The effect of milk protein contents on the rennet coagulation properties of milk from individual dairy cows

The objective of this study was to investigate the effect of milk proteins on rennet coagulation properties. Milk samples (n = 516) were taken from 54 cows once a month during one full lactation period and analysed for rennet coagulation properties, and for contents of αS1-, αS2-, β- and κ-casein, and β-lactoglobulin. The contents of the analysed milk proteins and the relative contents of different caseins (Cn) in total casein were significantly influenced by sampling month, breed, and the month of lactation. An increase in milk protein, casein, casein fractions, and the casein number decreased the rennet coagulation time of milk and increased curd firmness. Milk formed a firmer curd when the relative content of αS1- and β-Cn in total casein was lower, or the relative content of κ-Cn in total casein was higher. Higher values of κ-Cn:β-Cn and κ-Cn:αS-Cn ratios had a positive effect on curd firmness.