Notes on Comminution and Digestability

Notes on Comminution and Digestability
Eben van Tonder
11 Sptember 2021

Introduction

I am now 52 years old and have two teeth missing and one is cracked which the dentist suggested I don’t have anything done too until I replaced the two missing ones with implants. It goes with the territory of being 50+! ūüôā I discovered that it is much harder for me to eat meat with two molars missing and one that I cant use to chew. I recently bought a liquidiser and started to make fruit and vegetable smoothies for lunch and supper. A world opened up for me!

After making smoothies morning, evening and at night for a few weeks now, I understand much more about bowl cutting. In fact, my first lesson teaching bowl cutting techniques will in the future start with a liquidiser. After a week, I had good cause to suspect that I digest my food much better than before which made me re-look at the relationship between comminution and digestibility. More broadly, I ask the question what are the different factors influencing digestibility from the perspective of food preparations.

I give the notes based on extensive quotes from two studies.

The Li Study (2017) on Pork Digestability

The first study I referenced was that of Li (2017) where they compared digestability when pork products were prepared by cooking, emulsifying in emulsified-type sausage, dry-cured and stewed pork. The pH was adjusted to 2 after which gastric pepsin and trypsin were used to digest. After incubation at 37oC for 2 hours, pH was adjusted to 7.5. The pork sausages were cooked at 72oC. “The in vitro digestibility was expressed as the percentage of the difference in protein contents before and after digestion.” (Li, 2017)

The results of the Li (2017) study is as follows:

Pork products were made with pork longissimus dorsi muscles from the same carcasses.

  • The four products evaluated showed a “significant differences in protein digestibility.”
  • Highest digestability was emulsion-type sausage at both conditions.
  • The lowest digestability was stewed pork, after pepsin digestion alone, followed by trypsin digestion,
  • Cooked pork and dry-cured pork had similar digestability after pepsin digestion. Dry-cured pork was lower in digestibility than cooked pork after trypsin digestion.

I give their methods of preparing the experiments with each relevant discussion point grouped together for each of the 4 preparation methods.

Stewing

Preparation: Stewed pork was prepared according to the following formulations: pork muscle was vertically divided into strips (5 cm width) and cooked. The stewing was done as follows: Pork strips were blanched in boiling water for 5 min, chilled and cut into 5 √ó 5 √ó 5 cm cubes. The cubes were pan-fried (180 ¬įC) for 5 min with soybean oil (10 g kg‚ąí1 of meat) on a pot-induction surface. The cubes were fried and turned twice at an interval of 60 s (skin side not fried) and then cooked in boiling water (water/meat: 1/4) for 5 min. After that, the cubes were stewed at 100 ¬įC for 150 min. Eight replicates were applied for each product.

Discussion: “For stewed pork, long-time cooking may induce proteins to oxidation and aggregation that affects proteolytic susceptibility.” In the present study, stewed pork was cooked at higher temperature and for much longer time than the other three pork products, which may cause a higher level of protein oxidation and aggregation, and lower digestibility. The difference in digestibility between Bax et al. (2012) and the present study could be attributed to distinct cooking time (0.5 h vs. 1.5 h).

Dry Cured Pork

Preparation: Dry-cured pork was prepared as follows: curing with 5% salt and sun-drying for one month. The dry-cured pork was softened in hot water and cooked to the center temperature of 72 ¬įC.

Discussion: For dry-cured pork, salting and drying are two critical steps, during which protein surface hydrophobicity increases and dehydration, oxidation and aggregation occur as well.

Cooked Pork

Preparation: Cooked pork was prepared according to the following steps: pork muscle was cut vertically into 15 √ó 10 √ó 5 cm pieces that were packed in retort pouch and directly cooked in water bath till the center temperature reached 72 ¬įC.

Discussion: Cooking temperature has a distinct influence on the proteolytic susceptibility of myofibrillar proteins to digestive enzymes. At 70 ¬įC, moderate denaturation happens to meat proteins with the exposure of more protein cleavage sites accessible to digestive enzymes. However, protein oxidation and aggregation would increase at 100 ¬įC or higher temperatures, which is a condensing effect (Promeyrat, Bax, Traore, Aubry, Sante-Lhoutellier & Gatellier, 2010), but meat protein overall digestibility would be improved at high temperature (Bax et al., 2012).

Emulsion Sausages

Preparation: Emulsion-type sausage was prepared according to the following formulation: pork muscle and back fat at a ratio of 4 to 1, salt (1.8%) and tripolyphosphate (0.4%). Meat and fat were chopped using a high-speed chopper during which salt and tripolyphosphate were mixed, and the batter was stuffed into 48-mm-diameter plastic casings. The sausages were cooked till the centre temperature reached 72 ¬įC.

Discussion: Although emulsion-type sausage, dry-cured pork and cooked pork were cooked at the same temperature (70 ¬įC), an emulsifying system was formed during the preparation of emulsion-type sausage, and the fat droplets around muscle fibres would decrease protein oxidation and aggregation (Youssef, Barbut, & Smith, 2011), and thus increase the digestibility.

Conslusion from Li (2017) Study

The Li (2017) study introduced me to factors impacting digestibility such as oxidation and aggregation along with the fascinating effect of fat on this process in fine comminuted products. Further, cooking times and temperatures and their impact on aggregation and compacting as temperatures rich 100oC. I have an interesting story about this. A few months ago I was testing an emulsion type sausage and the cooking pot malfunctioned, boiling the sausage at 100oC for half an hour. When I opened the cooking pot and discovered this the natural hog casings I used were all cooked off but amazingly the sausages aggregated and compacted to such an extent that the sausages were all still almost perfectly intact.

Casing cooked off at 100o C for 30 minutes. A good example of aggregation.

Casing cooked off at 100o C for 30 minutes. A good example of aggregation.

When I repeated this at 72oC I did not nearly have the same “compacting” effect. The products were made with 45% MDM and 10% product which I made from beef hide. The sausages that I made with the same inclusion of MDM but 10% product I made from collagen did not have the same dramatic effect of compacting and aggregation. By adding these materials I obviously moved outside a direct application of the Li (2017) study, but the observations are nevertheless fascinating and the points of aggregation and compacting are well demonstrated.

Farouk (2019) Study on Beef-Centric Meals Digestability

I give the different aspects they investigated and their conclusions.

Animal Age

Beef protein was highly digestible regardless of the age of animal from which the meat was collected (4-day-old calf, 18- to 24-month-old bull, or 6-year-old cow).

Rigor State

The time of sampling of LD muscle (prerigor, from 50 min through 200 min postmortem) had little influence on the digestibility of beef proteins, and this was not markedly affected by rigor at 48 h.

Ultimate pH

The proteins of high ultimate pH meat digested faster than their low ultimate pH equivalent. Densitometry measurements of each gel lane were used to calculate digestion efficiencies and rates for each of the treatment combinations. Physiological and biochemical mechanisms underpinning the greater digestibility of high ultimate pH beef have been discussed by Farouk et al..

Muscle/ Meat Cuts

While there were few differences up to 5 min, by 60 min supraspinatus appeared more digested (fewer and fainter protein bands), suggesting that this cut might be faster and more thoroughly digested.

Mincing/Particle Size

There was little effect of particle size on the digestibility of cooked proteins in meat. Exposure of meat proteins to pepsin activity in vitro should have been much greater for the finely milled substrate, yet this did not markedly influence the rate or extent of proteolysis. Note that the samples were milled and not finely chopped in a bowl cutter or similar. Particle size was therefore still relatively large,

Organ Meats

The structure and composition of organ meats is substantially different from muscle meat, and this has consequences for digestion. For instance, the protein content of the heart, kidney and spleen from prime steers was 10‚Äď27% less on a fresh-weigh basis. Digestion commenced at a significantly faster pace for the kidney and liver compared to muscle, when evaluated as the relative digestibility of T5. The lower molecular weight and globular nature of the kidney and liver proteins likely contribute to their faster in vitro digestibility.

Discussion: Animal organ meat, sometimes referred to as offal or the fifth quarter of a carcass, is only a minor contribution to typical Western diets for a variety of reasons, thus missing out on its potential culinary and nutritional values. Connective tissue substances are resistant to in vitro digestion with pepsin and so lowered the total relative peptic digestibility of calf beef compared to the older cattle. They were more digested (less intense) in prerigor bull beef than in 48 h postrigor, in less collagenous cuts compared to higher rcontaining cuts, and in finely ground milled meat compared to coarsely smashed meat.

Meat Accompaniments

An online survey of menus from New Zealand and Australia restaurants revealed that the most common accompaniments served with red meat were potato, onion, mushroom, tomato, rice, noodle, bean, and carrot. This is varied slightly by country and markedly by cuisine. For instance, in New Zealand, noodle, rice, and bean were more popular at Asian restaurants, while potato, mushroom, and tomato were more popular with European cuisine.

SDS PAGE separation of proteins and peptides in the digesta of beef cooked with the top five accompaniments plus pumpkin showed that meats from all three age categories of animals (4-day-old calf, 18- to 24-month-old bull, or 6-year-old cow) were most digestible when cooked with mushroom, whereas digestion was least efficient when the meats were cooked with rice and potatoes. Based on relative digestibility calculation and averaging over all animal ages, the rank order of protein digestibility was found to be mushroom > pumpkin > onion = tomato > rice > potato.

Bull meat cooked with mushrooms was very effective in promoting digestion through the gastric and intestinal phases. In contrast, meat cooked by itself did not digest completely even after 240 min.

Enhanced digestion from cooking with mushroom (and pumpkin) could be due to the presence of endogenous proteolytic enzymes in these vegetables that were not present in the other accompaniments.

Conclusions from the Farouk (2019) Study

Prerigor, low collagen supraspinatus muscle finely ground prior to cooking would be judged more digestible than the alternatives in these experiments.

Sustainable production of animals as a source of food demands that we make full use of every carcass. Unlocking the potential of the less familiar cuts and promoting their inherent benefits is an important role for nutritional research. Beef organ meats/ofals such as liver and kidney were more digestible than muscle meat from the same carcass.  This suggests new opportunities for organ meat as a versatile ingredient, perhaps by formulating highly digestible animal protein foods for infants with less developed GIT or for elder consumers with compromised GIT function.  The soft texture and minimal myofribril content of the liver and kidney also offer functionality. These could be a valuable resource for the 1st and 3rd age consumer groups who struggle with chewing and swallowing muscle meat.

Well-informed combining can also produce beneficial biochemical synergies. For instance, consuming orange juice that contains ascorbic and citric acids will enhance the bioavailability of ferric iron in plant foods. It is possible that some accompaniments affect the digestion of food and so might be chosen to optimise benefits for a particular consumer or to better suit an occasion.

Regarding the effect of cooking, it is important to note that cooking meat on its own has variable effects on meat digestibility depending on both temperature and time. For instance, peptic digestibility of beef is lowered, and pancreatic digestibility is enhanced when meat is cooked quickly to 100¬įC, with longer cooking at the same temperature reducing overall susceptibility of meat proteins to proteolytic enzymes; cooking pork mildly at 70¬įC enhanced peptic digestion, while at 100¬įC slowed peptic digestion. In the present study, the combined meat and accompaniments were cooked at 100¬įC; cooking at this temperature with some of the accompaniments improved the digestibility of muscle meat from animals of all ages; Mushroom affected the bull beef. Note that even the resistant proteins near 42‚Äď40 kDa were digested by T30. A zymogram of the enzymes in extracts of accompaniments revealed proteolytic enzymes in mushroom and pumpkin. These enzymes may be contributing to digestibility. Mushroom and pumpkin are known to contain proteolytic enzymes, but their effects on wholetissue digestion had not been demonstrated.

Within the parameters of the present study, beef was observed to be more digestible or digested faster when it came from an older animal, at prerigor, and when it had high ultimate pH or contained less collagen content. Some beef organ meats were more digestible than beef muscle. Digestibility improved when meat was cooked with vegetables that contain proteolytic enzymes and diminished slightly with carbohydrate-rich or starchy foods such as rice and potatoes.

References

Factors Affecting the Digestibility of Beef and Consequences for Designing Meat-Centric Meals. Farouk, M. F., Wu, G., Frost, D. A., Staincliffe, M., and Knowles, S. O..

Li, L., Liu, Y,. Zou, X., He, J., Xu, X., Zhou, G., Li, C.. 2017. In vitro protein digestibility of pork products is affected by the method of processing. Food Research International 92 (2017) 88‚Äď94; Elsevier.



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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 ‚ÄúMedicinal Plants of the World‚ÄĚ 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):

‚ÄúAbortion, 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.‚ÄĚ

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 K√ľhne (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. (K√ľhne, 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‚Äôs 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¬†‚ÄĒ¬†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‚Äôt 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‚Äď13% 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‚Äôre 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 ‚Äúall plant proteins possessing at least one non-catalytic domain, which binds reversibly to a specific mono- or oligosaccharide.‚ÄĚ

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‚Äôt 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¬įC, 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‚Äôt 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.‚ÄĚ 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 ‚Äď
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 ‚Äď one of¬†the most significant in vitro [in glass/test tubes] properties of¬†soybean saponins and others‚Äďbears no ‚Äėobligation‚Äô for
detrimental activity in vivo [in living organisms].‚Ä̬† (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‚Äôs first company to¬†make foods from soybeans and Israel‚Äôs 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‚ÄďIV.¬†¬†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‚Äď44.¬†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

K√ľhne, W. 1877. “√úber 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 ‚Äď 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