The Impacts of Cooking and Processing on Digestibility of Proteins

Studies in developing countries like Brazil, India, and Guatemala have shown that the communities there rely heavily on indigenous foods, which have lower protein digestibility than the typical diet in North America, with values ranging from 54% to 78% and 88% to 94%, respectively (Alonso, Aguirre, and Marzo, 2000, p. 159). The traditional diets are typically centered on unprocessed grains, legumes, and cereals that are high in insoluble fiber, less digestible protein ratios, and antinutrients that slow down the rate at which proteins are digested (Friedman & Brandon, 2001, p.1069). This study will review effects of the presence of the anti-nutritional factor in proteins and how they interfere with the digestibility of food and feed items.

Anti-nutritional Factors

These are elements found in food and feed items and may adversely affect the availability of amino acids and the ability to digest proteins (Gilani, Cockell, and Sepehr, 2005, p. 987). The factors may be naturally found in mustard and items that contain protein from rapeseed in the form of glucosinolates, and in legumes as hemagglutinins and the inhibitors of trypsin. They also have been identified in other cereals and oilseed as tannins and phytates respectively, and in protein commodities of cottonseed in the form of gossypol (Kgomotso & Chiu, 2008, p. 1457). Heating and chemical manufacturing may lead to the formation of anti-nutritional elements especially in protein food items, processing of Maillard complexes, lysinoalanine, varieties of oxidized Sulphur amino acids, and D-amino acids.

Tests done on rats and pigs divulged that digestibility of amino acids and proteins may be reduced significantly due to the heightened concentration of dietary inhibitors of trypsin (Millward, Layman, Tomé, and Schaafsma, 2008). A similar effect was witnessed with high quantities of tannins that are found in cereals like sorghum, as well as legumes like fava bean (Propst, Flickinger, Bauer, Merchen, and Fahey, 2003, p. 3058). Further studies pertaining to supplemented levels of phytase production for pigs and poultry showed unrelated evidence of reduced amino acid and protein digestion.

Caseins such as insulates of soy protein, wheat protein, and lactalbumin may form D-amino acids upon heating. They have a digestible level that is lower than 40% and can lower the overall capacity to break down proteins by about 28% as witnessed in pigs and mice (Schaafsma, 2000, pp. 1865S-1866S). Age was identified to be an element that determines the level of susceptibility to the harmful effects of anti-nutrition factors. As observed, older rats are more prone to the effects than younger ones (Smith and Caldwell, 2001, p. 261). Researchers found that application of data obtained by observing tests done on young rats as the recommended model animal to compute Protein Digestibility-Corrected Amino Acid Score (PDCAAS) may lead to an exaggeration of the value of items and the ability to break down proteins, such as those that have anti-nutritional aspects for the aged population(Smith and Caldwell, 2001, p. 261).

Oxidative Proteins Modifications

External factors, biochemical reactions, and metabolic processes lead to a continuous process of formation of radicals in living cells. Some radicals may be essential to physiological activities. Therefore, there is no guarantee of protection from the harmful effects of radicals by the antioxidant protective system (Tang, Moore, Kujbida, Tarnopolsky, and Phillips, 2009, p. 987). The oxidation processes are harmful to the DNA as shown by experiments on animals as well as in vitro and are critical aspects of carcinogenesis. Irrespective of wide repairs, DNAs that are altered by oxidation are found in plenty within human tissues especially in the form of tumors, that is, about 1 to 200 altered nucleosides in 105 unbroken nucleosides (Smith and Caldwell, 2001, p. 263). Over time, the damaged nucleosides grow in both mitochondrial and nuclear DNA. The outcomes as a result of lesion repair are excreted through urine at a similar rate to that of damage of up to 104 alterations per cell daily (Smith and Caldwell, 2001, p. 264). 8-oxo-7 and 8-oxide are the most abundant and mutagenic lesions that lead to GT transversions that exist in genes pertaining to a tumor (Alonso et al., 2000, p. 160).

Studies on oxidative changes base and sugars that occur within the DNA are usually given less priority in studies since their biological relevance is not clear. Biomarkers indicating the presence of damaged oxidative DNA in human beings include the presence of oxidized nucleoside and repair base elements in the urine, and changes in DNA singled out from the affected tissues or substitute cells like lymphocytes (Alonso et al., 2000, p. 161). The biomarkers are usually indicative of the extent of damage and repair. They have also been used to study important factors in human beings (Friedman and Brandon, 2001, p. 1070). Ionized radiation has been found to have an oxidative DNA harm for both urinary and leukocyte components. Tobacco smoking has also been linked to the generation of carcinogenic radicals that increase the rate of damage through oxidative DNA by approximately 35 to 50% are a result of the urinaryremoval of 8-oxide, and that of 8-oxodG within the leukocytes by 20 to 50% (Friedman and Brandon, 2001, p. 1071).

The rate of generation of 8-oxodG is closely related to the internal sources of radicals. No studies had been done in a position to show that diet configurations, energy restraint, and antioxidant supplements can affect oxidative DNA alterations (Kgomotso and Chiu, 2008, p. 1458). However, there are suggestions that Brussels sprouts can minimize oxidative damage rate of DNA, and the quantity of 8-oxodG levels within the sperm cell can be controlled by vitamin C. Lowered intake of fats has also been linked to reduced oxidative damage to DNA within leukocytes. Diseases such as cystic fibroids, some autoimmune illnesses, compulsive hepatitis, and fanconianemia have been found to have the potential of increasing DNA damage rate through oxidation and at some point inadequate repair (Kgomotso and Chiu, 2008, p. 1459).

The studies done are perceived to be supportive of the actual human based DNA damage as a result of oxidation that is linked to mutagens and carcinogenesis processes. However, there is limited human research that fully confirms the link (Gilani et al., 2005, p. 987). A nested case-regulated mode of study can be applied to biobank matter to support DNA damage from oxidation as an independent cancer risk factor. Additionally, damage resulting from oxidation may be critical to the aging process, especially in relation to mitochondrial DNA, and the origin of inflammatory illnesses (Gilani et al., 2005, p.989).

Protein Fermentation Products and Colon Cancer

Colon cancer, which is linked to aberrant crypt foci (ACF) is promoted by thermalized casein as experimented on rats that have been introduced to azoxymethane (Smith and Caldwell, 2001, p.265). The condition is linked to the fermentation of proteins within the colon since casein thermolysis lowers the capacity of protein breakdown, heightens the protein quantities that reach the colon, hence fermentation leading to the generation of toxins that favor colonic carcinogenesis (Thermal heat processing, no date, p. 327). The fermentation process leads to the generation of products such as ammonia and a range of phenols. These products are toxic to mammalian cells and are a risk factor for cancer. Studies on rats indicate that a phenol called indole-3-ol that arises from the fermentation of tryptophan has been related to the onset of myelogenous leukemia in rats (Thermal heat processing, no date, p. 329). This test has been used to give a hypothetical explanation of the relationship between food and cancer of the colon. Cooked meat contains proteins that may increase fermentation of proteins within the colon. According to Thermal heat processing (no date, p. 330), the fermentation process is highest when protein is thermalized for about one hour, whereas promotion of ACF growth is highest when thermalysis takes a duration of about two hours and above.

However, not all protein products have shown the possibility of triggering colon carcinogenesis after thermolysis. For instance, thermalized proteins in eggs and soy have been shown to raise the levels of protein fermentation in the colon but the not promotion of carcinogenesis in the colon (Thermal heat processing, no date, p. 330).

Beneficial Effects of Processing

Food substances derived from plants containing toxic elements and anti-nutrients (cereals and legumes) have been shown to have helpful outcomes once they are processed. Their digestibility is enhanced by processes such as heating, drenching, fermentation, and germination (Millward et al., 2008, p. the 1580s). The processes destroy a number of inhibitive enzymes.

Food processing or cooking on digestibility of proteins create unique food structure, different from the food structure commonly obtained from traditional processing. Protein and starch have different sensitivities towards pressure, electric field strength, and temperature which impact their stability and the way how they cross-link and interact with other compounds present in the food (Tang et al., 2009, p. 990). Therefore, it is important to study how novel food processing affects the protein and starch digestibility and the bioaccessibility bioavailability of bio-actives in grain-based foods. This paper has covered processing development and also raises a question whether the effects of food processing can reduce food allergenicity such as gluten and improve the nutritional value(Schaafsma, 2000, p. 1866S). Understanding how protein alteration occurs under processing condition and how it affects how proteins are digested and starch and the bioavailability of bioactives will guide a new product development based on legume-based foods which contain the highest protein value.

Conclusion

In conclusion, therefore, anti-nutritional factors have been shown to affect the availability of amino acids and the ability to digest proteins. Some of the anti-nutrients such as D-amino acids are created through heating and chemical processes. Oxidation processes have been linked to the generation of free radicals that have been related to carcinogenesis (Tang et al., 2009, p. 987). Thermolysis of proteins increases their indigestibility thus reaching the colon and triggering the fermentation process that generates fermentation products that are linked to carcinogenesis in the colon (Smith and Caldwell, 2001, p.270). However, not all protein thermolysis is harmful. In some instances, it is beneficial as it destroys the inhibitive enzymes (Millward et al., 2008, p. 1581S).

References

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Kgomotso, T.; Chiu, F.; Ng, K (2008).Genistein- and daidzein7-O-(-D-glucuronic acid retain the ability to inhibit copper-mediated lipid oxidation of low-density lipoprotein. Molecular Nutrition & Food Research, 52, 1457-1466.

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Thermal heat processing effects on antinutrients, protein and starch digestibility of food legumes. Food Chemistry, 91(2), pp.327-331.

Schaafsma, G., 2000. The protein digestibility-corrected amino acid score. The Journal of Nutrition, 130(7), pp.1865S-1867S.

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Tang, J.E., Moore, D.R., Kujbida, G.W., Tarnopolsky, M.A. and Phillips, S.M., 2009. Ingestion of whey hydrolysate, casein, or soy protein isolate: effects on mixed muscle protein synthesis at rest and following resistance exercise in young men. Journal of Applied Physiology, 107(3), pp.987-992.