Electrophoretic and biochemical comparison of casein and whey protein from porcine colostrum and milk.

Porcine colostrum casein contained at least one major polypeptide band in both acid gel and sodium dodecyl sulfate gel electrophoresis that did not appear in patterns of casein prepared from porcine milk. In sodium dodecyl sulfate gel patterns, this polypeptide possessed a molecular weight of 62,000 and stained positively with "Stains-all" but not with periodic acid-Schiff reagent. Several minor caseins that appeared in acid and alkaline gel patterns from colostrum could not be detected in casein prepared from milk. Seven minor polypeptides in sodium dodecyl sulfate gel patterns of whey proteins prepared from porcine colostrum could not be detected in milk. Identical acid and alkaline gel patterns were obtained for whey proteins prepared from colostrum and milk. Only the sodium dodecyl sulfate gel electrophoretic pattern of casein prepared from milk, and possibly the alkaline gel electrophoretic pattern of whey protein prepared from milk, contained polypeptides not in patterns from colostrum. Total phosphorus contents of colostrum and milk casein were 2.96% and 3.78%. Casein prepared from porcine colostrum contained almost twice as much hexosamine and slightly elevated N-acetylneuraminic acid as casein prepared from milk. Hexose content was nearly equivalent. Whey protein prepared from milk contained more total hexose than casein prepared from colostrum, whereas N-acetylneuraminic acid and hexosamine contents were nearly equivalent.