The effect of β-casein addition on properties and rennet behavior of reassembled casein micelles.

Bovine milk contains four types of caseins with β-casein being one of the most abundant. Previous studies on cow milk have reported seemingly contradictory effects of β-casein on milk renneting behavior. The aim of this study was to gain a better understanding of how β-casein affects the properties and renneting behavior of casein micelles by using a model system of reassembled casein micelles (RCMs). We increased the β-casein ratio of RCMs to 60 % by adjusting the β-casein ratio during or after the reassembly process. We found that reducing the calcium phosphate content to 85 % was necessary for forming stable β-casein enriched RCMs. It was also found that adding β-casein during reassembly resulted in firmer rennet coagulates compared to adding it afterwards. To conclude, the order of adding β-casein significantly affected the structure formation and, consequently, the properties of RCMs.