| Abstract
| - Milk samples (5 mL) from cows, homozygous for κ-casein A and eitherhomozygous A (n = 14) or B(n = 12) or heterozygous AB (n = 14) forβ-lactoglobulin (β-lg), were heated at 90 °C for 0−10min,followed by ultracentrifugation at 100000g. The nativewhey proteins in the supernatant werethereafter analyzed by fast performance liquid chromatography (FPLC),and the decrease of wheyproteins was recorded. The reaction orders for the heat-inducedloss of β-lg were found to be 0.53,0.65, and 0.91 for β-lg A, β-lg A+B, and β-lg B, respectively,in milk containing the A variant ofκ-casein. The rate of heat-induced loss, expressed as thehalf-life (t1/2) of the reaction, was foundtobe 340 and 270 s for β-lg A and B, respectively, in milk fromhomozygous cows. In milk fromheterozygous cows (β-lg A+B), this value was 330 s. Aftercorrection for the casein number, thet1/2value for β-lg B was still notably lower than for β-lg A. Theresults, therefore, showed that theconcentration of β-lg B decreased more rapidly than β-lg A in skimmilk containing κ-casein A,probably due to differences in hydrophobicity between the geneticvariants of β-lg. Keywords: β-Lactoglobulin; κ-casein; casein micelles;heat treatment; genetic polymorphism
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