The Impact of Beta-Casein Genetic Variant on the Physicochemical Properties of Various Fermented Milk Types

Abstract A2 milk, produced by cows which are homozygous for the A2 β-casein genotype (A2A2 β-CN), has recently attracted increasing attention for its potential health benefits, especially for individuals with certain conditions. However, from an industrial perspective, it is essential to consider the technological challenges and implications associated with the processing of A2 milk. The aim of the current study was to evaluate the effect of the β-CN genetic variant in milk of Simmental cows on the physicochemical, sensory and microbiological quality of selected types of fermented milks. Probiotic yoghurt (ABT-yoghurt), kefir and cultured milk were produced from A2 β-CN milk and compared with those produced from A1 β-CN milk in terms of chemical composition, acidity, antioxidant capacity (ferric reducing antioxidant power and scavenging activity against DPPH radicals), sensory and microbiological quality, instrumental texture and colour profiles, as well as rheological characteristics. The study found no significant differences in basic chemical composition, acidity, antioxidant properties and microbial quality between A1 and A2 fermented milks. Textural and rheological differences related to the β-CN variant were more pronounced in probiotic yoghurts made from A2 milk, which exhibited higher hardness and viscosity, as well as lower structural resistance to deformation. Colour stability remained high across all variants and storage times, with no visually perceptible differences. The sensory quality of cultured milk was rated higher in the A2 variant compared to the A1 variant, due to its better consistency and appearance. In conclusion, A2 milk is well-suited for the production of various types of fermented milk, maintaining microbiological and sensory quality, providing good consistency and texture, though it may need gentler post-production handling.