MDM – Not all are created equal!

MDM – Not all are created equal!
By Eben van Tonder
16 April 2018

Frankfurters

Introduction

Last Saturday I turned 50.  I did three things that I insanely enjoy.  One was to spend time with a meat and business legend.  Over the years I have researched and got to know many such men.  Those who are still alive, I got to know personally.  Those who passed away, I studied their lives.  Jacobus Combrink who created arguably the most successful butchery in South Africa in the 1800s;  David de Villiers Graaff, his protege and the man who took Combrink & Co. and turned it into the Imperial Cold Storage and Supply Company Ltd. (ICS) which in turn merged into the food conglomerate Tiger Brands with the Combrink & Co part of the operation being assimilated into the Enterprise/ Renown merger;  JW Moore who set up the Eskort curing operation under his Farmers Cooperative Bacon Curing Company in Estcourt, Natal.  Further afield there is the three Harris’s.  Nick Harris, whom I have the privilege to know, was key in the creation of the New Zealand curing operation, Hellers.  Together with his brother, Bryan, they currently own an abattoir, deboning and processing plant in Cheviot where they grow up and where Nick owns large farmland.  From the previous century, the brothers George and Thomas Harris from Calne in Wiltshire who created C & T Harris, arguably the most successful bacon operation in British history.  From Australia, Wright Harris and his Castlemaine Bacon Company who fought in the second Anglo-Boer war in South Africa.  Interestingly enough, none of the Harris’s from New Zealand, Australia or England are related.  From the USA there is the legendary Philip Armour and his Armour Packing Plant in Chicago who was, according to my research, closely linked with the direct addition of nitrites in curing brines. His company is one of the reasons why anti-trust laws exist in the USA.  For my 50th birthday, I was on the farm of Etienne Lotter.

Etienne stands shoulder to shoulder with any one of these formidable men. It fascinates me that all these men share an unwavering focus, the ability to make quick and good decisions, resolve of steel, passion, commitment, and an obsession to invest in people.  A story is told of Phil Armour that he showed his packing plant to visitors one Sunday.  Ford got his idea about assembly lines from Phil and it was indeed something to behold.  A newspaper reporter tells the story that they were walking back from the factory and could see the church where many of the men who worked for him attended adult education after church.  He reportedly pointed to his packing plant and said, “there we make bacon” and then to the church and said, “and there we make men!” He liberally invested in people and he himself claimed that he never fired someone.  That is not to say that it was easy to work for him as is or was true of all these men.

The second thing I did which I insanely love was to hike up the Magaliesburg on Etienne’s farm, Eswitch Stud Farm.  There was no clear footpath up and it made for an adventure through the thick grass, trees, and ferns.

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The 3rd thing was talking meat curing with Etienne the entire Saturday and Sunday morning!  The experience was volcanic with its seismic aftershocks still reverberating through my psyche!  I’ve been in the meat industry no for 14 years.  Till my day with Etienne, I thought of MDM (Mechanically Deboned Meat) as something like flour or sugar, a commodity of uniform characteristics and quality.  Was I wrong!  It turns out that as is the case with all ingredient, functionality follows processing techniques.  Inspired by Etienne’s passion for MDM, I started to investigate  What a world started opening up!  I share some of my initial discoveries.

Definition

“Mechanically deboned meat (MDM), mechanically recovered meat (MRM) or mechanically separated meat (MSM) are synonyms used to mark the material, obtained by application of mechanical force (pressure and/ or shear) to animal bones (sheep, goat, pork, beef) or poultry carcasses (chicken, duck, turkey) from which the bulk of meat has been manually removed” (Hui, 2012)

There are a number of different methods to achieve this, but most of them result in cell breakage, protein denaturation, generally an increase in lipids and haeme groups and poorer mechanical properties.  (Hui, 2012)

MDM is mainly used in producing emulsion-type products such as Vienna’s, Russians, and Polony (in South Africa).  “Meat recovered from bones or carcass parts by mechanical procedures is generally considered to be of poor nutritional and microbiological quality”  (Hui, 2012)  In many parts of the world, strict legislation governs the use of these products.  When compared to the rest of the world, South Africa lags behind in this regard.  There are certain producers who choose to only use muscle meat in the production of its emulsion sausages, loaves, and hams, and the consumer is entirely left to study ingredients declarations to determine if MDM is present or not.  There are also a number of different qualities of MDM and it is by no means correct to claim that all MDM are of poor microbiological quality and share the same low nutritional characteristics.  The different production methods of MDM can broadly be separated into hard and soft MDM.

Hard MDM

Hard MDM is made from pork or beef where it will be hard to clear the bones from all the small meat bits.  It can be made from chicken also.  When the valuable pieces of chicken and turkey (wings, breasts, and legs) are removed, hard MDM is made from the carcass that is left.  In this method, the bones or carcass is placed in some kind of a pressure chamber with small holes in it and the bones or carcasses are subjected to high pressure which removes the skin, meat bits, connective tissue, etc. still stuck to the bones.  These pass through the small holes of the barrel sieve (around 0.5 – 0.8mm in diameter).  The basic principle remains the same across many different machines namely that high pressure is used to clean the bones.  (Feiner, 2006)

Hard MDM should not contain bone bits larger than the hole size of the sieve, but in reality, on account of the enormous pressure used to remove the fragments from the bones, they often do.  The consequences of the presence of bone pieces in the MDM elevates the calcium and phosphorus content in hards MDM quite high.  These, in turn, interferes with the functionality of phosphates in emulsion sausages.  (Feiner, 2006)

The micro status of hard MDM is of great importance.  The reason for the high micro in this MDM is the large surface area of the meat.  The levels should not be higher than normal minced meat.  As always, processing conditions play the key role here and low micro levels are never guaranteed. (Feiner, 2006)

Another problematic feature of hard MDM is the presence of bone marrow, particularly in chicken MDM.  This speeds up the oxidation of fat since bone marrow contains a fair amount of metals such as iron, magnesium, and copper “which acts in a pro-oxidative manner.” (Feiner, 2006)

The fat content of hard MDM is inconsistent.  Protein, fat and bacterial levels should be part of MDM specifications.  The shelf life of pork and chicken MDM is much shorter than beef MDM in both chilled and frozen state.  The reason is the fatty acids in pork and chicken have high levels of unsaturated fatty acids in the fat fractions when compared with beef.  “Rancidity develops quickly within such material.”  (Feiner, 2006)

MDM has a  pasty texture. Due to the meat recovery method, there is a high proportion of “pulverised muscle fiber residue.”  There is also a large proportion of “partly destructured muscle fibers.”  We call such change in muscle fiber ‘‘destructuration” (Sifre and others 2009)”  (Feiner, 2006)

Soft MDM

Soft MDM, on the other hand, is produced from meat trimmings, high in connective tissues.  The process avoids the enormous pressure of the hard MDM methods by the action of a roller on the meat.  In this system, the material is put through a machine that separates the meat from connective tissues, cartridge, etc. based on the different hardness of these components.  The process is much more productive in terms of time and input required when compared to the hard MDM methods.  In many instances, a “Baader” machine is used or something similar. (Feiner, 2006)

A very typical production method is as follows.

  1.  Grind minced meat through 13 – 20mm mincer plate;
  2.  Feed through Baader machine
  3. The Baader machine has small holes in a rotating drum and the meat passes under the drum so that the drum presses on the meat.  The soft lean meat, due to its texture, passes through the holes in the rotating drum and is collected there and fed out on the side of the machine;
  4. The harder connective tissue, bone fragments, etc. are ejected at the front of the machine, having been unable to be pass to the inside of the drum where only soft lean meat is collected. (Feiner, 2006)

Both the collected connective tissues, sinews, etc and the soft MDM from inside the drum has enormous functional applications and products are made from both.

Comparing hard MDM and soft MDM, the following functional differences emerge:

Soft MDM Hard MDM
Protein Content:  15% – 17% Protein Content:  12% to 15%
Of this, 70% to 80% is equal to protein found in muscle meat. Of this, 60% to 70% is equal to the protein found in muscle meat.
Consequently: Consequently:
– Much improved WBC (Water Binding Capacity); – Reduced ability to immobilise water
– Much improved ability to emulsify fat – Reduced ability to immobilise emulsify fat
70% to 80% WBC and emulsifying characteristics of lean muscle meat
All protein in soft MDM still functional Reason is: denaturing of proteins and cell breakage during processing.
Fine and mushy consistency
Consequently:
– Do not support firmness in final product
pH: between 6.2 and 6.4
Consequently:
– poor colour developmenty
– MDM only products exhibit a darker colour.

Legislation

Examples of legislation in place in many parts of the world related to MDM are the following:

Bones to be used in the production of Hard MDM must be stored at between 0 and 2 degrees C no longer than 24 hours or be frozen for a maximum of 8 days before it is processed.  If it is frozen, this must take place immediately after production.  The chilled bones must be utilized within 24 hours.

Besides these, fat percentages, minimum requirements on nutritional value, and percentage connective tissue are set in many countries.

Functional Characteristics

Despite the fact that many different MDM producers achieve these values, there exists an enormous range of varying functional characteristics of MDM, produced by different manufacturers, on account of different process and machines employed in its production.

Lets first evaluate meat that was recovered through deboning with meat processed with an MDM machine. Froning (1970) for example compared hard deboned white and dark chicken meat with chicken backs and necks and turkey frames processed with a Paoli machine and chicken backs processed with a Beehive deboner for emulsification properties. (McMillan, 1980)

He found that MDM was most stable in a bowl cutter to temperatures of 7.2 to 12.8 deg C. Above 12.8 deg C, the tensile strengths of finished emulsions decreased and the amounts of fat and gel-water released during processing increased. By comparison, the hand boned broiler meat was stable at all chopping temperatures.  (McMillan, 1980)

He further found that MDM had less protein matrix available for emulsion than hand-deboned meat, “due to greater collagen dispersion and possible loss of protein solubility caused by deboner protein denaturation.”  (McMillan, 1980)

The tests may have been conducted in the 1970s and 1980s, but the principals are equally valid.  Froning  et al. (1971) used 15% turkey MDM in red meat frankfurters to study its stability and acceptability. The MDM was produced with a Paoli deboning machine and the results indicated a higher capacity to emulsify oil per 2.5g sample than pork trimmings, but a reduced capacity than boneless cow meat.  (McMillan, 1980)

Turkey MDM  had a reduced WHC compared to red meat sources.  Gel-water loss was greater in frankfurters made with 15 percent turkey MDM.  Their research alluded me to another very important consideration in the functionality of MDM.  In SA, all MDM is sold frozen, but in other countries, MDM is customarily produced, sold and used unfrozen.  Froning  et al. found that frankfurters which fresh MDTM had less cook
than franks containing MDTM which was stored frozen for seven days prior to use.  (McMillan, 1980)

In terms of taste, no major differences were found between control frankfurters, frankfurters containing previously frozen turkey MDM and fresh MDM in terms of taste and colour.  The superiority of pure meat over MDM was confirmed by Schnell et al (1973).  They compared poultry MDM with hand boned carcass meat.  The texture frankfurters produced with hand-deboned meat was firmer than those produced with MDM. (McMillan, 1980)

Another interesting study, confirm the differences between different MDM producers was done by Baker et al. (1974).  They compared poultry MDM from three machines to measure the effect of chopping time on taste panel evaluation and frankfurter stability. “Chopping time had little effect on results of these tests, but source of the MDPM caused differences in frankfurter yield, stability during cooking, emulsion viscosity, and taste panel scores of texture and juiciness. More dense poultry MDM and smaller, more evenly distributed fat globules contributed to the stability of frankfurters with two of the poultry MDM sources as compared to the third MDPM source (Angel et al., 1974).  (McMillan, 1980)

Some researchers have reported that they were able to “manage” negative characteristics in certain MDM typed through various techniques such as controlling and altering the pH, but if this can be duplicated in a factory environment if questionable.

Foodnavigator reported in 2018 on a project in the EU seeking to test MDM in terms of the structural integrity as a key indicator for its quality. The software reportedly use image processing algorithms to quantify degrees of degradation in meat. The aim is to test cheap imports into the EU which claims comparability with high quality EU MDM.

In the EU, certain producers such as Polskamp Meat Industrie in Holland is able to produce MDM of exact specifications. Processors can choose fat content of ±11%, ±12%, ±14% and ±16% and protein content of between ±15% to ±18% The colour of their chicken MDM is consistent being the typical colour of fresh chicken meat of pink-red. This sets them apart from many producers who is unable to certify such exact parameters, again confirming our thesis that not all MDM are created equal!

Polskamp is a good example of using technology to overcome the inherent problems in hard MDM. They pioneered low pressure technology to remove meat from bones, thereby avoiding the negative aspects associated with high pressure meat separation.

They claim that their 3 millimeter meat is “produced using special machines that can separate meat from the bone. Contrary to mechanically separated meat, 3 millimeter meat is produced using low-pressure technology that better preserves the structure of the chicken meat. 3 Millimeter meat is also characterised by its lower calcium content and lighter colour. Polskamp Meat Industrie offers its buyers several types of 3 millimeter meat, e.g. a white product and a rose-coloured product.” (polskamp.com)

Conclusion

These and more recent studies indicate the need for the processor to conduct a thorough evaluation of its MDM source.  At the end of the day, all these studies point to the fact that the different MDM’s on the market, produced by various manufacturers, using a range of different source material’s are not all created equal.

By choosing the right MDM source, it may be possible to omit binding and water absorption material such as the different soya products or starches.  The effect of freezing and freezing time on MDM is another key aspect to be evaluated and along with aspects such as fat %, connective tissue%, and water content must command our careful attention.

Finally, careful attention should be given to the different methods to extend the shelf life of MDM by reducing lipid peroxidation and of microbial growth.

Even if pure meat products is our objective, the lessons found in the production of MDM and the subtle techniques of optimizing yield, profitability while achieving exceptional product quality will benefit us tremendously if we master it!

Further Reading

The nutritional and physical characteristics of mechanically proc

Hui, Y. H. (Editor) 2012. Handbook of Meat and Meat Processing. CRC Press.

Hiking photos

It is not every day that one turns 50.  Here are the rest of the photos from my hike up the Magaliesberg on 13 April 2019.

Hiking Photos – 50th birthday

References:

Feiner, G.  2006.  Meat Products Handbook: Practical Science and Technology.  Woodhead Publishing.

Hui, Y. H. (Ed.) 2012.  Handbook of Meat and Meat Processing. Chapter: Mechanical Deboning.  CRC Press; Taylor & Francis Inc.

McMillan, K. W..  1980.  The nutritional and physical characteristics of mechanically processed beef and pork product.  Iowa State University.  Retrospective Theses and Dissertations. 7342. https://lib.dr.iastate.edu/rtd/7342

https://polskamp.com/product/3-millimeter-meat/

Photo Credit:

Continental Franks: https://www.amazingfoodmadeeasy.com/define/charcuterie/what-is/frankfurters

All other photos by Eben

Soya: Review of some health concerns and applications in the meat industry

Introduction

Vagadia et al. (2015) state that soya “contains a variety of bioactive anti-nutritional compounds including protease trypsin inhibitors, phytic acid, and isoflavones that exhibit undesirable physiological effects and impede their nutritional quality. Inactivation of these trypsin inhibitors, along with deleterious enzymes, microbes, bioactive components and increasing the protein quality by improving its texture, colour, flavour, functionality and digestibility are the most important factors to be considered in the crucial stage in the manufacturing of soy products.”  Are there reasons to be concerned and what can we learn about its history and possible applications in the meat industry?

Historically Valued Plant

Before we break down the concerns raised by Vagadia et al. (2015), it is instructive to know that soya has been consumed in many countries since before recorded history.  A rich tradition developed around its use in medicine from antiquity.    Duke (1991) showed that a search of his “Medicinal Plants of the World” database (Sept. 1981) indicated that soybeans are or have been used medicinally in China to treat the following symptoms/diseases or for the following medicinal properties (listed alphabetically; Most information from: Li Shih-Chen. 1973. Chinese Medicinal Herbs. San Francisco: Georgetown Press):

“Abortion, ague, alcoholism, anodyne, antidote for aconite or centipede or croton, antivinous, anus, apertif, ascites, ataxia, blindness, bone, bugbite, burn, carminative, chestcold, chill, circulation, cold, complexion, decongestant, diaphoretic, diuretic, dogbite, dysentery, dyspnea, eczema, edema, enuresis, feet, fever, halitosis, headache, hematuria, impotence, intoxication, kidney, labor, laxative, leprosy, malaria, marasmus, marrow, melancholy, metrorrhagia, nausea, nervine, ophthalmia, pile, pregnancy, preventive (abortion) puerperium, refrigerant, resolvent, rheumatism, scald, sedative, skin, smallpox, snakebite, sore, splenitis, splinter, stomach, tinea, venereal, vertigo, vision.”

Uses in other parts of the world include cancer, and cyanogenetic, shampoo (USA), diabetes (Turkey), soap (Asia), stomach problems (India).

Not only was it recognized as a superfood in many parts of the world, but it was celebrated for its medicinal value.  Looking at the factors of concern raised by many, we begin by looking at the most well-known concern factor of its role as a trypsin inhibitor.

Trypsin Inhibitors

The German physiologist Wilhelm Kühne (1837-1900) discovered trypsin in 1876. It is an enzyme that cleaves peptide bonds in proteins (serine protease) and is therefore essential in digestion.   It is found in the digestive system of many vertebrates, where it hydrolyzes proteins. (Kühne, 1877)  Trypsin is formed in the small intestine when its proenzyme form, the trypsinogen, produced by the pancreas, is activated. (Engelking, 2015)  A trypsin inhibitor (TI) is then something (a protein) that reduces the biological activity of trypsin and as such have a negative effect on nutrition by impairing the digestion of food.

The concern about soya’s trypsin inhibitors is of no real concern to us.  It turns out that trypsin in humans is more resistant to inhibition than is the trypsin of other mammalian species. “The effect on human trypsin of soybean trypsin inhibition in soy protein does not appear to be a potential hazard to man. Therefore, the elimination of STI does not seem to be necessary for humans.”  (Flavin DF, 1982)

“In animal diets, however, pancreatic toxicity must be considered whenever soybean protein is utilized. Soybeans should be treated to increase their nutritional benefits and decrease any animal health risks. This will ensure healthy control subjects in laboratory situations and avoid misinterpretation of pathologic data.

The treatment suggested is heat since heat will destroy most of the soybean trypsin inhibitors. Additional supplementation is required following heat treatment for amino acids such as methionine, valine, and threonine; for choline; and for the minerals zinc and calcium.  Excessive heat must be avoided since it will decrease the nutritional value of soybean protein and increase lysinoalanine, a nephrotoxic substance.

Finally, the use of STI as a promotor in the study of potential pancreatic carcinogens may prove beneficial for cancer research and might be considered in the future.” (Flavin DF, 1982)

Phytic acid

Phytic acid also is suspect due to its inhibitory effect related to nutrition.  Anderson (2018) states “It is a unique natural substance found in plant seeds. It has received considerable attention due to its effects on mineral absorption. Phytic acid impairs the absorption of iron, zinc, and calcium and may promote mineral deficiencies”  (Arnarson, 2018)

As is the case with the trypsin inhibition, the story is a bit more complicated than that because phytic acid also has a number of health benefits.

Anderson writes that “phytic acid, or phytate, is found in plant seeds. It serves as the main storage form of phosphorus in the seeds. When seeds sprout, phytate is degraded and the phosphorus released to be used by the young plant. Phytic acid is also known as inositol hexaphosphate, or IP6. It’s often used commercially as a preservative due to its antioxidant properties.

Phytic acid is only found in plant-derived foods. All edible seeds, grains, legumes and nuts contain it in varying quantities, and small amounts are also found in roots and tubers. The following table shows the amount contained in a few high-phytate foods, as a percentage of dry weight:

Phytic Acid in food

As you can see, the phytic acid content is highly variable. For example, the amount contained in almonds can vary up to 20-fold.

Phytic acid impairs absorption of iron and zinc, and to a lesser extent calcium.  This applies to a single meal, not overall nutrient absorption throughout the day.  In other words, phytic acid reduces mineral absorption during the meal but doesn’t have any effect on subsequent meals.  For example, snacking on nuts between meals could reduce the amount of iron, zinc and calcium you absorb from these nuts but not from the meal you eat a few hours later.

However, when you eat high-phytate foods with most of your meals, mineral deficiencies may develop over time.  This is rarely a concern for those who follow well-balanced diets but may be a significant problem during periods of malnutrition and in developing countries where the main food source is grains or legumes.

Avoiding all foods that contain phytic acid is a bad idea because many of them are healthy and nutritious.  Also, in many developing countries, food is scarce and people need to rely on grains and legumes as their main dietary staples.

Phytic acid is a good example of a nutrient that is both good and bad, depending on the circumstances.  For most people, it’s a healthy plant compound. Not only is phytic acid an antioxidant, but it may also be protective against kidney stones and cancer.  Scientists have even suggested that phytic acid may be part of the reason why whole grains have been linked with a reduced risk of colon cancer.

Phytic acid is not a health concern for those who follow a balanced diet.  However, those at risk of an iron or zinc deficiency should diversify their diets and not include high-phytate foods in all meals.  This may be especially important for those with an iron deficiency, as well as vegetarians and vegans.

There are two types of iron in foods: heme iron and non-heme iron.  Heme-iron is found in animal foods, such as meat, whereas non-heme iron comes from plants.

Non-heme iron from plant-derived foods is poorly absorbed, while the absorption of heme-iron is efficient. Non-heme iron is also highly affected by phytic acid, whereas heme-iron is not.  In addition, zinc is well absorbed from meat, even in the presence of phytic acid.

Therefore, mineral deficiencies caused by phytic acid are rarely a concern among meat-eaters.  However, phytic acid can be a significant problem when diets are largely composed of high-phytate foods while at the same time low in meat or other animal-derived products.  This is of particular concern in many developing nations where whole grain cereals and legumes are a large part of the diet.”  (Arnarson, 2018)

Isoflavones

Isoflavones are a class of phytoestrogens — plant-derived compounds with estrogenic activity. Soybeans and soy products are the richest sources of isoflavones in the human diet.  (oregonstate.edu)

“Since many breast cancers need estrogen to grow, it would stand to reason that soy could increase breast cancer risk. However, this isn’t the case in most studies.

In a review of 35 studies on soy isoflavone intake and breast cancer incidence, higher soy intake reduced breast cancer risk in both pre- and postmenopausal Asian women.  For women in Western countries, one study showed soy intake had no effect on the risk of developing breast cancer.

This difference may be due to the different types of soy eaten in the Asian compared to the Western diet. Soy is typically consumed whole or fermented in Asian diets, whereas in Western countries, soy is mostly processed or in supplement form.

In an animal study, rats fed fermented soy milk were 20% less likely to develop breast cancer than rats not receiving this type of food. Rats fed soy isoflavones were 10–13% less likely to develop breast cancer.  Therefore, fermented soy may have a more protective effect against breast cancer compared to soy supplements.  Additionally, soy has been linked to a longer lifespan after breast cancer diagnosis.

In a review of five long-term studies, women who ate soy after diagnosis were 21% less likely to have a recurrence of cancer and 15% less likely to die than women who avoided soy.”  (Groves, 2018)

From the above notes, it may appear that it is perfectly safe for humans to consume raw soya.  There is however one very good reason to cook soya well before it is consumed.

Lectin Effects

“Soybeans contain lectins, glycoproteins that bind to carbohydrates in cells. This can damage the cells or lead to cell death in the gastrointestinal tract. Lectins may bind to the intestinal walls, damaging the cells and affecting nutrient absorption as well as causing short-term gastrointestinal side effects. Unlike most proteins, lectins aren’t broken down by enzymes in the intestine, so the body can’t use them. Lectins can affect the normal balance of bacteria in the intestine and the immune system in the digestive tract.” (Perkins, 2018)

Dr. Mark Messina discussed the issue with Lectin in soya in a brilliant article entitled “Is Soybean Lectin an Issue?”  He writes, “Given all the attention they’re receiving, you might think these proteins are newly discovered, perhaps because of a sudden advance in technology. Given all the concerns being raised about them, you might be thinking of avoiding foods that contain them. If you do, you can pretty much say goodbye to a long list of healthy foods such as legumes (including soy and peanuts), eggplant, peppers, potatoes, tomatoes, and avocados. Despite the hoopla, studies show there is little reason for concern.

Lectins are anything but new to the scientific community. They are a class of protein that occurs widely in nature and have been known to exist in plants for more than a century. Much of the lectin research has focused on legume lectins but these carbohydrate-binding proteins are widely distributed throughout the plant kingdom. The lectin in soybeans was discovered in the 1950s.

In plants, lectins appear to function as nitrogen storage compounds, but also have a defensive role, protecting the plant against pests and predators. They are capable of specific recognition of and binding to carbohydrate ligands. The term lectin (legere = Latin verb for to select) was coined by Boyd circa 1950 to emphasize the ability of some hemagglutinins (lectins) to discriminate blood cells within the ABO blood group system.5-The term lectin is preferred over that of hemagglutinin and is broadly employed to denote “all plant proteins possessing at least one non-catalytic domain, which binds reversibly to a specific mono- or oligosaccharide.”

Orally ingested plant lectins remaining at least partially undigested in the gut may bind to a wide variety of cell membranes and glycoconjugates of the intestinal and colonic mucosa leading to various deleterious effects on the mucosa itself as well as on the intestinal bacterial flora and other inner organs. The severity of these adverse effects may depend upon the gut region to which the lectin binds. Several cases of lectin poisoning due to the consumption of raw or improperly processed kidney beans have been reported.

The lectin content of soybeans varies considerably among varieties, as much as fivefold. However, from a nutritional perspective, it is the amount in properly processed soyfoods that is most relevant. Although there has been a lot of debate about whether even active soybean lectin is harmful,  a true pioneer in this field, Irvin E. Liener, concluded that soybean lectin isn’t a concern because it is readily inactivated by pepsin and the hydrolases of the brush border membrane of the intestine. But, others think soybean lectin does survive passage through the small intestine.

Not surprisingly, autoclaving legumes including soybeans completely inactivates lectins. However, foods aren’t typically autoclaved. The most practical, effective, and commonly used method to abolish lectin activity is aqueous heat treatment. Under conditions where the seeds are first fully soaked in water and then heated in water at or close to 100°C, the lectin activity in fully hydrated soybeans, kidney beans, faba beans, and lupin seeds is completely eliminated.  Thompson et al. noted that cooking beans to the point where they might be considered edible are more than sufficient to destroy virtually all of the hemagglutinating activity of lectins. More recently, Shi and colleagues23 found that soaking and cooking soybeans destroyed more than 99.6% of the lectin content, which agrees with earlier work by Paredes-Lopez and Harry.

Finally, evidence from clinical trials in no way suggests that the possible residual lectin content of soyfoods is a cause for concern. Adverse effects typically associated with lectin toxicity don’t show up in the hundreds of clinical trials involving a range of soy products that have been published. Not surprisingly, the U.S. Food and Drug Administration recently concluded that soy protein is safe.”  (Messina, 2018)

Saponins in Soybeans

Saponins in soya are responsible for the bitter taste, foam-forming, and activities that rupture or destroy red blood cells.  Its presence in soya is probably an evolutionary development to protect it against, for example, Callosobruchus chinensis L., a common species of beetle.  Its protecting properties can be seen for example by the fact that [certain strains of] the first instar larvae, after burrowing beneath the seed coat, subsequently die without moulting. (Applebaum, 1965)

There are five known soya saponins: Soya sapogenols A, B, C, D, and E.  Saponins cannot be inactivated by cooking because cooking doesn’t break down this toxin like it does lectins.”  (Perkins, 2018)  “Triterpenoid saponins in the mature soybean are divided into two groups; group A soy saponins have undesirable astringent taste, and group B soy saponins have health-promoting properties. Group A soy saponins are found only in soybean hypocotyls, while group B soy saponins are widely distributed in legume seeds in both hypocotyls (germ) and cotyledons. Saponin concentrations in soybean seed are ranged from 0.5 to 6.5%.”  (Hassan, 2013)

Bondi and Birk (1966) investigated soybean saponins as related to the processing of petroleum etherextracted meal for feed and to the preparation of soy foods.  They found that “soybean saponins are harmless when ingested by chicks, rats and mice even in a roughly threefold concentration of that in a 50% soybean meal supplemented diet.” They are decomposed by the caecal microflora of these 3 species. Their non-specific inhibition of certain digestive enzymes and cholinesterase is counteracted by proteins which are present in any natural environment of these saponins. The haemolytic activity of soybean saponins on red blood cells is fully inhibited by plasma and its constituents –
which naturally accompany red cells in blood. Soybean saponins and sapogenins are not absorbed into the blood-stream (Note: Or perhaps not observed in the bloodstream). It may, therefore, be concluded that haemolysis – one of the most significant in vitro [in glass/test tubes] properties of soybean saponins and others–bears no ‘obligation’ for
detrimental activity in vivo [in living organisms].”  (Bondi, et al, 1966)

Birk, et al, 1980, found that “saponins are glycosides that occur in a wide variety of plants. They are generally characterized by their bitter taste, foaming in aqueous solutions, and their ability to hemolyze [break down] red blood cells. The saponins are
highly toxic to cold-blooded animals, their toxicity being related to their activity in lowering surface tension. They are commonly isolated by extraction of the plant material with hot water or ethanol.”  (Birk, 1980)  Leaching the saponins out of the soybeans, removing the bitter taste.  (Perkins, 2018)

Applications and History

Reviewing the history of the development of soya industry in Israel, brought up some interesting perspective on its application in food.

“Hayes Ashdod was one of Israel’s first company to make foods from soybeans and Israel’s first manufacturer of modern soy protein products. In 1963 the company launched its first product, a soy protein concentrate named Haypro. This product was also the first commercial soy protein concentrate manufactured outside the United States. The main applications for Haypro were as a meat extender.”  (Chajuss, 2005)

“In 1966 Hayes Ashdod Ltd. introduced texturized soya protein concentrates under the brand names Hayprotex and Contex. Hayprotex was designed for use mainly as a minced
meat extender, while Contex was designed mainly for vegetarian analogs.”  (Chajuss, 2005)

“Concerning early textured soy protein concentrates: Hayes Ashdod introduced Hayprotex and Contex in 1966, and a company we are well familiar with for making nitrite curing of meat commercially available around the world through their legendary Prague Powder, the Griffith Laboratories from Chicago introduced GL-219 and GL-9921 in 1974, and Central Soya introduced Response in 1975.”  (Chajuss, 2005)

“In 1969 Hayes started to produce Primepro, a more functional and soluble soy protein concentrate, by further treatment of the aqueous alcohol extracted soy protein concentrate (Haypro), for use as substitutes for soy protein isolates and for caseinates in various food systems, especially in the meat processing industries.”  (Chajuss, 2005)

Further reading

A tremendous resource on research on soya is HISTORY OF SOYBEANS AND SOYFOODS IN THE MIDDLE EAST

Conclusion

Soya is a tremendous food and protein source.  The health concerns are addressed at the manufacturing stage.  Application of isolates, concentrates and TVP are multiple.  Even today, after being available on the market for so many years, all its various applications in foods have not been exhausted.  We are limited only by our imagination and interesting work remains to integrate its use into modern meat processing plants.

Reference

Applebaum, S.W.; Gestetner, B.; Birk, Y. 1965.  Physiological aspects of host specificity in the Bruchidae–IV.  Developmental incompatibility of soybeans for Callosobruchus. J. of Insect Physiology 11(5):611-16. May.

Arnarson, A.  2018. Phytic Acid 101: Everything You Need to Know.

Birk, Yehudith; Peri, Irena. 1980. Saponins. In: I.E. Liener, ed. 1980. Toxic Constituents of Plant Foodstuffs. 2nd ed. New York: Academic Press. xiv + 502 p. See p. 161-182. Chap. 6.

Bondi, A.; Birk, A. 1966. Investigation of soybean saponins as related to the processing of petroleum ether-extracted meal for feed and to the preparation of soy foods, to provide information basic to improving the nutritional value of soybean protein products. Rehovot, Israel: Hebrew University. 80 + xvii p. USDA P.L. 480. Project no. UR-A10-(40)-18. Grant no. FG-IS-112. Report period 1 March 1961 to 28 Feb. 1966. Undated. 28 cm.

Chajuss, D.. 2005. Brief biography and history of his work with soy in the USA and Israel. Part II (Interview). SoyaScan Notes. Feb. 19. Followed by numerous e-mails. Conducted by William Shurtleff of Soyfoods Center.

Duke, J. A. 1991. Research on biologically active phytochemicals in soybeans (Interview). SoyaScan Notes. Oct. Conducted by William Shurtleff of Soyfoods Center.

Engelking, Larry R. (2015-01-01). Textbook of Veterinary Physiological Chemistry (Third Edition). Boston: Academic Press. pp. 39–44. ISBN 9780123919090.

Flavin DF. The effects of soybean trypsin inhibitors on the pancreas of animals and man: a review. Review article. Vet Hum Toxicol. 1982. 1982 Feb;24(1):25-8.

Groves, M..  2018.  Is Soy Good or Bad for Your Health?

Hassan, S. M..  2013.  Soybean, Nutrition, and Health.  Intech  http://dx.doi.org/10.5772/54545

Kühne, W. 1877. “Über das Trypsin (Enzym des Pankreas)”, Verhandlungen des naturhistorisch-medicinischen Vereins zu Heidelberg, new series, vol. 1, no. 3, pages 194-198

Messina, M.  2018.  Is Soybean Lectin an Issue?  The Soy Nutrition Institute
The latest findings in soy health research, https://thesoynutritioninstitute.com

Perkins, S.  2018. What Happens if You Eat Raw Soybeans?

Vagadia, B. H., Vanga, S. K., Raghavan, V. 2015.  Inactivation methods of soybean trypsin inhibitor – A review. Received 14 December 2015, Revised 21 January 2017, Accepted 19 February 2017, Available online 27 February 2017. Elsevier. Trends in Food Science & Technology, Volume 64, June 2017, Pages 115-125

https://lpi.oregonstate.edu/mic/dietary-factors/phytochemicals/soy-isoflavones

Image Credit: https://semillasdealegria.com/products/soya?variant=29970856133