Differential apparent morphology, structures, and in vitro digestion properties of casein micelle+β-lactoglobulin thermal aggregates modulated by κ-casein genotypes.

This study aimed to investigate how κ-casein genotypes influence the apparent morphology, structures and in vitro digestion properties of casein micelle+β-lactoglobulin thermal aggregates (CM+β-Lg). Three CM containing AA (n = 25), AB (n = 22) or BB (n = 24) type κ-casein were isolated from milk of Danish Holstein cows. CM+β-Lg was prepared by high temperature short-time pasteurization (HTST, 75°C 20 s) or ultra-high temperature instantaneous sterilization (UHT, 137°C 5 s), respectively. Results showed that CM+β-Lg containing AA type κ-casein exhibited largest particle size, widest particle size distribution, weakest Zeta-potential, highest relative release of κ-casein, highest extent of β-Lg association, lowest free sulfhydryl groups concentration, highest changing amount of secondary structure of protein, lowest intensity in both exogenous and endogenous fluorescence spectra, loosest structure of the gastric clot, and highest degree of hydrolysis, compared with the other 2 CM+β-Lg. Differences in glycosylation degree of κ-casein and particle size of CM could be reasons.