Caseinates functional properties

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). 

In vitro, the enzyme is able to catalyze crosslinking of whey proteins, soy proteins, wheat proteins, beef myosin, casein, and crude actomyosin (which is refined from mechanically deboned meat), improving functional properties such as the texture of food products [49-53], Bonds formed by transglutaminase exhibit a high resistance to proteolytic degradation [54],... 

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). 

Modler, H.W. (1985). Functional properties of nonfat dairy ingredients — a review. Modification of products containing casein. Journal of Dairy Science, 68, 2195-2205. 

Q The most detailed studies were reported by Hermansson and Akesson ( , 41) and Hermansson (42) in which the properties of a soy isolate, caseinate, WPC, and model test systems of additive and lean beef or pork were studied. Solubility, swelling, and viscosity (properties reviewed as related to water absorption) were correlated with moisture loss in the raw systems. In cooked systems, the best predictability of meat texture as affected by additive was a statistical model that included the functional properties of swelling and gel strength of protein additive dispersions. 

It is essential to consider the physico-chemical properties of each WPC and casein product in order to effectively evaluate their emulsification properties. Otherwise, results merely indicate the previous processing conditions rather than the inherent functional properties for these various products. Those processing treatments that promote protein denaturatlon, protein-protein Interaction via disulfide interchange, enzymatic modification and other basic alterations in the physico-chemical properties of the proteins will often result in protein products with unsatisfactory emulsification properties, since they would lack the ability to unfold at the emulsion interface and thus would be unable to function. It is recommended that those factors normally considered for production of protein products to be used in foam formation and foam stabilization be considered also, since both phenomena possess similar physico-chemical and functionality requirements (30,31). 

Casein may be coagulated and recovered as rennet casein by treatment of milk with selected proteinases (rennets). However, one of the caseins, K-casein, is hydrolysed during renneting and therefore the properties of rennet casein differ fundamentally from those of acid casein. Rennet casein, which contains the colloidal calcium phosphate of milk, is insoluble in water at pH 7 but can be dissolved by adding calcium sequestering agents, usually citrates or polyphosphates. It has desirable functional properties for certain food applications, e.g. in the production of cheese analogues. 

Enzymatic hydrolysis of food proteins yields peptides that are of great interest to the food industry and are utilized for various purposes, e.g., improving the functional properties of foods, parenteral feeding (casein hydrolyzates), or milk protein substitutes in cases of intolerance. 

Enzymatic phosphorylation by phosphorylases and phosphatases produces phosphoesters such as phosphoserine and phosphothreonine. Chemical phosphorylation of proteins changes their functional properties, improving them sometimes (Yoshikawa et al., 1981 Hirotsuka et al., 1984 Huang and Kinsella, 1986 Chobert etal, 1989 Matheis, 1991). However, the properties of the phosphorylated proteins depend entirely on the degree of denaturation and substitution defined by the reaction conditions and the protein (Medina etal, 1992 Sitohy etal, 1994). Casein was phosphorylated by the commonly used methods, characterized by use of excessive amounts of phosphorus oxychloride and with important additions of concentrated inorganic bases (Matheis et al, 1983 Medina et al, 1992). Thus, obtained phosphorylated caseins were highly cross-linked and partially insoluble and difficult to characterize. Hence, there arose a need to produce monomeric over-phosphorylated caseins more suitable for use and for study of their... 

The whey produced during cheese and casein manufacturing contains approximately 20% of all milk proteins. It represents a rich and varied mixture of secreted proteins with wide-ranging chemical, physical and functional properties (Smithers et al., 1996). Due to their beneficial functional properties, whey proteins are used as ingredients in many industrial food products (Cheftel and Lorient, 1982). According to Kinsella and Whitehead (1989), functional properties of foods can be explained by the relation of the intrinsic properties of the proteins (amino acid composition and disposition, flexibility, net charge, molecular size, conformation, hydrophobicity, etc.), and various extrinsic factors (method of preparation and storage, temperature, pH, modification process, etc.). 

Haque, Z.U. and Mozaffar, Z. 1992. Casein hydrolysate. II. Functional properties of peptides. Food Hydrocoil. 5, 559-571. 

Slattery, H. and FitzGerald, R.J. 1998. Functional properties and bitterness of sodium caseinate hydrolysates prepared with a Bacillus proteinase. J. Food Sci. 63, 418-422. 

Limiting essential amino acids covalently attached to proteins by using activated amino acid derivatives can improve the nutritional quality and change the functional properties of proteins. The best chemical methods for incorporating amino acids into water-soluble proteins involve using car-bodiimides, N-hydroxysuccinimide esters of acylated amino acids, or N-carboxy-a-amino acid anhydrides. The last two methods can give up to 75% incorporation of the amount of amino acid derivative used. With the anhydride method, as many as 50 residues of methionine have been linked to the 12 lysine residues of casein. The newly formed peptide and isopeptide bonds are hydrolyzed readily by intestinal aminopeptidase, making the added amino acids and the lysine from the protein available nutritionally. 

Some physical and functional properties of casein modified by the covalent attachment of amino acids are given in Table IX. Despite extensive modification, the relative viscosities of 2% solutions of the modified proteins did not change significantly, with the exception of aspartyl casein which was more viscous. There was some decrease in the solubilities of aspartyl casein and tryptophyl casein as compared with the casein control. It is anticipated that adding some 11.4 tryptophyl residues per mole of casein would decrease the aqueous solubility of the modified protein. However the results with aspartyl casein are unexpected. The changes in viscosity, solubility, and fluorescence indicate that aspartyl casein is likely to be a more extended molecule than the casein control. There was a marked decrease in the fluorescence of aspartyl casein and tryptophyl casein (see Table IX). The ratios of the fluorescences of acetylmethionyl casein to methionyl casein and t-BOC-tryptophyl casein to tryptophan casein were 1.20 and 2.01, respectively, indicating the major effects that these acyl groups have on the structure of the casein. 

Canton, M., Mulvihill, D.M. 1982. Functional properties of commercial and chemically modified caseins and caseinates. Irish J. Food Sci. Technol. 6, 107 (abstract). 

Proteolysis in cheese has been studied extensively and reviewed (Fox and Wallace 1997 McSweeney, 2004 Upadhyay et al., 2004). It contributes directly to flavor, via the formation of peptides and free amino acids (FAA), and indirectly via the catabolism of free amino acids to various compounds including amines, acids, thiols (Curtin and McSweeney, 2004). Proteolysis directly affects the level of intact casein, which is a major determinant of the fracture and functional properties, and of cheese texture (de Jong, 1978b Creamer and Olson, 1982 Creamer et al., 1982 Guinee, 2003 Brown et al., 2003). 

Chemical derivatization of proteins to modify functional properties has received limited consideration. Cationic derivatives of food proteins are routinely used (e.g. sodium soy isolates and sodium and calcium caseinates) to improve wettability, dispersibility and handling properties of these proteins (27). 

This paper draws heavily upon the "Nomenclature Committee Report" ( 1) as well as several recent comprehensive reports that have considered the primary structure and conformation of the casein monomer subunits and how they are assembled into submicel-lar aggregates and casein micelles (2, 3). These basic relationships were utilized to develop additional projections relating to the conformation and functional properties of the major milk proteins, e.g., commercial caseinates and whey protein concentrates in food applications. 

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