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Rapid Separation and Quantification of Major Caseins and Whey Proteins of Bovine Milk by Polyacrylamide Gel Electrophoresis

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      Abstract

      A rapid polyacrylamide gel electrophoretic method was developed for separating and quantifying major proteins in casein and whey protein fractions of bovine milk. For casein separation, best results were achieved by an 8% polyacrylamide gel containing 4 M urea and a top layer of large pore sample gel; for whey protein the most satisfactory separation was with 12% polyacrylamide gel in the absence of urea and a large pore gel. Electrophoretic conditions for separation of whey protein were also applicable for identifying genetic variants of β-lactoglobulin. Densitometric tracings were used to resolve and quantify protein peaks from stained bands in the gels. Casein was resolved into three major fractions with relative proportions of 50:30:15 for αs1- and αs2-casein, β-casein, and κ-casein. Whey protein was resolved into four major fractions with relative proportions of approximately 60:20:7:13 for β-lactoglobulin, α-lactalbumin, serum albumin, and immunoglobulin.

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