Solubility and aggregation of commercial α-lactalbumin at neutral pH

The aggregation behavior of two commercial samples of α-lactalbumin (α-La) heated at 95 °C at neutral pH in a complex mineral salt environment was investigated. The objective was to understand the effects of variability between α-La samples and relative concentration of β-lactoglobulin (β-Lg) on aggregate size development, as measured by light scattering and turbidity development. The effect of protein net charge was evaluated with a solubility method and the role of thiol groups was evaluated by reaction with DTNB. The sample with the highest level of β-Lg had higher solubility at pH 6.75 and 6.8, yielded more reactive thiol groups, had a 25% faster first-order rate constant, and formed spherical aggregates with a much higher molecular weight than those produced in the sample containing less β-Lg. Adding increasing quantities of β-Lg to the samples generally decreased reversibility and altered the aggregation process; however, other factors appear to be involved in determining aggregate properties.