Casein, gluten

Vegetable caseins,—Gluten casein, legumin, couglutin. 

Dynamic mechanical thermal analysis (DMTA or DMA) has been used to analyze glass transitions in foods (cheese, casein, gluten, soy isolates, starches and chocolate) [131,132]. 7 g is measured as the middlepoint of the change in elastic (E ) or loss (E") moduluses, as well as the loss peak in tan 5, as a function of temperature. The modulus drop at 7g encompasses two or three orders of magnitude the DTMA determination of 7 g is therefore much easier than by DSC, since the relevant heat capacity change at 7g can be very small [132]. 

Protein-Based Substitutes. Several plant and animal-based proteins have been used in processed meat products to increase yields, reduce reformulation costs, enhance specific functional properties, and decrease fat content. Examples of these protein additives are wheat flour, wheat gluten, soy flour, soy protein concentrate, soy protein isolate, textured soy protein, cottonseed flour, oat flour, com germ meal, nonfat dry milk, caseinates, whey proteins, surimi, blood plasma, and egg proteins. Most of these protein ingredients can be included in cooked sausages with a maximum level allowed up to 3.5% of the formulation, except soy protein isolate and caseinates are restricted to 2% (44). 

Nitrogen sources include proteins, such as casein, zein, lactalbumin protein hydrolyzates such proteoses, peptones, peptides, and commercially available materials, such as N-Z Amine which is understood to be a casein hydrolyzate also corn steep liquor, soybean meal, gluten, cottonseed meal, fish meal, meat extracts, stick liquor, liver cake, yeast extracts and distillers solubles amino acids, urea, ammonium and nitrate salts. Such inorganic elements as sodium, potassium, calcium and magnesium and chlorides, sulfates, phosphates and combinations of these anions and cations in the form of mineral salts may be advantageously used in the fermentation. 

Seven diets were constructed from purified natural ingredients obtained from either C3 (beet sugar, rice starch, cottonseed oil, wood cellulose, Australian Cohuna brand casein, soy protein or wheat gluten for protein) or C4 foodwebs (cane sugar, corn starch, com oil, processed corn bran for fiber, Kenya casein for protein) supplemented with appropriate amounts of vitamins and minerals (Ambrose and Norr 1993 Table 3a). The amino acid compositions of wheat gluten and soy protein differ significantly from that of casein (Ambrose and Norr 1993). 

These products are made by adding protein to flour. While whey protein, soya protein, casein and yeast can be used the protein normally employed is pure vital wheat gluten. 

Friedman (21) studied the effect of pH on the amino acid composition of wheat gluten. At pH 10.6 and above (65 C, 3 hours) no cystine was present. LAL increased with pH above 10.6. Lysine decreased over the same range of pH s, while serine and threonine contents dropped sharply at pH 13.9. Friedman concluded that cystine is most sensitive to alkali and that LAL will form most readily if lysine residues are in proximity to the dehydroalanine formed from cystine. Thus, he explained that different steric considerations may explain the different susceptibilities of wheat gluten, casein, and lactalbumin to LAL formation. 

Amino acid storage Seed proteins (e.g., gluten), milk proteins (e.g., casein)... 

Ingredients. All ingredients were obtained commercially along with compositional information and consisted of corn starch (National Starch, Bridgewater, NJ), whey protein concentrate (WPC) and sodium caseinate (SC) (Leprino Foods, Denver, CO), defatted soy flour (DSF) (Archer Daniels Midland, Decatur, IL), soy protein concentrate (SPC) (Central Soya Company, Fort Wayne, IN), and gluten (G) (Ogilvie Mills Ltd., Montreal, Canada). 

It is interesting to see that proteins with high Q-values above 1400 as e.g. soybean protein, casein wheat gluten, potato protein, Zein are the "parents" of bitter peptides, whereas no bitter peptides have been isolated from hydrolysates prepared from collagen or gelatin, proteins with Q-values below 1300. 

Our results have been recapitulated with other proteins of varying nutritional value to S. exigua and H. zea they include soy protein, tomato foliar protein, corn gluten and zein. In all cases, more than 2.5% dietary protein was required to alleviate antinutritional effects, because these proteins are less nutritious than casein (Table III). The ability of a protein to alleviate the toxicity of o-quinones is proportional to its nutritional value to the insect (Table III). The proteins ability to function as an alkylatable sink (alleviation of antinutritive effects) is correlated with the relative amounts of alkylatable amino acids (e.g., lysine, cysteine, histidine, methionine Felton and Duffey, unpublished data). 

The percentage of D-enanticmers relative to the total amount of the amino acid residue can be calculated by the relation (D/DfL) x 100. D-Aspartic acid accounts for 30% of that residue (which is thus 60% racemized) in treated casein, Pranine-D, and wheat gluten. In these three proteins, 22-30% of the phenylalanine (an essential amino acid) is the D-enanticmer, and in wheat gluten, 26% of glutamic acid has been converted to the D-form. 

The rates within each protein were then standardized relative to that of leucine. The order of relative racemization rates is presented in Table II. Relative rates are very similar among the various proteins except for aspartic acid and glutamic acid in wheat gluten. This situation is discussed below. (The relative rate constants estimated for the second region of the casein curves in Figure 2, using the 3-hour and 24-hour points, is k(asp) k(p>he) k(glu) k(ala) k(leu) = 4.0 3.0 2.5 2.5 1.0.)... 

The pH dependence of the raeemization rate of aspartic acid in casein was also investigated. The results are plotted in Figure 3. Raeemization rates are estimated fron the log conversion of the D/L ratios. The pH of the NaCH buffer at 65° was calculated fron the temperature variation of the pK of water (32). The pH values of the borate buffers at 65° were calculated using the temperature data of Bates (33). The solid line represents rates which are first order with respect to hydroxide concentration. This line is a reasonable fit to the data points above pH 10. Further experiments are in progress with other proteins in order to identify the lowest CH concentrations that induce first-order raeemization kinetics. If the critical base concentrations for racemiza-tion correspond with the different responses of the four proteins (see Tables I and III), one may expect k(rac) for Promine-D to become first order at lower CH concentration than casein, while that of wheat gluten should be about the same as for casein. Lactalbumin may have the highest CH concentration tolerance. 

Partial hydrolysis of proteins using acid, alkali or enzymes is commonly employed to improve functionality and usefulness of novel proteins. Acid hydrolysis is the most common method for preparing hydrolysates of soy, zein, casein, yeast and gluten. Hydrolysates are used in formulated foods, soups, sauces, gravies, canned meats, and beverages as flavorants and thickeners (2,3,6). Alkaline treatments have been employed to solubilize and facilitate protein extraction from soy, single cells, and leaves. 

In previous papers, we have (a) reviewed elimination reactions of disulfide bonds in amino acids, peptides, and proteins under the influence of alkali (5) (b) analyzed factors that may operate during alkali-induced amino acid crosslinking and its prevention (6) (c) demonstrated inhibitory effects of certain amino acids and inorganic anions on lysinoalanine formation during alkali treatment of casein, soy protein, wheat gluten, and wool and on lanthionine formation in wool ( 7, 9) (d) demonstrated that... 

Commercial casein was obtained from International Casein Corporation, San Francisco, California commercial wheat gluten and lactalbumin from United States Biochemical Corporation, Cleveland, Ohio. 

The amino acid composition of alkali-treated casein, lactal-bumin, and wheat gluten are given in Tables I-III. The results show that the following amino acids are destroyed to various extents under basic conditions threonine, serine, cystine, lysine, and arginine, and possibly also tyrosine and histidine. The losses of these amino acids is accompanied by the appearance of lysinoalanine and other ninhydrin-positive compounds. 

Comparison of lysinoalanine values for wheat gluten, casein and lactalbumin treated at various pH s shows large differences in the amounts of lysinoalanine formed in the three proteins. 

For example, the respective values at pH 10.6 are 0.262, 0.494, and 1.04 mole per cent (ratio of about 1 2 4) at pH 11.2 the values are 0.420, 0.780, and 1.32 mole per cent and at pH 12.5 (pH of 1% protein solution in 0.IN NaOH), the respective values are 0.762, 0.780, and 2.62 mole per cent. (Note that the value of casein approaches that of gluten at this pH). The observed differences in lysinoalanine content of the three proteins at different pH values are not surprising since the amino acid composition, sequence, protein conformation, molecular weights of protein chains, initial formation of intra- versus intermolecular crosslinks may all influence the chemical reactivity of a particular protein with alkali. Therefore, it is not surprising to find differences in lysinoalanine content in different proteins treated under similar conditions. These observations could have practical benefits since, for example, the lower lysinoalanine content of casein compared to lactalbumin treated under the same conditions suggests that casein is preferable to lactalbumin in foods requiring alkali-treatment. 

Lysinoalanine formation in casein, lactalbumin, and wheat gluten was measured at 65°C at various pH s for 3 hours. Factors that control the extent of formation of the unnatural amino acid lysinoalanine during food processing and thus the degree of crosslinking in structurally different proteins are discussed. 

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