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.