Protein isolation, from foods

Medina and Phillips (36) analyzed the peptide pattern obtained by the enzymatic hydrolysis of proteins isolated from beef, pork, chicken, and soybean sequentially, using TLC and HPLC to identify the proteins. The analysis was performed using RP-HPLC on a /zBondapak C8 column under isocratic conditions using triethylamine phosphate buffer (0.0833 M, pH 3) as solvent. Figure 5 depicts the peptide pattern of fraction IV isolated from beef, soybean, chicken, and pork by TLC. Identification of the different foods was accomplished by applying discriminant analysis to the peptide pattern. 

Krause, J., Schultz, M., and Dudek, S. 2002. Effect of extraction conditions on composition, surface activity and rheological properties of protein isolates from flaxseed (Linum usitativissimum L). J. Sci. Food Agric. 82, 970-976. 

Rawate, P.D. and Hill, R.M., Extraction of a high-protein isolate from Jerusalem artichoke (Helianthus tuberosus) tops and evaluation of its nutritional potential, J. Agric. Food Chem., 33, 29-31, 1985. 

Ou, S., Wang, Y., Tang, S., Huang, C., and Jackson, M.G. (2005). Role of ferulic acid in preparing edible films from soy protein isolate. J. Food Eng. 70, 205 210. 

Peng, Z., Pocock, K.F., Waters, E.J., Francis, I.L., WiUiams, R.J. (1997). Taste properties of grape (Vitis vinifera) pathogenesis-related proteins isolated from wine. J. Agric. Food Chem., 45, 4639-4643... 

Emefu, E.E., Ojimelukwe, P.C., and Mbata, G.N. 1992. Effect of insect infestation on the proximate composition and functional properties of flour samples and protein isolates from bambara groundnut and cowpea. J. Food Sci. Technol. 29, 174-176. 

Beermann, C., Euler, M., Herzberg, J., Stahl, B., 2009. Anti-oxidative capacity of enzymatically released peptides from soybean protein isolate. European Food Research and Technology 229, 637-644. 

Kodagoda, L. P, Yeung, C. Y., Nakai, S. and Powrie, W. D. 1973. Preparation of protein isolates from rapeseed flour. Can. Inst. Food Set Technol. J. 6 135-138. 

Ath 1, Gibbs BF, Okoniewska MK, Konishi Y, Dumas F 1993. Identification and characterization of phaseohn polypeptides in a crystalline protein isolated from white kidney beans (Phaseolus vulgaris). J Agric Food Chem 41 1830-1834. 

Products prepared from soy protein products and resembling chicken, ham, frankfurters, and bacon are available commercially. Soy protein isolates are used in place of milk proteins or sodium caseinate in products such as coffee creamers, whipped toppings, yogurt, and infant formulas (see Dairy substitutes). Soy protein products also are used in snacks and in baked foods. 

Riboflavin was first isolated from whey in 1879 by Blyth, and the structure was determined by Kuhn and coworkers in 1933. For the structure determination, this group isolated 30 mg of pure riboflavin from the whites of about 10,000 eggs. The discovery of the actions of riboflavin in biological systems arose from the work of Otto Warburg in Germany and Hugo Theorell in Sweden, both of whom identified yellow substances bound to a yeast enzyme involved in the oxidation of pyridine nucleotides. Theorell showed that riboflavin 5 -phosphate was the source of the yellow color in this old yellow enzyme. By 1938, Warburg had identified FAD, the second common form of riboflavin, as the coenzyme in D-amino acid oxidase, another yellow protein. Riboflavin deficiencies are not at all common. Humans require only about 2 mg per day, and the vitamin is prevalent in many foods. This vitamin... 

Water birds have not been shown to be directly affected by acidification. However, the prey of waterbirds may be of concern as these lower food-chain organisms may have elevated levels of toxic metals related to acidification of their habitat. Moreover, most water birds rely on some component of the aquatic food-chain for their high protein diet. Invertebrates that normally supply caJcium to egg-laying birds or their growing chicks are among the first to disappear as lakes acidify. As these food sources are reduced or eliminated due to acidification, bird habitat is reduced and reproductive rate of the birds is affected. The Common Loon is able to raise fewer chicks, or none at all, on acidic lakes where fish populations are reduced 37 and 5S). However, in some isolated cases, food supplies can be increased when competitive species are eliminated (e.g.. Common Goldeneye ducks can better exploit insects as food when competition from fish is eliminated). The collective influences of acidification are difficult to quantify on a specific area basis but for species that rely on a healthy aquatic ecosystem to breed, acidification remains a continuing threat in thousands of lakes across eastern North America 14). 

Presently about 20 different mutagenic and/or carcinogenic heterocyclic amines (HAs) have been isolated from various heat-processed foods. One class of these HAs is formed by pyrolysis of proteins or some amino acids. These HAs are amino-carbolines (Figure 13.7), and have been identified in grilled, broiled, baked, and fried meat and fish products, in meat sauces and bouillons, as well as in pyrolyzed proteins, glutamate, lysine, phenylalanine, tryptophan, ornithine, and creatine. 

Dialysis and ultraflltration have been largely applied to isolate and fractionate food proteins and peptides. To isolate the protein fraction from wine and must samples, different authors used dialysis followed by lyophilization to concentrate the dialyzed samples [106,108,109], Depending on the application, membrane of different material, filtration surface and cut-off, able to fractionate the molecules in function of their molecular size, can be used to remove either proteins and other macromolecules or amino acids and small peptides. 

The flavor enhancer monosodium glutamate (MSG) is currently used in virtually every type of savory prepared-food. Unfortunately, MSG has several deleterious side effects on a large proportion of the population. Fortunately, a naturally occurring peptide isolated from a muscle food (beef) can serve not only as a potential replacement for MSG but also as a nutritional adjuvant. The peptide, called BMP or beefy meaty peptide, acts as a flavor enhancer and is found to occur naturally in beef Chapter 6). Research on BMP suggest that it is not only non-allergenic but, by virtue of its protein composition, is a nutritionally sound replacement for MSG. 

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