Effect of heat treatment on denaturation of bovine alpha-lactalbumin: determination of kinetic and thermodynamic parameters

The effect of heat treatment on the denaturation of alpha-lactalbumin was studied, under different conditions, over a temperature range of 78-94 degrees C. The concentration of the residual immunoreactive protein after different treatments was determined by kinetic analysis, obtaining D and Z values. Thermodynamic parameters were also calculated. Denaturation of alpha-lactalbumin, measured by the loss of immunoreactivity, could be described as an order of reaction of n = 1.5. Results obtained indicated that alpha-lactalbumin was more heat-sensitive when treated in milk than in phosphate buffer. The protein was also denatured more rapidly in the apo form than in the calcium-saturated form. Besides, the thermal stability of apo-alpha-lactalbumin decreased with the binding of oleic acid.