Caseins and their interactions that modify heat aggregation of whey proteins in commercial dairy mixtures

Chaperon-like action of caseins during milk protein denaturation has not been comprehensively investigated in commercial dairy mixtures. Gel electrophoresis and FTIR spectroscopy were therefore used to assess the interactions and mechanisms of casein mediation in whey protein (WP) heat-denaturation. Milk protein concentrate and WP isolate were used to prepare 10% dispersions with high (30:70), low (5:95) and control (0:100) casein to WP ratios. After pH adjustment to 6.7 or 7.5, samples were heat-treated at 100 °C for 1 min. Gel electrophoresis revealed that higher casein content increased fractions of non-covalently associated protein complexes. Secondary conformations of WPs were least affected by the heating process at pH 7.5 with the high casein inclusion as indicated by FTIR spectroscopy. Hydrophobic associations predominated in controlling the WP heat-aggregation. Caseins appeared to form heat-induced hydrophobic associations to terminate the denaturation and aggregation process of WPs at a certain stage.