摘要 : Milk samples from a single source were subjected to a range of heat treatment (80-110deg C for 0-110 s) and processed into 24 dried whole milk samples. The level of whey protein denaturation was estimated using the whey protein ni... 展开 Milk samples from a single source were subjected to a range of heat treatment (80-110deg C for 0-110 s) and processed into 24 dried whole milk samples. The level of whey protein denaturation was estimated using the whey protein nitrogen index (WPNI), areactive sulphydryl groups (RSH) assay and native polyacrylamide gel electrophoresis (native-PAGE). The individual (alpha-lactalbumin (alpha-La), beta-lactoglobulin A (beta-Lg A) and beta-lactoglobulin B (beta-Lg B)) and combined (total native beta-lactoglobulin (beta-Lg total), total native whey protein) whey proteins were measured. Inter-correlations between the 3 methods were examined. Relatively slight correlations were observed between the WPNI or RSH and native alpha-La. High positive correlations were observed between the WPNI and native beta-Lg A, beta-Lg B, beta-Lg total and total native whey protein, whereas high negative correlations were observed between the RSH and native beta-Lg A, beta-Lg B and beta-Lg total. Although high negative correlations were observed between the WPNI or total native whey protein and the RSH, the curves plateaued at low WPNI or native whey protein concentrations, indicating that a maximum level of RSH was obtained. It is suggested that the WPNI and native-PAGE techniques measure similar properties of milk (i.e. native whey proteins). In contrast, the RSH assay is a measure of the degree of denaturation of whey proteins and is therefore a complementary analytical technique. 收起