Thermal denaturation of beta-lactoglobulin A, B and C in heated skim milk

摘要

Whey-protein-free skim milk samples were prepared by a combination of ultrafiltration and microfiltration techniques. The desired concentrations of alpha -lactalbumin and the A, B or C variant of beta -lactoglobulin (beta -LG) were added back to the milk. The milk samples were heated at temperatures from 75 to 100 degreesC and the rates of beta -LG denaturation were determined using quantitative polyacrylamide gel electrophoresis. At all temperatures, the rate of denaturation of beta -LG was most rapid for the B variant, with the A variant intermediate and the C variant most thermostable. The differences in thermostabilities were quite large at temperatures below about 85 degreesC, but much smaller at higher temperatures. The differences in thermostabilities between the different variants of beta -LG are probably related to the differences in structure, charge and self-association behaviour that are induced by the small changes in primary sequence between the variants.