Dissociation and interfacial properties of A1 and A2 variants of β-CN

Abstract

Background

The interfacial properties of β-casein (β-CN) are associated with several physicochemical characteristics, including self-association, dissociation and chaperone-like activities. These characteristics can be beneficial to the dairy industry, such as for emulsification and foam stabilisation. Genetic variants of β-casein (e.g. A1 and A2) may influence these properties, but little is known about the significance of this.

Aims and Methods

This study investigated the effects of A1 and A2 β-CN genetic variants on these characteristics using purified casein recovered from the milk of cows with the respective genotype. Caseins were recovered by sequential microfiltration and physicochemical properties relating to interfacial properties were studied, as well as the dissociation properties of the caseins from micelles on ultracentrifugation in the cold.

Major Findings

During heating and cooling, solutions of A1 β-CN remained more stable than those of A2 β-CN, showing minimal changes in particle size and turbidity. Significantly better foaming properties were associated with A2 β-CN than A1 β-CN. Caseins in milk containing A2 β-CN tended to dissociate more intensively after ultracentrifugation at 4°C in comparison with milk containing A1 β-CN.

Scientific and Industrial Implications

These findings suggest that A1 β-CN contributes to higher stability in certain applications, while A2 β-CN enhances foaming capacity. This may have implications for production of dairy ingredients from milk obtained from cows of genotyped herds.