Susceptibility of κ-Casein to degradation by microbial proteases in experimentally contaminated milk from cows with different β-Casein genotypes

The properties of A2 milk are currently under debate, with limited information available on the action of microbial proteases in milk from cows with different β-casein genotypes. The study aimed to experimentally contaminate milk from cows with A1A1, A1A2, and A2A2 β-casein genotypes with Bacillus cereus s.s. and Pseudomonas fluorescens and to quantify CMP at different incubation times in order to determine whether the three genotypes influence the microbial degradation of κ-CN. There was an increase in the concentration of free CMP over time, regardless of genotype or treatment. The A1A1 genotype showed a lower rate of κ-CN degradation and a lower concentration of free CMP. The degradation by Pseudomonas fluorescens was slower than that by Bacillus cereus s.s. These results demonstrate the influence of genotypes on the microbial degradation of κ-CN, suggesting that A2 milk, despite its enhanced digestibility, may be more susceptible to degradation by microbial proteases.