Food protein methods

Spanhaak, S. and Penninks, A.H. (1999) An oral sensitization model in Brown Norway rats to screen for potential allergenicity of food proteins. Methods (San Diego, Calif), 19, 78-82. 

A method using transglutaminase for reducing the allergerricity of some food proteins and/or peptides has been developed as well, hf j-Casein (23 kDa) was treated with transglutaminase at 25°C for 20 h in water to manufactrrre cross-linked casein (approx. 90 kDa), which was less allergettic. 

Human perception of flavor occurs from the combined sensory responses elicited by the proteins, lipids, carbohydrates, and Maillard reaction products in the food. Proteins Chapters 6, 10, 11, 12) and their constituents and sugars Chapter 12) are the primary effects of taste, whereas the lipids Chapters 5, 9) and Maillard products Chapter 4) effect primarily the sense of smell (olfaction). Therefore, when studying a particular food or when designing a new food, it is important to understand the structure-activity relationship of all the variables in the food. To this end, several powerful multivariate statistical techniques have been developed such as factor analysis Chapter 6) and partial least squares regression analysis Chapter 7), to relate a set of independent or "causative" variables to a set of dependent or "effect" variables. Statistical results obtained via these methods are valuable, since they will permit the food... 

Soy protein is a low-cost food protein with good nutritional value, but its uses in foods are limited because of inferior functional properties as compared to those of commonly used animal proteins such as casein and albumin (1.2). Therefore, modifications are often required to make soy protein more suitable for food use. Improved functional properties, particularly in the pH range of 3 to 7 where most food systems belong, have been achieved by non-enzymatic methods, including succinylation (3-5), deamidation (6.7), and phosphorylation (8.9). 

Values for a test protein will be lower than for the reference protein. The reliability of results for chemical scoring methods depends upon the accuracy of the amino acid determinations that form the basis for these assays. Chemical scoring and animal bioassays tend to provide similar relative rankings of protein quality however, the actual values may be different. Chemical scoring methods should not replace a bioassay for testing the quality of a food protein for which there is very little nutritional information. 

Li-Chan, E.C. 1998. Methods to monitor process-induced changes in food proteins. An overview. Adv. Exp. Med. Biol. 434 5-23. 

Using contact angle (see Basic Protocol 4), the quantitative determination on the basis of the Lifshiz-van der Waals and electron donor-acceptor of Lewis acid-base interactions contributing to surface tension was extended to proteins (van Oss et ah, 1981). Despite its relative simplicity, the method has not gained popularity in the application to food proteins directly, probably because of the lack of similarity with proteins in solutions as this method uses a semi-dried form of proteins. However, investigation of the quality of packaging material, such as permeation and absorption, may... 

Some basic food analytical methods such as determination of °brix, pH, titratable acidity, total proteins and total lipids are basic to food analysis and grounded in procedures which have had wide-spread acceptance for a long time. Others such as analysis of cell-wall polysaccharides, analysis of aroma volatiles, and compressive measurement of solids and semi-solids, require use of advanced chemical and physical methods and sophisticated instrumentation. In organizing the Handbook of Food Analytical Chemistry we chose to categorize on a disciplinary rather than a commodity basis. Included are chapters on water, proteins, enzymes, lipids, carbohydrates, colors, flavors texture/ rheology and bioactive food components. We have made an effort to select methods that are applicable to all commodities. However, it is impossible to address the unique and special criteria required for analysis of all commodities and all processed forms. There are several professional and trade organizations which focus on their specific commodities, e.g., cereals, wines, lipids, fisheries, and meats. Their methods manuals and professional journals should be consulted, particularly for specialized, commodity-specific analyses. 

Motivation for protein determination Applications in food analysis Method of HPLC Refs. 

Bertrand-Harb, C., Chobert, J.-M., Dufour, E., and Haertle, T. 1991. Esterification of food proteins characterisation of the derivatives by a colorimetric method and by electrophoresis. Sci. Aliments 11, 641-652. 

Shih, F.F. 1992. Modification of food proteins by non-enzymatic methods In Biochemistry of Food Proteins (B.J.F. Hudson ed.), pp. 235-270. Elsevier Applied Science Publishers, London. 

Recio, I., Floris, R., and Visser, S. 2000. Bioactive peptides from food proteins a new isolation method. Agro-Food-Ind. Hi-Tech 2, 9—11. 

Chemical Reactions Analytical Methods. During severe heat treatments of food proteins, chemical reactions occur between the e-amino group of lysine and the carboxamide group of the glutaminyl and aspara-ginyl residues (75). 

Recently a simplified process was developed for incorporating l-methionine directly into soy proteins during the papain-catalyzed hydrolysis (21). The covalent attachment of the amino acid requires a very high concentration of protein and occurs through the formation of an acyl-enzyme intermediate and its subsequent aminolysis by the methionine ester added in the medium. From a practical point of view, the main advantage of enzymatic incorporation of amino acids into food proteins, in comparison with chemical methods, probably lies in the fact that racemic amino acid esters such as D,L-methionine ethyl ester can be used since just the L-form of the racemate is used by the stereospecific proteases. On the other hand, papain-catalyzed polymerization of L-methio-nine, which may occur at low protein concentration (39), will result in a loss of methionine because of the formation of insoluble polyamino acid chains greater than 7 units long. 

Although the above discussion might indicate that the attachment of amino acids to food proteins under commercial conditions is only remotely possible in the foreseeable future, many of the questions raised can be answered through carefully planned research. Some of the modifications may be useful, if not alone, perhaps in conjunction with enzymological methods. Therefore we encourage continued research in this potentially important area. 

Determination of the Amino Acids. Richard J. Block. 91 pp. Burgess Publishing Co., Minneapolis, Minn., 1938. Revised ed. with Diana Bolling. 58 pp. 1941. Amino Acid Composition of Proteins and Foods. Analytical Methods and Results. 

There are large resources of potential food proteins (oilseed, yeast, leaf) which are presently unexploited. With the application of innovative scientific and technological methods these can become significant sources of food protein. In developing ingredient protein from plant sources, research emphasis must include studies to determine the physicochemical or functional properties of these proteins. 

Reactions in proteins and other nitrogenous compounds catalyzed by endogenous enzymes are responsible for desirable and undesirable sensory attributes of foods — color, flavor, and texture — as well as for the development of compounds that are nutritionally beneficial or have detrimental effects on human health. The use of added enzymes or enzyme sources is also an essential part of many traditional methods of food processing. Since the conditions of enzymatic reactions are much milder than those applied in chemical treatments, different added enzymes are being used to an increasing extent to modify the functional properties of food proteins. 

R702 P. Minkiewicz, J. Dziuba and D. Nalecz, Current Methods of Separation and Structure Determination of Peptides and Food Proteins , Przem. Spozyw., 2000, 54, 34... 

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