Dairy proteins, separation

Zydney, A.L., Protein separations using membrane filtration New opportunities for whey fractionation, Int. Dairy J., 8, 243, 1988. 

The separation of dairy proteins by CE has been generally carried out by CZE and has been exhaustively covered in several review papers, - - thus Table 30.8 only presents the key methodologies that offer the reader an overview of their most distinctive features. Basically, dairy protein analysis has been performed in whole milk for the simultaneous determination of caseins and whey proteins, or in fractions isolated from milk after casein precipitation. The first approach being used when the quantitative determination of the major proteins is required for the calculation of casein/whey protein ratios or for authentication purposes where an analysis of the whole protein profile is required. In both cases, accurate quantitative data must be derived. However, few studies have addressed the analysis of both groups of proteins in a single run by presenting quantitative data based on calibration curves constructed with analytical standards and good recovery of all proteins from milk samples. 

Finally, a third method was based on MEKC, where proteins were separated after complete denaturation with SDS and oL-dithiothreitol in uncoated capillaries at pH 9.5. Although the method had the advantage of being very rapid (separation completed in less than 90 s), it was not quantitative (Table 30.8). The second approach reported for the analysis of dairy proteins was the analysis of the whey fraction after casein precipitation. Unlike the methods described earher, separations were carried out in uncoated capillaries using polymeric additives, a high ionic strength, and high pH... 

Saz and Marina [148] published a comprehensive review on HPLC methods and their developments to characterize soybean proteins and to analyze soybean proteins in meals. In the case of soybean derived products, a number of papers dealing with cultivar identification [149,150], quantification of soybean proteins [151-154], detection of adulteration with bovine milk proteins [151,155-158], and characterization of commercial soybean products on the basis of their chromatographic protein profile [159,160] have been published in the last years. Other studies deal with the analysis of soybean proteins added to meat [161-165], dairy [151,165-167], and bakery products [156,163,168,169]. The same research group developed perfusion RP-HPLC methods for very rapid separation of maize proteins (3.4 min) and characterization of commercial maize products using multivariate analysis [170], and for the characterization of European and North American inbred and hybrid maize lines [171]. 

Bell, J. W. and Stone, W. K. 1979. Rapid separation of whey proteins by cellulose acetate electrophoresis. J. Dairy Sci. 62, 502-504. 

Raw milk is a unique agricultural commodity. It contains emulsified globular lipids and colloidally dispersed proteins that may be easily modified, concentrated, or separated in relatively pure form from lactose and various salts that are in true solution. With these physical-chemical properties, an array of milk products and dairy-derived functional food ingredients has been developed and manufactured. Some, like cheese, butter, and certain fermented dairy foods, were developed in antiquity. Other dairy foods, like nonfat dry milk, ice cream, casein, and whey derivatives, are relatively recent products of science and technology. This chapter describes and explains the composition of traditional milk products, as well as that of some of the more recently developed or modified milk products designed to be competitive in the modern food industry. 

During the nineteenth and early twentieth centuries, separation of the proteins was limited to casein and the classical lactalbumin and lacto-globulin fractions of the whey proteins. Subsequent work has resulted in the identification and characterization of numerous proteins from each of these fractions. A classification system of the known proteins in milk developed by the American Dairy Science Association s (ADSA) Committee on Milk Protein Nomenclature, Classification, and Methodology (Eigel et al 1984) is summarized and enlarged to include the minor proteins and enzymes in Table 3.1. 

Yaguchi, M. and Rose, D. 1971. Chromatographic separation of milk proteins A review. J. Dairy Sci. 54, 1725-1743. 

CM Hollar, AJR Law, DG Dagleish, RJ Brown. Separation of major casein fractions using cation-exchange fast protein liquid chromatography. J Dairy Sci 74 2403-2409, 1991. 

Milk of UF-standardized protein and total solids content enables the production of fermented dairy products of improved quality and characteristics compared with those produced from milk fortified with milk powder or evaporated milk [11]. Due to the similarity of the protein fractions in HMPP and those of skim milk and the virtual absence of lactose, Mistry and Hassan [134] suggested its utilization for the development of new dairy products and the improvement of existing ones. When these authors used HMPP to produce nonfat yogurt, they found that fortification level up to 5.6% protein can produce acceptable yogurt with smooth texture and firm body that did not exhibit whey separation even without the addition of stabilizers. They noted, however, that >5.6% protein concentration, the yogurt becomes excessively firm and has a grainy texture and flat flavor. 

Proteins in homogenized dairy products Symmetrical Separation of whey proteins from fat globules fractionation of whey proteins and casein micelles effect of carrier ionic strength, cross-flow rate, pH, and membrane type on retention and size distribution of micelles [M. A. Jussila, G. Yohannes, and M.-L. Riekkola, J. Microcol. Separ. 9 601-609 (1997)]... 

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