Separation of β-Lactoglobulin from Other Milk Serum Proteins by Trichloroacetic Acid

Abstract

[beta]-Lactoglobulin can be easily separated from milk because it is the whey protein most resistant to precipitation by trichloroacetic acid. After removing casein from milk by acid precipitation, the residual whey is made up to contain 3% trichloroacetic acid. All proteins other than [beta]-lactoglobulin precipitate and can be filtered. The filtrate is concentrated by negative pressure dialysis, dialyzed free of low molecular weight materials, and lyophilized. The recovered [beta]-lactoglobulin had a specific rotation of -27.8 at 575 m[mu], pH 4.75, an intrinsic viscosity of 4.1, and an electrophoretic mobility of -5.65 x 10-5 em2/v/sec in veronal buffer pH 8.6, 0.1 ionic strength. It is monophoretic in this buffer. These values agree closely with those obtained in similar analyses of a commercially available sample of 3 x crystallized [beta]-lactoglobulin prepared by salt fractionation.