Relationship between Β-casein genotypes (A1A1, A1A2, AND A2A2) and coagulation properties of milk and the fatty acid composition and sensory characteristics of dairy products (soft cheese, sour cream, and butter)

Abstract

Milk products are a source of lipids, carbohydrates, proteins, minerals, and vitamins. Although milk is a staple in the diets of many cultures, the demands for specific milk products differ between consumers (some are allergic to cow’s milk proteins or incapable of digesting lactose). However, such consumers are not without options, and multiple studies suggest that milk containing only A2 beta-casein may be an alternative. [1] concluded that people with lactose intolerance reported less abdominal pain while consuming milk containing only A2 beta-casein. Furthermore, a review by [2] concluded that A2 beta-casein milk is a potential remedy for people with a milk protein allergy. We hypothesized that because the CSN2 genotype (A1A1, A1A2, and A2A2) influences milk’s biochemical composition, it should also influence the final product. The study aimed to investigate the viability of breeding crossbred dual-purpose Simmental cows exclusively towards the A2 variant beta-casein by investigating the influence of the CSN2 genotypes, with a focus on the A2A2 genotypes’ influence on the coagulation traits, fatty acid composition, and sensory characteristics of different milk products (soft cheese, sour cream, and butter). We assigned 15 crossbred cows (1⁄2 Swedish red X 1⁄4 Simmental X 1⁄2 Holstein Friesian) into three groups (A1A1, A1A2, and A2A2) of five cows per group. Milk samples for milk products (soft cheese, sour cream, and butter) production were taken following the ISO 707:2008 protocol [3]. Milk coagulation properties were determined by exposing milk samples to rennet enzyme solution. Rennet coagulation time and curd-firming rate were fastest in A2A2 milk and slowest in A1A1 milk. Accordingly, curd firmness was highest in A2A2 milk and lowest in A1A1 milk. A1A1 milk products had higher levels of monounsaturated fatty acids and lower levels of saturated fatty acids. Polyunsaturated fatty acids were mainly found in A2A2 milk products and were lowest in A1A2 products. Although CSN2 genotypes influenced milk coagulation traits and fatty acid content of milk products, they did not influence the latter’s sensory traits.