gives potential sources of collagen which suppliers can rank in price in order to determine the cost of collagen. In bovine, collagen-containing material can therefore be ranked as follows:
Hydroxyproline becomes the market to indicate a high usage of collagen. Irrespective of the animal species, collagen fibres have an amino acid composition in which glycine makes up around one-third of the total residues and the amino acids proline and hydroxyproline a further 15-30%. “Hydroxyproline is of very limited occurrence in proteins, the only other mammalian protein in which it occurs being elastin (2 %). Collagen is also the only protein reported to contain more than about 0.1 % hydroxy-lysine.” (Courtis and Ward, 1977) The presence of hydroxyproline is the marker used to determine the approximate inclusion of collagen into meat products. “Hydroxyproline is a part of collagen and occurs only in sinews, bones, gristle and skin.” (Buchi) It is therefore taken that a high percentage of hydroxyproline is indicative that a large percentage of collagen was added to the meat formulation.
Elastin is the main protein component of the elastic fibres, and differs from proteins in that it has no triple-helical collagen-like domain. Nevertheless, the polypeptide chain has repeated -Gly-X-Y sequences, which contain 4-hydroxyproline but no hydroxylysine. The 4-hydroxyproline content of elastin may vary greatly, usually being about 10 to 15 residues per 1000 amino acids, but ranging up to about 50 residues per 1000 in special situations.
When solutions of collagen are heated at about 40°C or above, denaturation occurs and the helical structure is lost. (Courtis and Ward, 1977)
Reactivity of Collagen
“The reactive amino acid side chains all project outwards from the main body of the triple helix and in soluble collagens should, therefore, be accessible to all chemical reagents. In the compact fibrous forms of collagen, however, there is no guarantee that this will be so.” (Ward and Courtis, 1977) Overcoming this is the main purpose behind my study!
“Native collagens, even the soluble forms, are very resistant both to the action of enzymes and chemicals, a property almost certainly related to the stable helical conformation of the molecule and the protection this affords to the peptide bonds of the individual chains.” (Ward and Courtis, 1977)
“Dilute acids lead to solubilization of varying amounts of collagen and on the basis of current hypotheses, this would appear to be due to the action of the acid on labile intermolecular links of the Schiff’s base type. Attack on the collagen molecule itself appears to be negligible even at low pH values provided the temperature is below 20°C.” (Ward and Courtis, 1977)
“A long treatment in alkali is the traditional prelude to the conversion of collagen to gelatin. Complete breakdown of native collagen to small peptides can only be achieved by the action of a group of bacterial enzymes, the collagenases, the best documented being that isolated from Cl. histolyticum (see Mandl, 1961). These enzymes are specific for the -Gly-Pro-X-Gly-(Pro or Hypro-) sequence, cleavage occurring to give an N-terminal glycine. Even with such enzymes, however, complete solubilization and breakdown of many collagenous tissues, e.g. mature ox hide collagen is difficult. Tadpole collagenase is even more specific in its action.” (Ward and Courtis, 1977)
Chang et al. (2011), investigated the effects of heat-induced changes in intramuscular connective tissue (IMCT) and collagen on meat texture properties of beef Semitendinosus (ST) muscle. Their conclusions are instructive. They compared heating in a water bath and microwave heating.
-> Collagen Content
They found that “the mean content for total collagen of the raw meat was 0.66 ± 0.09 % (wet basis) and was within the normal range (lower than 1% wet weight). Total collagen content of microwave treated sample was higher compared to water bath treatment before heating temperature up to 80◦C, and showed significant differences (p 0.05) were found for soluble collagen content between water bath and microwave treated samples, and the same changes tendency were presented as total collagen content with increase in the temperature during water bath and microwave heating.” (Chang et al., 2011)
-> Collagen Solubility
“Changes of collagen solubility of water bath and microwave treated samples were irregular. There was an unaccountable variation in collagen solubility with a maximum at 75◦C for water bath heated meat. Collagen solubility changed unaccountably throughout heating due to juice loss and collagen solubilization. For microwave heating, the highest collagen solubility was found when heated to 90◦C, and could be attributed to the conversion of collagen to gelatin occurs at this temperature range. At 65◦C, collagen solubility of water bath and microwave treated samples were relatively higher simultaneously, partly because of the shrinkage effect of perimysial and endomysial collagen at about 65◦C (proved in DSC analysis, data not shown). According to the reports of Li et al., low correlations were found between meat-Warner-Bratzler shear force (WBSF) values and total collagen and collagen solubility, although previous data indicated a high relationship between peak shear force and collagen content for beef.” (Chang et al., 2011)
We will return to the solubility of collagen when we look at soluble collagen chemistry.
-> Instrumental Texture Profile Analysis (TPA)
“TPA provides textural change of meat during thermal treatment. It was found that the thermal conditions (internal temperature) and heating modes had significant effects on all the TPA parameters of meat except for resilience (Fig. 1G). Hardness, as a measure of force necessary to attain a given deformation, gave a different response to the different heating methods and temperatures applied. Hardness (Fig. 1A) of microwave treated sample was higher compared to water bath treatment at 65◦C, and showed significant differences (p < 0.05) in the temperature range from 75◦C to 90◦C. Hardness of water bath heated meat showed a maximum at 60◦C. Changes of adhesiveness (Fig. 1B) for water bath and microwave treated sample were irregular with increase in internal core temperatures, and there were no significant differences except for 75◦C between both thermal treatments.” (Chang et al., 2011)
“Springiness is an important TPA parameter and the date on springiness (Fig. 1C) for microwave heated meat had a changing point at 65◦C, and the meat springiness of water bath heated was higher compared to microwave treatment after 65◦C. This parameter seems to be affected by myosin and α-actinin denaturation, which occurs in this temperature range. Springiness of meat is likely related to the degree of fiber swelling which in turn should be reflected in the fiber diameter. As discussed above, the main changes of springiness during heating were consistent with the thermal shrinkage of intramuscular collagen at around 65◦C.” (Chang et al., 2011)
“Cohesiveness contributes to the comprehensive understanding of viscoelastic properties including tensile strength. Chewiness is the energy required to masticate a solid food product to a state ready for swallowing. Therefore, it is considered as an important parameter since the final phase of mouth feels and the ease in swallowing depends on the chewiness of meat. Cohesiveness (Fig. 1D), gumminess (Fig. 1E), chewiness (Fig. 1F), and resilience (Fig. 1G) were all showed a maximum at 65◦C in microwave treated sample, however, gumminess and chewiness of water bath treatment reached the maximum at 60◦C. Changes of cohesiveness and resilience for water bath treated sample were irregular with the increase in heating temperature, it was maybe result from the intercorrelation effects among TPA parameters during the long time heating for water bath compared with the microwave. Resilience was the only TPA parameter that presented no significant differences between two thermal treatments.” (Chang et al., 2011)
“Changes of TPA parameters in this study suggested that internal core temperature of 60◦C and 65◦C were the critical heating temperatures which affect meat texture for water bath and microwave heating respectively. Furthermore, according to our previous studies, the maximal shrinkage temperature of IMCT collagen was within this range, this can give a full relationship of heat-induced change of collagen to meat quality, especially the meat texture; the results were also clearly showed in the SEM photographs.” (Chang et al., 2011)
“The swelling of collagen fibres in tissues such as tendon or skin is of two types: osmotic and lyotropic (see Gustavson, 1956). The first occurs in acid or alkaline solutions and is related to the positive or negative charge on the protein reaching a maximum at pH 2-0 and 12-0 and then decreasing again at more extreme pH values at the rising ion concentration reduces the change effect. The fibres swell laterally, contract in length and become glassy and translucent in appearance. The swelling is reversed by neutralization, by the addition of salts which reduce the effect of charge or by the presence of anions (or cations) having a specific affinity for the charged groups. This type of swelling has been considered in terms of the Donnan equilibrium (Procter and Wilson, 1916) which provides a satisfactory explanation in practical terms. X-ray diffraction studies (Burge et al., 1958) showed that the lateral spacing of about 11 Å, attributed to the distance between the molecules, was increased to 13-5 Å in salt free water in the pH range of minimum swelling but increased to 15Å at pH 2-0. Structural stability, as indicated by fall in shrinkage temperature, is also affected, suggesting that water actually penetrates into the tropocollagen molecule, but it is difficult to disentangle the effects of swelling, pH and ion concentration.” (Courtis and Ward, 1977)
“Swelling in neutral salt solutions has rather different effects. The fibres become opaque and flaccid, length is relatively unaffected and cohesion between fibrils is reduced. The uptake of water varies greatly with the salt, increasing with its tendency to disrupt hydrogen bonds. Dimensional changes probably first occur in the less ordered polar areas of the molecule leading to more general disruption under favourable conditions, i.e. rise of temperature. (For fuller discussion of the effect of salts on the collagen triple helix see von Hippel, 1967.)” (Courtis and Ward, 1977)
Soluble Collagen Chemistry
“Varying amounts of fibrous collagen dissolve in cold acidic or near neutral buffers or even water. This material is referred to as soluble collagen and usually represents only a small fraction of total collagen present in any tissue. However, soluble collagen has provided the sample used for most studies concerned with the chemistry of collagen.”
“It has been known for some time that a part of mammalian collagen from tendon and from many other tissues can be extracted by dilute aqueous solutions of organic acids or buffered citrate of pH 3–4, while most of the collagen remains insoluble. There is in addition a quantitatively minute fraction which can be extracted at neutral or slightly alkaline pH by salt solutions and this has been called “neutral-salt-soluble collagen.” It has been suggested (Green and Lowther, 1959; Jackson and Bentley, 1960) that there are no sharp divisions between these different soluble fractions and that there is a continuous spectrum of molecular species varying in degree of aggregation and cross-linking.” (Munro (Ed), 1964)
“Soluble collagen chemistry dates back to the studies by Zachariades (1900) who observed swelling of tendons immersed in weak acid solutions.” (Fishman, 1970) Let’s look into the significance of swelling. Collagen is classed as “a naturally occurring matrix polymer.” (Cheema, 2011) When a polymer dissolves, the first step is a slow swelling process called solvation in which the polymer molecule swells by a factor 𝛿, which is related to CED. Linear and branched polymers dissolve in a second step, but network polymers remain in a swollen condition. (Carraher, 2003)
Polymer mobility is an important aspect helping to determine a polymer’s physical, chemical, and biological behaviour. Lack of mobility, either because of interactions that are too swift to allow the units within the polymer chain some mobility or because there is not enough energy (often a high enough temperature) available to create mobility, results in a brittle material. Many processing techniques require the polymer to have some mobility. This mobility can be achieved through application of heat and/or pressure, or by having the polymer in solution. Because of its size, the usual driving force for the mixing and dissolving of materials is much smaller for polymers in comparison with smaller molecules. Here we will look at some of the factors that affect polymer solubility. The physical properties of polymers . . . are related to the strength of the covalent bonds, the stiffness of the segments in the polymer backbone, and the strength of the intermolecular forces between the polymer molecules. The strength of the intermolecular forces is equal to the CED, which is the molar energy of vaporization per unit volume. Since intermolecular attractions of solvent and solute must be overcome when a solute dissolves, CED values may be used to predict solubility. (Carraher, 2003)
“A polymer dissolves by a swelling process followed by a dispersion process or disintegration of the swollen particles. This process may occur if there is a decrease in free energy. Since the second step in the solution process involves an increase in entropy, it is essential that the change in enthalpy be negligible or negative to assure a negative value for the change in free energy.” (Carraher, 2003)
“Soluble collagen chemistry was taken up again (following Zachariades, 1900), principally by Nageotte (1927a – e, 1928, 1930, 1933), Nageotte and Guyon (1933 and 34), Huzella (1932), Leplat (133a, b), Faure-Fremiet (1933a, b) and Guyon (1934). These authors worked with the dilute acid extracts and demonstrated a protein content.” (Fishman, 1970)
“Much of the knowledge of soluble collagen chemistry derives from initial papers by Tustanowski (1947) and Oreskovich, et al. (1948a, b) who demonstrated a revisable solubility of collagen fibrils that had dissolved in citric acid buffer (ph 3 – 4.5) and underwent reformation into collagen fibrils upon dialysis against water.” (Fishman, 1970)
Application of Soluble Collagen Chemistry
“There is a growing interest in the extraction process of collagen and its derivatives due to the growing tendency to use this protein to replace synthetic agents in various industrial processes, which results in a greater appreciation of the by-products from animal slaughter. Collagen’s characteristics depend on the raw material and the extraction conditions, which subsequently determine its application. The most commonly used extraction methods are based on the solubility of collagen in neutral saline solutions, acid solutions, and acid solutions with added enzymes. Recently, the use of ultrasound, combined with these traditional processes, has proven effective in increasing the extraction yield.” (Schmidt, et al., 2016) Schmidt, et al., 2016 did a mini review of the “different collagen extraction processes, from raw materials to the use of combinations of chemical and enzymatic processes, as well as the use of ultrasound.” The information outlined in their review has been collected from different national and international journals in Agricultural Sciences and Science and Food Technology. They studied the different extraction processes, using four bibliographic databases and also some books of renowned authors, and selected articles published between 2000 and 2015. (Schmidt, et al., 2016)
Raw materials for collagen extraction
“Meat is the main product derived from the slaughter of animals, while all other entrails and offal are classed as by-products (Bhaskar et al., 2007), including bones, tendons, skin, fatty tissues, horns, hooves, feet, blood and internal organs. The yield of by-products that is generated depends, among other factors, on the species, sex, age and body weight of the animal. The yield varies from 10% – 30% in cattle, pigs and sheep and from 5% – 6% in poultry (Nollet and Toldrá, 2011). According to Bhaskar et al. (2007) about 40% of these by-products are edible and 20% are inedible.” (Schmidt, et al., 2016)
“Depending on the culture and the country, edible by-products can be considered as waste or as delicacies that command high prices (Toldrá et al., 2012). However, the majority of by-products are not suitable for human consumption due to their characteristics. As a result, a potential source of income is lost, and the cost of disposal of these products has become increasingly high (Jayathilakan et al., 2012). Nevertheless, there is a growing awareness that these by-products can represent valuable resources if they are used properly.” (Schmidt, et al., 2016)
“Generally, inedible by-products are used in the manufacture of fertilizers, animal feed and fuel but there is also a growing market in using them to obtain minerals, fatty acids, and vitamins and to obtain protein hydrolysates and collagen. Obtaining those products, which have high added value, is a better alternative to use these by-products, which would otherwise be discarded.” (Schmidt, et al., 2016)
“The main sources for collagen extraction are byproducts from the slaughter of pork and beef (Jia et al., 2010; Silva and Penna, 2012). Several of these by-products have been studied, including the Achilles tendon (Li et al., 2009), pericardium (Santos et al., 2013), bovine inner layer of skin (Moraes and Cunha, 2013) and bovine bones (Paschalis et al., 2001), porcine skin (Yang and Shu, 2014) and porcine lung (Lin et al., 2011).” (Schmidt, et al., 2016)
“Recent research has examined alternative sources for the extraction of collagen, with particular emphasis on fish by-products (Muralidharan et al., 2013; Kaewdang et al., 2014; Ninan et al., 2014; Wang et al., 2014; Mahboob, 2015; Tang et al., 2015). This is mainly due to religious restrictions, regarding the non-consumption of pork by Muslims and Jews, and also the risk of bovine spongiform encephalopathy (BSE) (Kaewdang et al., 2014). The latter belongs to a family of diseases known as transmissible spongiform encephalopathies, which are caused by the accumulation of the pathological prion protein (PrPSc) in the brain and central nervous system, which affects adult bovines (Callado and Teixeira, 1998; Toldrá et al., 2012).” (Schmidt, et al., 2016)
“The extraction of collagen from fish has been carried out in several species using different byproducts, such as Japanese sea bass skin (Lateolabrax japonicus) (Kim et al., 2012), skin of clown featherback (Chitala ornata) (Kittiphattanabawon et al., 2015), bladder of yellow fin tuna (Thunnus albacares) (Kaewdang et al., 2014), skin and bone from Japanese seerfish (Scomberomorous niphonius) (Li et al., 2013), cartilage from Japanese sturgeon (Acipenser schrenckii) (Liang et al., 2014), and the fins, scales, skins, bones and swim bladders from bighead carp (Hypophthalmichthys nobilis) (Liu et al., 2012). Despite the extraction of marine collagen is easy and safe this collagen presents some limitations in their application, due to its low denaturation temperature (Subhan et al., 2015).” (Schmidt, et al., 2016)
“The extraction of collagen from poultry slaughter waste has also been researched, but with less emphasis because of the risk of the transmission of avian influenza (Saito et al., 2009). Studies have been performed regarding emu skin (Dromaius novaehollandiae) (Nagai et al., 2015), and chicken feet (Saiga et al., 2008; Almeida et al., 2012a; Hashim et al., 2014), chicken sternal cartilage (Cao and Xu, 2008), chicken skin (Cliche et al., 2003; Munasinghe et al., 2015) and chicken tarsus (Almeida et al., 2012b) etc.” (Schmidt, et al., 2016)
“The processing of by-products can convert a product with low value, or one that requires costly disposal, into a product that is able to cover all the costs of processing and disposal, with consequent higher added value and reduced environmental damage (Toldrá et al., 2012).” (Schmidt, et al., 2016)
Collagen extraction process
“Collagen can be basically obtained by chemical hydrolysis and enzymatic hydrolysis (Zavareze et al., 2009). Chemical hydrolysis is more commonly used in industry, but biological processes that use the addition of enzymes are more promising when products with high nutritional value and improved functionality are required (Martins et al., 2009). Moreover, enzymatic processes generate less waste and may reduce the processing time, but they are more expensive. To extract collagen it is necessary to remove numerous covalent intra- and intermolecular cross-links, which primarily involves residues of lysine and hydroxy-lysine, ester bonds and other bonds with saccharides, all of which makes the process quite complex (Ran and Wang, 2014).” (Schmidt, et al., 2016)
“Before the collagen can be extracted a pretreatment is performed using an acid or alkaline process, which varies according to the origin of the raw material. The pre-treatment is used to remove non-collagenous substances and to obtain higher yields in the process. The most commonly used extraction methods are based on the solubility of collagen in neutral saline solutions, acidic solutions, and acidic solutions with added enzymes. The table below presents a summary of the procedures employed in the extraction of collagen from animal by-products.” (Schmidt, et al., 2016)
“Due to the nature of the cross-linked collagen that is present in the connective tissue of animals, it dissolves very slowly, even in boiling water. As a result, a mild chemical treatment is necessary to break these cross-links before extraction (Schreiber and Gareis, 2007). To this end, diluted acids and bases are employed, and the collagen is subjected to partial hydrolysis, which maintains the collagen chains intact but the cross-links are cleaved (Prestes, 2013).” (Schmidt, et al., 2016)
“In the acidic form of pre-treatment, the raw material is immersed in acidic solution until the solution penetrates throughout the material. As the solution penetrates the structure of the skin at a controlled temperature it swells to two or three times its initial volume and the cleavage of the non-covalent inter- and intramolecular bonds occurs (Ledward, 2000). The acidic process is more suitable for more fragile raw materials with less intertwined collagen fibres, such as porcine and fish skins (Almeida, 2012b).” (Schmidt, et al., 2016)
“The alkaline process consists of treating the raw material with a basic solution, typically sodium hydroxide (NaOH), for a period that can take from a few days to several weeks (Prestes, 2013). This process is used for thicker materials that require a more aggressive penetration by the treatment agents, such as bovine ossein or shavings (Ledward, 2000). NaOH and Ca (OH)2 are often used for pre-treatment, but NaOH is better for pre-treating skins because it causes significant swelling, which facilitates the extraction of collagen by increasing the transfer rate of the mass in the tissue matrix (Liu et al., 2015).” (Schmidt, et al., 2016)
“A study by Liu et al. (2015) evaluated the effect of alkaline pre-treatment on the extraction of acid-soluble collagen (ASC) from the skin of grass carp (Ctenopharyngodon Idella). Concentrations of NaOH from 0.05 to 0.1 M were effective in removing non-collagenous proteins without losing the ASC and structural modifications at temperatures of 4, 10, 15 and 20°C. However, 0.2 and 0.5 NaOH M caused a significant loss of ASC, and 0.5 M NaOH resulted in structural modification in the collagen at 15 and 20°C. In addition to the use of acids and bases, enzymes or chemicals may also be used to cleave the cross-linked bonds to obtain products with different characteristics (Schrieber and Gareis, 2007).” (Schmidt, et al., 2016)
“In the extraction of collagen which is soluble in salt, neutral saline solutions are used, such as sodium chloride (NaCl), Tris-HCl (Tris (hydroxymethyl) aminomethane hydrochloride), phosphates or citrates. Caution is required in this process in order to control the concentration of salt, but considering that the majority of collagen molecules are cross-linked, the use of this method is limited (Yang and Shu, 2014).” (Schmidt, et al., 2016)
“Acid hydrolysis can be performed by using organic acids such as acetic acid, citric acid and lactic acid, and inorganic acids such as hydrochloric acid. However, organic acids are more efficient than inorganic acids (Skierka and Sadowska, 2007; Wang et al., 2008). Organic acids are capable of solubilizing non-crosslinked collagens and also of breaking some of the inter-strand cross-links in collagen, which leads to a higher solubility of collagen during the extraction process (Liu et al., 2015). Therefore, acidic solutions, especially acetic acid, are commonly used to extract collagen.” (Schmidt, et al., 2016)
“For the extraction of acid-soluble collagen, the pre-treated material is added to the acid solution, usually 0.5 M acetic acid, and maintained for 24 to 72 hours under constant stirring at 4°C, depending on the raw material (Wang et al., 2014; Nagai et al., 2015; Kaewdang et al., 2014).” (Schmidt, et al., 2016)
“After the extraction stage, a filtering is performed to separate the supernatant (residue) from the collagen, which is in the liquid phase. To obtain collagen powder, the filtrate is usually subjected to precipitation with NaCl. The precipitate is then collected by centrifugation and subsequently redissolved in a minimum volume of 0.5 M acetic acid and then dialyzed in 0.1 acetic acid for 2 days, and distilled water for 2 days, with replacement of the solution on average every 12 hours.” (Schmidt, et al., 2016)
“Moraes and Cunha (2013) analyzed collagen from the inner layer of bovine hide that was extracted under different temperature conditions (50, 60 or 80°C) and pH (3, 5, 7 or 10) under stirring for 6 hours. The hydrolysates that were produced in different conditions showed distinct properties. The highest levels of soluble proteins were obtained from treatments at a temperature of 80°C and a pH below the isoelectric point. The products obtained in conditions of extreme pH (3 and 10) or high temperatures (60 and 80°C) were completely denatured. The extractions with acidic pH and high temperature produced collagen with reduced molar mass. In general, the hydrolysates obtained with acidic pH formed firmer gels. The water retention capacity of the gels was approximately 100%, except for the hydrolysates that were obtained at high pH (7 and 10) and above the denaturation temperature (80°C).” (Schmidt, et al., 2016)
“Wang et al. (2008) optimized the conditions for extraction of acid-soluble collagen in skin from grass carp (Ctenopharyngodon Idella), having evaluated the effects of the concentration of acetic acid (0.3, 0.5 and 0.8 M), temperature (10, 20 and 30°C) and extraction time (12, 24 and 36 hours). The three tested variables showed a significant effect on collagen extraction and a positive relationship was found between time and the collagen yield. Increased temperature and concentration of acetic acid increased the yield to a certain value, which then decreased. The optimal conditions to obtain the highest yield of acid-soluble collagen in skin from grass carp were: an acetic acid concentration of 0.54 M at a temperature of 24.7°C for 32.1 hours.” (Schmidt, et al., 2016)
“Acid-soluble collagen from the skin and swim bladder of barramundi (Lates calcarifer) was extracted by Sinthusamran et al. (2013). The pretreated raw materials were extracted with 0.5 M acetic acid for 48 hours at 4°C. The acid-soluble collagen from the swim bladder showed a higher yield (28.5%) compared to that which was obtained from the skin (15.8%). In both cases, the collagen was identified as type I, with some differences in the primary structure. Both the skin and the swim bladder of barramundi showed potential for collagen extraction.” (Schmidt, et al., 2016)
“In general, chemical hydrolysis processes seek optimum conditions for obtaining higher yields by controlling process variables such as concentration, pH, temperature, and process time.” (Schmidt, et al., 2016)
Additional Notes on Salt-Extracted Collagen
Fisherman adds the following notes on salt extracted collagen. “Various buffers have been used to obtain salt-extracted collagen. Highberger et al. (1951) used an alkaline disodium phosphate buffer. Using isotopes Harkness et al., (1954) was able to determine that this fraction was a precursor to insoluble collagen. Jackson and Fessler (1955) and Gross et al. (1955) soon discovered that neutral salt probably extracts the same collagen as does the alkaline buffer and that both represent the most resent formed collagen. Increased amounts of collagen have been solubilized by increasing the concentration of NaCl. Perhaps no more than 10% of the total collagen can be extracted with salt, and generally much less than this is extractable. Less collagen can be extracted from skins of aged animals than from young animals and less is extracted from tendons than from skin. An amount of 0.5M NaCl in 0.5M tris buffer, pH 7.5 at 4 deg C for 2 – 4 days is currently used in this laboratory to obtain salt-extracted collagen. (Fishman (Ed), 1970)
Additional Notes on Acid Extracted Collagen
Fisherman adds the following notes on acid extracted collagen. “After collagen-containing tissue has been extracted with salt solutions additional collagen can be extracted by employing cold weak acids. Under the best of conditions, as much as 20% of of the total collagen may be extracted with cold acids. Ground-up tissue containing collagen may be placed directly in cold acids (after thorough washing with water) for extraction of soluble collagen without an intermediate salt extraction. In other words, weak acids will extract both the acid and salt soluble fractions. 0.5 M acetic acid is generally used in our laboratory to obtain acid soluble-collagen (Piez et al. 1961). Other acids have been advocated for example 0.1M citric acid and 0.1M sodium citrate pH4.3 (Gallop, 1955) 0.5M dihydrogen phosphate (Dumitru and Garrett, 1957) and 0.15M citrate buffer pH 3.8 (Mazurov and Orekhovich, 1959). The amount of collagen obtained varies with several factors including the pH of the acid (more being extracted at low pH), the age of the animal (more being extracted from younger animals) and the type of collagen-containing tissue (more is being extracted from skin than from tendons).” (Fishman (Ed), 1970)
“For the extraction of collagen by enzymatic hydrolysis, the raw material, which can be the residue of acidic extraction, is added to 0.5 M acetic acid solution containing selected enzymes such as pepsin, Alcalase® and Flavourzyme® (Novozymes®, Araucária PR, Brazil). The mixture is continuously stirred for about 48 hours at 4°C followed by filtration (Li et al., 2009; Li et al., 2013; Wang et al., 2014). The filtrate is subjected to precipitation and dialysis under the same conditions as for obtaining acid-soluble collagen.” (Schmidt, et al., 2016)
“Woo et al. (2008) optimized the extraction of collagen from the skin of yellowfin tuna (Thunnus albacares). Pre-treatment was performed with NaOH (0.5 to 1.3 N) at 9°C for 12 to 36 hours for the removal of non-collagenous protein. Subsequently, digestion with pepsin (0.6 to 1.4% (w/v) was performed in hydrochloric acid (HCl) solution (pH 2.0) at 9°C for 12 to 36 hours. The optimal extraction conditions were obtained with a pre-treatment of 0.92 N NaOH for 24 hours and digestion with pepsin at a concentration of 0.98% (w/v) for 23.5 hours.” (Schmidt, et al., 2016)
“Wang et al. (2014) isolated and characterized collagen from the skin of Japanese sturgeon (Acipenser schrenckii) using NaCl, acetic acid and pepsin for extraction. Initially, the skin was pretreated with NaCl and Tris-HCI and then the saline soluble collagen was extracted (SSC) in 0.45 M NaCl at pH 7.5 for 24 h with continuous stirring; this was performed six times. After the extraction with salt, the residue was suspended in 0.5 M acetic acid for the extraction of acid-soluble collagen (ASC); the procedure was carried out for 24 hours, twice. The material that was insoluble in acetic acid was used to extract pepsin-solubilized collagen (PSC) by using 0.1% (w/v) pepsin in 0.01 M HCl for 48 hours. The yields of SSC, ASC and PSC were 4.55%, 37.42% and 52.80%, respectively. All the isolated collagens maintained a triple helix structure and were mainly type 1 collagen, with similar morphology and amino acid profiles. The spectroscopic analysis in the midinfrared region using Fourier transform spectroscopy (FTIR) showed more hydrogen bonds in the PSC and more intermolecular cross-linking in the ASC. The different collagens also showed some differences in terms of thermal stability, which could have been due to the hydration level, as well as the number and type of covalent cross-links.” (Schmidt, et al., 2016)
“Kittiphattanabawon et al. (2010) extracted collagen from the cartilage of brown-banded shark (Chiloscyllium punctatum) and blacktip shark (Carcharhinus limbatus). Pre-treatment was performed using NaOH and ethylenediamine tetraacetic acid (EDTA). The extraction was initially performed with acetic acid for 48 hours at 4°C. Thereafter, the residue that was not dissolved by the acidic extraction was extracted with porcine pepsin in acetic acid for 48 hours at 4°C. The collagen extracted by pepsin had a much higher yield than the acid-extracted collagen. Furthermore, the spectra of both collagens that were obtained by FTIR were very similar; suggesting that hydrolysis with pepsin does not affect the secondary structure of collagen, especially the triple helix structure.” (Schmidt, et al., 2016)
“The method of extraction can influence the length of the polypeptide chains and the functional properties of collagen, such as viscosity, solubility, as well as water retention and emulsification capacity. This varies according to the processing parameters (enzyme, temperature, time and pH), the pretreatment, method of storage and the properties of the initial raw material (Karim and Bhat, 2009).” (Schmidt, et al., 2016)
“Thus it is necessary to perform a partially controlled hydrolysis of the cross-linked bonds and the peptide bonds of the original structure of the collagen in order to obtain the ideal distribution of molar mass for a given application (Schreiber and Gareis, 2007). This factor has emphasized the use of selected animal or vegetable proteolytic enzymes, such as trypsin, chymotrypsin, pepsin, pronase, alcalase, collagenases, bromelain and papain (GómezGuillén et al., 2011; Khan et al., 2011) because these permit the control of the degree of cleavage of the substrate protein. In addition, enzymatic hydrolysis presents some advantages compared with chemical hydrolysis, such as specificity, the control of the degree of hydrolysis, moderate conditions of action, and lower salt content in the final hydrolysate. Furthermore, enzymes can be generally employed at very low concentrations and it is not necessary to remove them from the medium (Zavareze et al., 2009). Despite the high cost of enzymatic hydrolysis, the fact that it results in lower levels of waste, better control of the process and higher yield justifies the use of enzymes.” (Schmidt, et al., 2016)
The use of ultrasound in the collagen extraction process
“Ultrasound is widely used to improve the transfer of mass by wet processes, which are of importance in terms of mixture, extraction and drying (Li et al., 2009). Ultrasound has been used successfully in collagen extraction by reducing the processing time and increasing the yield (Kim et al., 2012; Kim et al., 2013; Ran and Wang, 2014; Tu et al., 2015).” (Schmidt, et al., 2016)
“Ultrasound is a process that uses the energy of sound waves which are generated at a higher frequency than the hearing capacity of human beings (higher than 16 kHz) (Chemat and Khan, 2011). The effects of ultrasound in liquid systems are mainly due to the phenomenon known as cavitation (Hu et al., 2013). During sonication, cavitation bubbles are quickly formed, which then suffer a violent collapse, resulting in extreme temperatures and pressures. This leads to turbulence and shearing in the cavitation zone (Chemat and Khan, 2011).” (Schmidt, et al., 2016)
“In a study by Kim et al. (2012), the extraction of acid-soluble collagen from the skin of Japanese sea bass (Lateolabrax japonicus) showed increased yield and reduced extraction time after ultrasonic treatment at a frequency of 20 kHz in 0.5 M acetic acid. Extraction with ultrasound did not alter the major components of the collagen, more specifically the α1, α2 and β chains.” (Schmidt, et al., 2016)
“Ran and Wang (2014) compared the extraction of collagen from bovine tendon with and without the use of ultrasound (20 kHz pulsed 20/20 seconds). Conventional extraction was performed with pepsin (50 Umg-1 of sample) in acetic acid for 48 hours. For the extraction with ultrasound the same conditions were used, but the times of extraction with ultrasound (3 to 24 h) and pepsin (24 to 45 hours) were varied, resulting in a total of 48 hours of treatment. The combination of ultrasound with pepsin resulted in a greater efficiency of collagen extraction, reaching a yield of 6.2%, when the conventional extraction yield was 2.4%. The adequate time for extraction using ultrasonic treatment was 18 h. The collagen that was extracted from bovine tendon showed a continuous helical structure, as well as good solubility and fairly high thermal stability. The use of ultrasound in conjunction with pepsin improved the efficiency of the extraction of natural collagen without damaging the quality of the resulting collagen.” (Schmidt, et al., 2016)
“Li et al. (2009) utilized ultrasound (40 kHz, 120 W) to extract collagen from bovine tendon using the enzyme pepsin. The results showed that ultrasound increased extraction by up to 124% and reduced the process time. These results were explained by the increased activity and dissolution of the substrate because irradiation allows for a greater dispersion of pepsin and opening of collagen fibrils, which facilitates the action of the enzyme. The use of circular dichroism analysis, atomic force microscopy and FTIR showed that the triple helix structure of the collagen remained intact, even after the ultrasonic treatment.” (Schmidt, et al., 2016)
“According to Kim et al. (2013) the use of ultrasound in the extraction of collagen generated a higher rate of yield than the conventional extraction method with 0.5 M acetic acid, even when using a low concentration of acid (0.01 M). In addition, the yield of collagen from the skin of Japanese sea bass (Lateolabrax japonicus) increased greatly with increased treatment time and amplitude of ultrasound.” (Schmidt, et al., 2016)
“However, studies of the effect of ultrasound on enzyme activity are still very limited (Li et al., 2009; Yu et al., 2014). Yu et al. (2014) suggested that the activity of the enzymes papain and pepsin can be modified by ultrasound treatment, mainly due to changes in their secondary and tertiary structures. The activity of papain was inhibited, and the activity of pepsin was activated by the ultrasound treatment that was tested.” (Schmidt, et al., 2016)
“The application of ultrasound for a long period of time may give rise to elevated temperatures and shear strength, as well as high pressures within the medium because of cavitation. It can also break the hydrogen bonds and van der Waals forces in polypeptide chains, leading to the denaturation of the protein/ enzyme (Ran and Wang 2014).” (Schmidt, et al., 2016)
Inclusion Rate of Collagen in Sausages
Notes from Wenther (2003):
Henrickson (1980) – beef hide protein, collagen, is a useful extender, moisturizer, texturizer, or emulsifer in different food systems.
Bailey and Light (1988) – Non-detrimental effects to coarse-ground sausages were observed with levels up to 30 percent of collagen from the corium layer of hides.
Wiley and others (1979) – as a “rule of thumb,” use of high collagen meats should be limited to 15 percent of the meat block.
Rust (1987) – collagen should be limited to 25 percent of the total protein content in a sausage.
Millier and Wagner (1985) – an addition of rind and sinew should be limited to 5 percent of frankfurters to prevent undesirable sensory characteristics.
-Beef Tripe “Randall and others (1976) replaced the beef component in a meat emulsion system up to 80 percent with frozen honeycomb beef tripe. There were minimal changes in cooked yields at the 20 percent replacement level, but at 40 percent, the tripe caused adverse yield results. Drip losses paralleled the cooked yield results and at the 60 and 80 percent replacement levels, measurable lipid losses occurred with the tripe. Due to the nature of tripe (connective tissue protein), reduced-fat and water binding occurred by replacing the salt-soluble muscle protein. Firmness decreased at the 60 and 80 percent replacement levels and cohesiveness decreased at all replacement levels.” (Wenther, 2003)
“Jones and others (1982) conducted research in which beef tripe was used in 30 batches of bologna as a collagen source. Meat emulsions were prepared with five tripe levels (0, 10, 20, 30 and 40 percent of the formulation). Total collagen and insoluble collagen were significantly higher (P<0.05) for each increasing tripe level. Only minor differences were observed in the soluble collagen fractions. In comparison to lower tripe levels, the 40 percent tripe level had a lower smokehouse yield (P<0.05). The authors also concluded that the higher the collagen content in the formulation leads to a more “brittle” emulsion which was determined by lower hardness and chewiness scores. Furthermore, the authors reported decreased firmness and bind values in the cooked product and decreased visoelastic properties. In the raw batter in formulations that contained tripe levels greater than 10 percent.” (Wenther, 2003)
–Tendons from Beef Hind Leg Muscles “Sadler and Young (1993) replaced a portion of the lean in a conventional emulsion formulation with tendon from beef hind leg musdes. The tendons were homogenized and used either in a raw state or a preheated state. In the preheated treatment, the homogenized tendon was subjected to four temperature ranges (50, 60 70, 80 °C). In the first study, all treatments were observed by replacing 20 percent of the meat protein with 20 percent tendons (all treatments). Hardness doubled by replacement with raw tendon or tendon heated at 50 °C, but returned to approximately no-replacement levels at temperatures higher than 50 °C.” (Wenther, 2003)
“In the second study by Sadler and Young (1993), a portion of the lean meat was replaced with 0, 5,10,15, 20 or 25 percent tendon homogenate (raw and preheated at 70 °C). All attributes measured by the sensory evaluation decreased with increasing collagen content, but to a lesser extent with preheated tendon. By comparison of panel scores and texture profile analysis, it was determined that reduced fracturability was the texture parameter that panellists objected to when heated tendon replaced some of the lean. The authors concluded that a 60 °C preheated tendon homogenate at a 20 percent lean meat replacement can be effective for positive sensory attributes.” (Wenther, 2003)
–Desinewed Connective Tissue “Desinewed connective tissue has been obtained from cow meat and beef hind shank meat and utilized by many authors. Ladwig and others (1989) added two levels of collagen to meat emulsions to determine the effect of muscle collagen on emulsion stability. The authors revealed that adding additional collagen to meat emulsions shortened the total chopping time and decreased emulsion stability, but had no effect on protein solubility.” (Wenther, 2003)
“Eilert and Mandigo (1993), Eilert and others (1996ab), and Calhoun and others (1996ab) performed extensive research with desinewed connective tissue from beef hind shank meat. Eilert and Mandigo (1993) noted that thermal processing yield losses declined with increased modified connective tissue level (0, 10, 20, 30, 40 percent) and hypothesized that the addition of modified connective tissue may be effective for reducing processing yield losses in low-fat meat systems.” (Wenther, 2003)
“Eilert and others (1996ab) and Calhoun and others (1996ab) studied the relationship between phosphates and desinewed beef connective tissue. Collagen solubility was maximized with a 3.5 percent acidic phosphate solution, while hydration was optimized with a 3.5 percent alkaline phosphate solution (Eilert and others 1996a). The authors concluded that exposing connective tissue to high concentrations of phosphate will dramatically alter binding and solubility.” (Wenther, 2003)
“Calhoun and others (1996ab) expanded on the previous research with studies of preblending connective tissue with phosphates. While Calhoun and others (1996a) revealed that preblending sodium add pyrophosphate with modified beef connective tissue and subsequent addition of alkaline phosphate created a modified connective tissue product similar to the control product, Calhoun and others (1996b) determined that preblending modified connective tissue and sodium tripolyphosphate was not beneficial.” (Wenther, 2003)
“Osbum and other (1999) determined that the incorporation of desinewed beef connective tissue gels in reduced-fat bologna decreased (P<0.05) product hardness and increased juiciness, which indicated potential for the utilization of beef connective tissue gels as water-binders and texture-modlfiylng agents in reduced-fat comminuted meat products.” (Wenther, 2003)
–Beef Hide (Skin) “Although hamburger is not considered a processed product, hamburger is an intermediate particle-size product (Whiting 1989) and defined In the Code of Federal Regulations with section 319.15b (USDA 2002a) as: “Chopped fresh and/or frozen beef, with or without added beef fat and /or seasonings. Shall not contain more than 30 percent fat, and shall not contain added water, binders or extenders. Beef cheek meat may be used up to 25 percent of the meat formulation.” Chavez and others (1985) added bovine hide collagen as an extender to ground beef replacing lean meat at a level of 0, 10, or 20 percent. Beef patties with the collagen were found to be superior (P<0.05) in juiciness by the taste panel, while the flavor, texture, and overall acceptability decreased as the collagen level increased.” (Wenther, 2003)
“Asghar and Henrickson (1982) investigated the effect of the addition of food-grade bovine collagen at 10, 20, and 30 percent levels on other protein fractions in bologna. The authors revealed that the solubility of sarcoplasmic and myofibrillar proteins decreased, while percent solubility of collagen increased with increasing level of added hide collagen. Rao and Henrickson (1983) replaced 20 percent of the lean meat component in bologna with 20 percent beef hide collagen. The replacement did not alter the functional characters such as raw bologna emulsion stability and pH, cook yield, pH, water activity, and expressible moisture in the cooked bologna. The bologna with collagen had increased (P<0.05) shear force values compared to bologna with no collagen.” (Wenther, 2003)
–Pork Skin “Satterlee and others (1973) produced pork skin hydrolyzates and replaced non-fat dry milk in a sausage formulation. The utilization of pork skin hydrolzates produced sausage with a slightly better water and fat holding ability even though the emulsion capacity was slightly lower than the capacity of non-fat dry milk emulsions.” (Wenther, 2003)
“Sadowska and others (1980) and Sadowska (1987) utilized varying levels (5, 15, 20, or 25 percent) of raw and cooked (100 °C for 0-90 minutes) pork skin collagen to examine the rheological properties of sausage batters and cooked sausage, respectively. It was reported that replacing 20 percent of the meat protein with pork skin collagen decreased batter viscosity and cooked sausage elasticity. Incorporation of cooked skin (15 percent of the total protein) resulted in batter with higher viscosity and higher cooked sausage elasticity when compared to batter or cooked sausage not containing pork skin collagen. The authors concluded that the addition of greater than 2.5 percent pork skin collagen would result in altered cooked sausage texture and appearance. Puolanne and Ruusunen (1981) hypothesized that connective tissue may be important for the water binding capacity and firmness of cold sausage.” (Wenther, 2003)
Quint and others (1987) produced a loaf product that contained flaked pork skin and water that was pre-emulsified by passing it through an emulsion mill. The authors determined that the incorporation of the pre-emulsion improved bind of the emulsion and increased firmness, redness (a value), and yellowness (b value) colors of the loaf product. Delmore and Mandigo (1994) also used flaked pork skin sinew to low-fat, high-water added frankfurters at varying levels (0, 10, 20 percent of the formulation). Cooking yield, texture, and purge of the frankfurters were not altered by replacement levels of up to 20 percent pork connective tissue. There was no difference in juiciness, favor, texture, or overall acceptability detected by consumer sensory panelists between frankfurters containing 0 to 10 percent pork sinew. Fojtik (1997) incorporated flaked pork skin at levels of 10 and 20 percent into fresh pork sausage. The author reported that consumer panelists ranked lowfat sausage patties containing 10 percent pork skin higher for flavor, juiciness and overall acceptability than patties containing higher fat levels or pork skin levels. Fojtik concluded that the patties that contained 10 percent pork skin were more tender than those containing 20 percent pork skin (Fojtik 1997).” (Wenther, 2003)
Osbum and others (1997) produced gels from flaked pork skin with varying amounts of added water (100, 200, 300, 400, 500, 600 percent). These pork skin gels were utilized in reduced-fat bologna at levels of 10-30 percent addition. The greatest purge for any bologna occurred with the 600 percent added water, 30 percent addition treatment. Taste panel analysis revealed that juiciness scores increased as added water and percent gel addition increased. The overall acceptability of the pork connective tissue bologna tended to increase as added gel and added water increased. The authors summarized that the incorporation of pork connective tissue gels varied the functional, textural, and sensory attributes in reduced-fat bologna (Osbum and others 1997).” (Wenther, 2003)
“More recently, Prabhu and Doerscher (2000) utilized processed pork skin collagen in reduced-fat frankfurters to increase cooking yield and decrease purge in the final product. The authors also researched the effect of pork collagen in fat-free pork sausage formulations. The results indicated increased cooked yields with a reduction in cooked diameter shrink. The authors concluded that the addition of 1 percent hydrated collagen at a 1:4 ratio is a cost-effective (e.g improved yields), functional ingredient that can improve the quality (e.g. texture improvement) of various meat products.” (Wenther, 2003)
“Hoogenkamp (2001) cited the use of pork skin (rinds) in the production of preemulsions, which are another method to incorporate this raw material into emulsified meats. Pork skins are pre-blanched for about 20 minutes at 80 °C to soften the collagen tissue. The pork skins are added into the chopper prior to the addition of fat and chopped to a fine particle size which allows an increase in the pre-emulsion ratio utilized in the formulation.” (Wenther, 2003)
“Researchers have studied the use of skin in raw or cooked form. Sadowska and others (1980) and Sadowska (1987) utilized varying levels (5, 15, 20, or 25 percent) of raw and cooked (100 °C for 0-90 minutes) pork skin collagen to examine the rheological properties of sausage batters and cooked sausage, respectively. It was reported that replacing 20 percent of the meat protein with pork skin collagen decreased batter viscosity and cooked sausage elasticity. Incorporation of cooked skin (15 percent of the total protein) resulted in batter with higher viscosity and higher cooked sausage elasticity when compared to batter or cooked sausage without pork skin collagen. The authors concluded that the addition of greater than 2.5 percent pork skin collagen would result in altered cooked sausage texture and appearance. Puolanne and Ruusunen (1981) hypothesized that connective tissue may be important for the water binding capacity and firmness of cold sausage.” (Wenther, 2003)
-Poultry / Turkey Skin “Poultry skin is also a source of collagen that may be used in comminuted meat systems. Campbell and Kenney (1994) listed poultry skin as generally being a filler ingredient in poultry or mixed-species batter sausages. The authors described that poultry skin may be listed on ingredient labels as “poultry by-products” and in other products skin cannot be added in higher proportion than occurs naturally.” (Wenther, 2003)
“Due to its high collagen content, broiler skin meat possessed inferior emulsifying capacity (Maurer and Baker 1966). Moreover, Hudspeth and May (1969) analyzed skin, heart, and gizzard tissues of turkeys, hens, broilers, and ducklings for emulsifying capacity of salt-soluble protein. The authors reported that skin was the least desirable tissue in emulsification properties and was not as effective in emulsifying ability as muscle tissue from the same class of poultry.” (Wenther, 2003)
“On the other hand, Prabhu (2003) reported that functional collagen proteins from chicken and turkey skins can bind three to four times their weight in water and can form a firm elastic “cold” gel producing texture characteristics that are similar to meat. Prabhu stated that this gel functions as a matrix stabilizer of finely comminuted and coarse-ground meat products such as frankfurters or sausages. The author suggested that collagens immobilize free water and prevent moisture loss during heat processing as well as improve texture while reducing purge loss.” (Wenther, 2003)
Heat Modified Collagen
Notes from Tarté, R. (Ed) (2009).
“The functional properties of collagen can be modified collagen or collagen-rich raw material under different time/ temperature combinations some of which has been reported in the literature (eg 100deg for 30, 60 or 90 minutes; Sadowska et al; 1980) During processing of most processed meats native collagen generally melts and becomes gelatin too late in the process (i.e. at temperatures of between 75 and 80 deg C) to become part of the batters gel structure. Precooked collagen, on the other hand, solubilizes early during chopping and is, therefore, able to provide functionality to the meat batter. (Whiting, 1989) This was born out in a study that evaluated the effect of temperature on the water-binding ability of concentrated pork skin CT gels (Osburn, Mandogo, & Eskridge, 1997). Pork skin CT was first obtained by cutting pork skin into strips, followed by freezing, grinding, refreezing and flaking. It was then combined with varying amounts of water and heated at 50 deg C, 60, 70 and 80 deg for 30 minutes. Under these conditions, it was found that gels produced by heating to at least 70 deg C had the highest water-binding ability. After cooling, these 70 deg C gels were tested in reduced-fat (2%, 3.5%, 4,3%6.8% and 12% fat) bologna, resulting in decreased hardness and increased juiciness.”
See his notes on Enzyme Modified Collagen, p. 152.
Negatives of Using Collagen in Fine Emulsion Sausages
“The possibility in using collagen found in great abundance in beef hide has been discussed by Elias et al., 1970. They indicated that collagen fibres and granules could be isolated from beef hide and used as a possible binder extender in meat products. An early study has shown that collagen, the major protein of skin, bone and connective tissue was detrimental to the emulsifying capacity of poultry meat (Maurerand Baker, 1966). The inability of collagen to emulsify fat and its ability to convert to gelatin upon make it an undesirable ingredient in sausage formulations.” (Satterlee, et al., 1973)
“Another property of collagen its nutritional value should be discussed when collagen is to be considered as a food additive. Collagen is known to be deficient in the essential amino acid tryptophan and limiting in other essential amino acids such as lysine, threonine, and methionine. However, it has been shown (Ashley and Fisher, 1966) that chicks fed on a diet of 10% gelatin+ 3% casein had the body weight gains equal to those fed on a diet of 13% soy protein and 0.2% methionine. Erbersdobler, et al. (1970), using male rats as the experimental animal showed when collagen or gelatin was incorporated into the diet of levels of up to 5% of the total diet weight, there were slight improvements in daily gain and feed conversion. Therefore, collagen will not lower the nutritional quality, if used along with a balanced protein and maintained at a low level in the diet, such as would be the case when a collagen hydrolyzate is used as a binder or extender in meat emulsions.” (Satterlee, et al., 1973)
“Collagen in its native state is resistant to proteolytic action of most enzymes, but when heated the resultant gelation is easily enzyme degraded. Hydrolysis of a protein by means of an enzyme will also change the physical characteristic of the protein.” (Satterlee, et al., 1973)
Maurer and Baker (1966) found an inverse relationship between the collagen content in poultry meat and its emulsifying capability. They write that “the method used in this study provides comparative estimates of the capacity of individual parts of different classes of poultry to emulsify fat. It has been found that the collagen content of poultry meat is a reliable estimator of emulsifying capacity when dealing with meat and skin mixtures. Collagen can be detrimental to the process of making poultry meat emulsions because of the inability of collagen to dissolve and form stabilizing membranes necessary for emulsion formation. In general, the voluntary muscle meats such as breast and thigh have a higher emulsifying capacity than the gizzard, heart or skin of poultry meat. Light fowl total carcass was found to emulsify significantly less oil than any other class of poultry.”
The following graph illustrates their conclusions well.
That collagen on its own is not a silver bullet to cheaper or better sausage production is clear. That it has very interesting characteristics is equally clear. An understanding of the nature of collagen and the different techniques of manipulating it inform the meat processing professional in every respect. Understanding its limitations and potential is key before one begins test kitchen trails.
Munro, H. N., Allison, J. B. (Editors). 1964. Mammalian Protein Metabolism, 1st Edition, Volume I, eBook ISBN: 9781483272924, Academic Press, 1st January 1964
Schmidt, M. M., Dornelles, R. C. P., Mello, R. O., Kubota, E. H., Mazutti, M. A., Kempka, A. P. and Demiate, I. M.. 2016. Collagen extraction process. Mini Review. International Food Research Journal 23(3): 913-922 (2016) Journal homepage: http://www.ifrj.upm.edu.my
Tarté, R. (Ed). 2009. Ingredients in Meat Products: Properties, Functionality and Applications. Springer.
Wenther, J. B.. 2003. The effect of various protein ingredients utilized as a lean meat replacement in a model emulsion system and frankfurters. Iowa State University.
From Collagen Scaffolds for Orthopedic Regenerative Medicine, April 2011, JOM: the journal of the Minerals, Metals & Materials Society 63(4):66-73, DOI: 10.1007/s11837-011-0061-y. Gráinne Cunniffe and Fergal J. O’Brien
Notes on Proteins used in Fine Emulsion Sausages
by Eben van Tonder
24 May 2020
I am interested in understanding the ability of gel formation of different meat proteins, their water holding capacity and the relative protein content of various ingredients used in making fine emulsion sausages. This is important, especially in South Africa where there is a heavy reliance on MDM/ MRD in emulation sausages. What can be added to increase its water holding capacity and firmness and can a pure but economical sausage be produced?
Different Meat Related Classes of Products
In making sense of this approach, it is beneficial to understand that we deal with three classes of meat-related products. I call it the pure, the deceptive and the dishonest, thus revealing my personal bias. Pure Meat products which, in my use of the term, means products where every ingredient except the spices come from an animal carcass.
Meat Analogues are starches and soyas, grains and cereals which are made so that it tastes like meat, but contains no part of an animal carcass. This is the dishonest or hypocritical class of products. Why would a vegan, for example, who does not want to eat meat, buy a product disguised as meat, but which, in reality, contains no meat? Pure meat and meat analogues are therefore two opposing and extreme ends of the spectrum.
Meat Hybrids is the middle of the two and combines meat and plant-based protein, essentially for the purpose of achieving a cheaper product. I call it deceptive because the consumer is most often misled as to the real nature of the products they buy (I say this, despite the label declaration, which is often still enigmatic to consumers). They think it’s meat, but it contains a percentage of non-meat fillers. This is almost always done to reduce the price of the product, which, in a country like South Africa, is not necessarily a bad thing. Affordable food, where “affordable” is relative to the income level of the consumer, is a very important consideration. It must also be stated that for the most part, large producers of this kind of products do not add as fillers and extenders, anything except high quality, acceptable and healthy products such as soya in the meat to extend it.
My personal preference for pure meat products is mainly based on taste and, to a lesser extent, on matters such as allergy which relate to health in that some of the fillers may be allergens. Taste of pure meat products can, in my personal opinion, not be matched in taste, firmness, mouth feel, or any other organoleptic characteristics (the aspects of the end-product that create an individual experience via the senses—including taste, sight and smell).
I am therefore interested here to learn more about the functional value of various animal proteins and fats and fillers and extenders, customarily used in producing fine emulsion sausages.
The Cost of Protein
In evaluating the options for a producer, one must first understand the real cost of protein. In the table below, you can see the relative cost per kg of protein sources, expressed in South African Rand. The buying prices per kg obviously change and you can use the following spreadsheet to recalculate it with the current prices. More importantly than the cost of the protein source is the inclusion ratio of protein in the different sources and the real cost of the protein.
So, taking the prices above, skin was, at the time of writing, the cheapest protein source, followed by soy TVP, then soy isolates, followed by offal and then chicken MDM. For knack, you need collagen.
Starch is an interesting ingredient. Tapioca Starch contains 6.67% protein (66.7g per kg) (eatthismuch) At the writing of this article, it is R12.00 per kg, which is R179,91 per kg of protein making it more expensive than MDM, but at an inclusion rate of around 4%, and with soya isolate at R39.00 per kg
The convention in SA became to use the cheapest protein source available, which is normally seen as MDM/ MRM. Add soy for better binding and pork rind, made of collagen protein, for even greater binding and gel formation. (Mapanda et al., 2015) In reality, it is done to make the products cheaper for the consumer.
The Extremities of Formulating a Sausage
There are at least three sets of characteristics normally taken into account when formulating a sausage.
-> Total Meat Equivalent (TME)
In South Africa, the minimum Total Meat Equivalent (TME) for different classes of meat products is laid down in legislation. Let’s review briefly the important equations which will be applied to the table of possible ingredients with protein percentages above.
The Dutch chemist Gerard Mulder (1802–1880) had published a paper in a Dutch journal in 1838 and this was reprinted in 1839 in the Journal für praktische Chemie. Mulder had examined a series of nitrogen-rich organic compounds, including fibrin, egg albumin, gluten, etc., and had concluded that they all contained a basic nitrogenous component (~16%) to which he gave the name of “protein” (Munro and Allison, 1964) from a Greek term implying that it was the primary material of the animal kingdom.
The term protein was coined by Jöns Jacob Berzelius, and suggested it to Mulder, who was the first one to use it in a published article. (Bulletin des Sciences Physiques et Naturelles en Néerlande (1838); Hartley, Harold (1951) “Ueber die Zusammensetzung einiger thierischen Substanzen” 1839). Berzelius suggested the word to Mulder in a letter from Stockholm on 10 July 1838. (Vickery, H, B, 1950)
Total protein % can therefore be derived from an analysis of the nitrogen content of a meat product. The following equation is used and is derived from the fact that proteins contain around 16% nitrogen.
% N by analysis x 6.25 = % Protein (since 100/16 = 6.25)
An example is if nitrogen, by analysis, is 1.85%, then the % protein is 1.85 x 6.25 = 11.5% (protein).
The protein content in lean meat is also known to be around 21%. The factor to convert protein % to lean meat is therefore 100/21 = 4.8 if we take the lean meat as 100% and divide it by 21. So, in our example, 11.5% x 4.8 = 52.2% lean meat. The equation is:
% Protein x 4.8 = % lean
We can combine these two factors to give us a way to go from % nitrogen directly to the lean meat %. 6.25 x 4.8 = 30 and % N x 30 = % lean.
A good summary of the thinking early in the late 1800s and early 1900s on the subject exists in the South African Food, Drugs and Disinfectants Act No. 13 of 1929 (See note 1). As an important historical document, it sets out the determination of total meat content. It essentially remained unchanged (apart from minor updates).
The calculations of total meat content are defined in subparagraph 4 (iv) which reads as follows: “In all cases where it is necessary to calculate total meat under regulations 14 (1), (2), (3) and (4), the formula used shall be:—
Percentage Lean Meat = (Percentage Protein Nitrogen × 30 ). Percentage Total Meat = (Percentage Lean Meat + Percentage Fat).”
-> Water Holding Capacity (WHC)
Non-meat binders are often added to meat. Such binders and extenders commonly include flour, starch, breadcrumb, cereal binders, TVP and rusk. Often these are used to hold and bind large amounts of water to reduce product cost.
There are legal limits that must be adhered to in terms of protein content for a sausage to be called a meat sausage. When fillers and extenders are used such as these, it is, however, not a pure meat product, and hybrids are created which contains both plant and animal components.
Here there is a major misconception. All animal proteins have the ability to form gels and to hold water. The functional ability of various animal proteins to do this, however, differs significantly. A thorough knowledge of these abilities of various components of the carcass is required to determine which proteins will be best to achieve what result in any particular sausage formulation.
My suspicion is that these differences were discovered as soups and meat stews were developed by early humans, which was probably motivated by the desire to soften various parts of the carcass for consumption. There is evidence that a centre of these developments emerged on the Russian Steppe. It is interesting that Russia also became the world leader in fine emulsion meat technology and the creation of hybrid meat products.
-> Taste and Texture
Taste and texture differ considerably between pure meat products and hybrids, which leads to my personal preference of the former. The meat industry employs spices as one of the major resources of making hybrid products more “acceptable”.
Animal Protein and Gel Formation
There are three functional characteristics of meat, important to our study, namely gelation, emulsification and water holding ability. It relates to meat particle binding and adhesion ability. Processed foods are the result of the combination of several protein functionalities. In mathematics we will represent it with a polynomial function. An example of this is a Russian sausage with its firm texture and juiciness which is the result of a composite protein network system which in turn is created by protein-protein interaction (gelation), protein-fat interaction or fat encapsulation (emulsification) and protein-water interaction (water binding). Even a slight change in ingredient composition and processing conditions are enough to alter the final texture materially. (Yada, 2004)
Yada (2004) summarises the functional properties of muscle proteins as follows:
Yada (2004) defines gelation as “viscoelastic entity comprised of strands or chains cross-linked into a continuous network structure capable of immobilizing a large amount of water. The process of forming a gel, i.e. gelation, occurs in muscle foods as a result of unfolding and subsequent association of extracted proteins, usually in the presence of salt and sometimes also phosphates. The rate of structural change, i.e. denaturation, is critically important. A slow unfolding process, which typically occurs with a mild heating condition, allows polypeptides to align in an ordered manner into a cohesive structured network capable of holding both indigenous and extraneous water.” (Yada, 2004) When producing boneless hams, the gel formed at the junction of the meat chunks is responsible for the adhesion and is responsible for the integrity of the product.
Cheapest Meat Product: Structure and Characteristics
The key ingredient used in South Africa in producing fine emulsion sausages is MDM/ MRM. It is the cheapest meat product, most often used as the basis for meat hybrids. (see MDM – Not all are created equal!) MDM is a source of meat protein which is “complete, containing all the nine essential amino acids.” (Mapanda et al., 2015) MDM is, however, mostly compromised due to the way it is manufactured. It also contains the least amount of protein on our table of proteins containing raw materials listed above. The proteins and fibres are denatured / damaged to such anextent that even the protein that it contains is retarded in terms of its ability to form a gel and hold water. Non-meat extenders, fillers and emulsifiers are, therefore, often used to compensate for this. Such plant products often include soy isolate and soy concentrate. Animal products are also often used such as milk powder, whey powder and egg white. Pork skinor rind emulations provide firmness. Fillers are usually carbohydrate materials such as carrageenan and various starch materials (Mapanda et al., 2015) depending on the price point that the formulator is targeting. Low cost sausages can contain as much as 15% such fillers and extenders.
In the Mapanda study, polony was considered as an emulation type sausage. “Polony is formed by changing coarse heterogeneous meat into a homogeneous meat mass consisting of dispersed water, fat and protein, which during heating is transformed into a gel. Polony is regarded as a fully cooked emulsified sausage product” (Mapanda et al., 2015).
Skins or skin emulsions are added to provide firmness and knack, but soya and starch are customarily added to reduce the cost. Inspired by trends from Russia, there has been a trend from around 1946 (following World War 2) in the USA to employ various serials and starches in meat processing as a way to extend the meat. As such, soy protein has been commonly used. Large manufacturers of soy products aggressively targeted the meat industry to continue the use of soy as a meat extender. Spice companies became the preferred method of distribution and large amounts of money was spent on developing recipes that would include soy and starch. The industry preached that this inclusion was “beneficial” from an economic perspective and is healthy. They proclaim that soy is a good “replacer of meat due to its essential amino acids, whose composition (though slightly lower in quantity) is no different from that of meat.” Functionally, they pointed to the fact that soy functions as a binder of fine emulsion type sausages such as polony where it contributes to the water holding capacity and the emulsification of fat in the gel. The real benefit is that it’s cheaper and easier to work than meat, and by itself, this argument is without question a valid one.
POLONY: An Example of a Meat Hybrid
Let’s now look in greater detail at how different fillers, emulsifiers and extenders are used along with MDM to create a low cost meat hybrid. We follow work done by Mapanda, et al. (2015) where they investigated “varying quantities of chicken mechanically recovered meat (MRM), soy flour (S) and pork rind (R)” were used to manufacture South African polony. For the full article, see Effect of Pork Rind and Soy Protein on Polony Sensory Attributes.
Preparation of Meat
In the Mapanda study (2015) the meat components were prepared as follows.
Rind Emulation: “Pork rind is quite tough in texture. To soften it, it was precooked before use. 7.5 kg of rind was cooked in 7.5 kg (litres) of water. The cooking time varied from 4 to 5 h for the three batches of pork rind prepared. After cooking, the pork rind and water mixture was re-weighed and water added to make up the 15 kg before chopping the mixture in the bowl cutter until a fine, sticky homogenous mass called rind emulsion was formed. The rind emulsion was then allowed to cool to room temperature prior to weighing and vacuum packaging. The rind emulsion was subsequently stored at -18°C until chemically analysed or used in polony processing.” (Mapanda et al., 2015)
MDM/ MRM: “The only preparation done on the frozen MRM involved cutting it into smaller blocks for the purpose of easily fitting into the bowl cutter. The cut blocks of MRM were vacuum sealed and frozen until polony processing commenced.” (Mapanda et al., 2015)
Sausage Formulation and Analysis
In the Mapanda study (2015) the meat components were blended as follows with the following functionals added, resulting in the analysis as given.
“All nine treatments were formulated to contain 10% protein (equivalent to 48% LME). MRM, soy flour and pork rind all vary in quantities to maintain a 10% protein in the respective treatments. The percentage of water added also varied to maintain a constant product weight, while the percentage of additives was kept constant. Additives added were 8% tapioca starch, 1.8% salt, 0.016% nitrite, 0.3% phosphate, 0.05% ascorbic acid, 0.02% erythrosine dye, 0.1% each for black pepper and cayenne pepper, 0.03% ginger, 0.2% garlic, and 0.05% each for nutmeg and coriander. Each polony sample was designed to weigh 1.5 kg. Since 10 polony units were produced for each treatment, the total mixture of polony emulsion (meat and all ingredients added for emulsification in a bowl cutter) was 15 kg. ” (Mapanda et al., 2015)
“Order of adding the ingredients was the same, i.e. ingredients were added when the bowl cutter was running at low speed. After that, the speed was increased for the final chopping phase. The MRM was added and chopped first, followed by adding the salt, nitrite, the phosphate and one third of the water. This was followed by adding the rind emulsion. After that, soy flour was added into the bowl cutter and chopped for 2 min before adding spices and another third of the water. The tapioca starch was then added, after which the ascorbic acid and the last third of the water was added.” (Mapanda et al., 2015)
“The end temperatures after chopping the polony emulsion varied between 12°C
and 17°C.” (Mapanda et al., 2015)
“The polonies were cooked in a steam bath for about 2 h to an internal temperature
of 80°C as measured by a thermocouple. The cooked polony was then cooled in clean running water prior to storage at 4°C until chemical, instrumental and sensory analyses were done on the respective samples.” (Mapanda et al., 2015)
Effect on Colour
“The redness decreased, in the Mapanda study (2015), “with an increase in both rind and soy proteins. Chicken MRM contains red pigments of blood (myoglobin and haemoglobin). The replacement of MRM with white proteins (rind and soy) reduced the red colour of the polony treatments.” (Mapanda et al., 2015)
“The present findings for pink colour are consistent with Abiola and Adegbaju, who reported that, when pork back fat was replaced with rind levels of 0, 33, 66 and 100%, the colour of pork sausages decreased correspondingly. The negative effect of MRM replacement with rind and soy on the pink colour of polony can be counteracted by adding more dye during the emulsification stage. In South Africa, dyes such as erythrosine BS can be added to enhance the pink colour of polony up to the maximum level of 30 mg/ kg of the product, Department of Health.” (Mapanda et al., 2015)
“In the treatments where rind was added, white spots were observed. The white spots were actual pieces of rind which resulted from incomplete emulsification of the pork rind emulsion by the bowl cutter. This negative attribute could be rectified by extensive chopping of the raw batter of the treatments containing pork rind.” (Mapanda et al., 2015)
“The replacement of MRM with rind levels of up to 8% and soy levels of up to 4% increased the hardness (firmness) of the polony treatments, while treatments with 8% soy were softer at all levels of rind. Similar results were obtained for gumminess (Figure 5). These results show that good quality polony with acceptable hardness can be obtained with up to 4% soy and 8% rind. Beyond 4% of soy flour, the products become softer and sticky. According to Chambers and Bowers, hardness is the most important attribute to consumers because it determines the commercial value of the processed meat products. Approximately 60% of consumers will be willing to buy a sausage with a hardness of 47.3 N and higher (Dingstad). However, higher values for the parameter do not necessarily mean better quality. There is a cut-off point above which the texture of comminuted meat products would be unacceptable.” (Mapanda et al., 2015)
Related to cohesiveness, the Mapanda (2015) study found that “the addition of binding aids such as soy and rind improves cohesiveness, as long as too much is not used (Trock). Chin  established that the use of incremental levels of soy protein below 3% decreased the cohesiveness of low-fat meat products. The current results disagree with the findings of Chin as some of the treatments of polony in which only soy protein was used, for instance at the level of 4%, showed that cohesiveness increased. A possible explanation might be the difference in the fat content of the products used in their study and in the current study.” (Mapanda et al., 2015)
“For sensory texture, the attributes analysed were firmness, pastiness and fatty mouth feel. All treatments decreased in sensory firmness due to an increase of soy and rind proteins. For both pastiness and fatty mouth feel, the mean scores for these two texture attributes increased in all samples compared to that of the control treatment. Feiner highlighted that the replacing of lean meat with soy protein and water, as was done in the present study, affects texture and firmness because the replaced meat proteins contribute positively to the named parameters. It can clearly be seen that an increased replacement of chicken MRM with pork rind and soy flour reduced firmness and increased the sensory textural attributes of pastiness and fatty mouth feel in all the polony treatments, except for the control sample.” (Mapanda et al., 2015)
Pure Meat Products at the Same Low Cost
The question now comes up, if a pure meat product can be produced at the same low cost as is done in the Mapanda study. The Yada (2004) study and the table of various functional values of different animal proteins is the first clue.
I again present this article as a “work in progress” study, as I did with other investigations. Results will be reported on unless a proprietary benefit can be derived. Any suggestions and comments can be mailed to me at email@example.com. All results of relevant investigations will be listed below and the controlling principle will be: “Why think, if we can test?” I embark on this voyage with great excitement!