Analysis of the acid-soluble contents of alpha-lactalbumin, beta-lactoglobulin, serum albumin and of the immunoglobulin fraction in pasteurized milk.

For characterizing low heat load in the pasteurizing area, the denaturation behaviour of alpha -lactalbumin, beta -lactoglobulin A and B, bovine serum albumin and immunoglobulin was investigated in the temperature range 60 de greesC to 90 degreesC. Raw milk (3.5% fat, 3.6% protein, 12.79% dry matter) was indirectly heated in a pilot heat plant with holding times between 20. 2 to 163 s. Subsequently, the acid soluble content of the individual whey p roteins was analyzed by liquid chromatography. Except for immunoglobulin, a significant denaturation of the whey proteins could only be detected at te mperatures above 70 degreesC. For the temperature/time-combination, an incr easing denaturation was found in the following order: alpha -lactalbumin < <beta>-lactoglobulin A < <beta>-lactoglobulin B < serum albumin < immunoglo bulin. Due to the wide variation range of the individual whey proteins in r aw milk, particularly of the whey proteins serum albumin and immunoglobulin , which are well-suited for the characterization of low heat loads, an eval uation of the heat load is only possible if the initial contents of these p roteins in raw milk are known. The reaction kinetic parameters in the tempe rature range between 75 degreesC and 90 degreesC were evaluated on the basi s of a 1.5 order reaction for beta -lactoglobulin A and B, and a 1st order reaction for cr-lactalbumin, serum albumin and immunoglobulin.