Dairy proteins

Extrusion Texturized Dairy Proteins Processing and Application... 

Dairy proteins are rich in nutrients and occupy a unique place of importance in food and human nutrition because of their wide acceptance in the world. Milk proteins are important in the diet because of the many health benefits associated with their consumption. The proteins have long been recognized as natural sources of health enhancing bioactive peptides because of their stmctural and physicochemical components as recently reviewed by Livney (2010). 

There is a continuing interest to improve and extend the fimctional properties range of dairy proteins to provide both health benefits and their characteristic physical behaviors under different temperature, moisture, and pH conditions so that they may be included in foods that ordinarily do not contain them. One such research area is the extrusion texturization of whey proteins, which have resulted in dairy proteins with new characteristics imparted by a controlled texturization process, depending on the application desired (Hale et al., 2002 Manoi and Rizvi, 2008 Onwulata, 2009 Onwulata et al., 1998). Protein texturization is a two-step process that involves, first, the unfolding of the globular structure (denaturation) and, second, the alignments of the partially unfolded structures in the direction of mass flow in the extruder. The surface characteristics are imparted at the extruder die as the molten mass exits (Onwulata et al., 2003a). 

FIGURE 5.6 Solubility of texturized dairy protein products extruded at different temperatures, 25 (control), 50, 75, and 100 C Nonfat dried milk (NDM) whey protein concentrate (WPC80), containing 80% protein and whey protein isolate (WPl), containing 95% protein (Onwulata et at, 2003a). 

Extrusion texturization minimizes the water binding capacity of dairy protein products, in decreasing order, WPI > WPC > NDM, as temperature increases, making them interact better with starch. 

For example, the consistency of the extruded dairy proteins can range from rigid (2500 N) to soft (3 N). Extruding above 60 °C resulted in significantly increased peak force for WPC (138-2500 N) and minimal increase in peak force for WPI (3-147.1 N). NDM was nof fully fexfurized fhe presence of lacfose interfered with the texturization. The solubility of WPI producfs ranged from 72% to 93%. 

Coextrusion is the process of extruding two or more materials simultaneously or in tandem. It allows a combination of an ingredient such as wheat flour, which is inexpensive and easily enriched with vitamins and minerals, with dairy protein, which provides functionality and texture. For example, an early coextrusion of wheat flour and rennet casein was performed by van de Voort et al. (1984), who obtained products with varying characteristics depending on process parameters. 

Dairy proteins can be used to boost the protein content of sfarch-based puffed snacks made from cornmeal fhey bind wafer and form doughy pastes with the starch, but not the non-TWPs. A wide possibility exists for creating new foods wifh fexfurized dairy proteins due to the availability of an extensive range of achievable sfates (Onwulafa et ah, 2010). 

It is demonstrated here that extrusion is an effective tool for texturing whey proteins to create new functions for dairy proteins and that thermally denatured WPl is a unique ingredient that can be used in large amounts in nontraditional applications for non-TWPl. This review covers the use of extrusion texturized dairy ingredients in foods however, there are other examples of fhe successful use of this technique along with the product, TWPl in different types of nonfood applications, such as in biodegradable films, and bioplastics. 

Onwulata, C. I. (2010). Texturization of dairy proteins for food applications. Food Eng. Ingred. 35, 8-11. 

Onwulata, C. I., Konstance, R. P., and Tomasula, P. M. (2002). Viscous properties of micro-particulated dairy proteins and sucrose. /. Dairy Sci. 85,1677-1683. 

The literature is replete with methods to measure protein functional properties. For example, Kneifel et al. (1991) listed about 70 published methods to measure the water-holding ability of dairy proteins. Table B5.1.1, Table B5.1.2, and Table B5.1.3 list some common tests used to evaluate the functional properties of proteins. The methods in these tables should serve as examples only. Selection of the proper test to evaluate a particular functional property is difficult. A functional property test must meet the needs of the user and answer the question(s)... 

The dye 4, 6-Diamidino-2-PhenyIindole (DAPI) in 0.001%W/V aqueous solution can be used directly on smears, ciyosections and embedded specimens to locate and count culture bacteria, without regard to their viability, in cheese and other cultured products. The dye reacts with nucleic acids by intercalation. Excitation at 360nm is best for this dye. It is worth noting two other facts about its use. DAPI cross reacts with dairy proteins, but the color of the protein-dye complex is different from that of the nucleic acid-dye complex (the latter is a steely blue/white) and so the two reactions may be discriminated. The dye also may take up to 15 minutes to enter bacterial cells, particularly spores, before fluorescence is observed. An alternative nucleic acid dye, Ethidium Bromide, has less contrast between the fluorescence induced in cells and the fluorescence of cross-reacting dairy proteins. It should be tried in other products such as meats if DAPI is not successful. 

In order to evaluate an individual s exposure to chemical mixtures, it was necessary to determine how frequently pesticide and industrial chemicals were found in each food product. The results of this determination are discussed for the basic food categories (i.e., dairy, protein, vegetable, fruit, and grain) as well as for the mixed food and child/infant food categories. 

The pesticides and industrial chemicals found in child and infant products are given in Exhibit 13. In general, the type and distribution of pesticides and industrial chemicals in child/infant products are somewhat similar to the basic food categories (i.e., dairy, protein, fruit, grain, and vegetable), but their concentrations are significantly different. On average, 45 percent of the child/infant products contain multiple contaminants as well as banned or discontinued pesticides. 

Functional properties of proteins are closely related to their size, structural conformation, and level and distribution of ionic charges. Chemical treatments, which could cause alteration of these properties, include reactions that either introduce a new functional group to the protein or remove a component part from the protein. Consequently, reactions such as acylation, phosphorylation, esterification, glycation, limited hydrolysis, and deamidation have been used to impart improved functional properties to the dairy proteins. 

This review concerns some chemical, enzymatic and genetic methods that modify dairy proteins with an emphasis on current developments. 

To improve their functional and physico-chemical properties, dairy proteins have been modified by several methods (Haertle and Chobert, 1999), such as phosphorylation (Sitohy et al., 1995c), esterification (Chobert et al., 1995 Sitohy et al., 2001c), alkylation (Kitabatake et al., 1985), and reductive amidation (Mattarella et al., 1983) (see Section n.A., B.). However, most of these methods, using toxic chemicals, cannot be used in food processing. 

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