Effect of Heat Treatment on Denaturation of Bovine α-Lactalbumin:  Determination of Kinetic and Thermodynamic Parameters

The effect of heat treatment on the denaturation of α-lactalbumin was studied, under different conditions, over a temperature range of 78−94 °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 α-lactalbumin, measured by the loss of immunoreactivity, could be described as an order of reaction of n = 1.5. Results obtained indicated that α-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-α-lactalbumin decreased with the binding of oleic acid.

Keywords: Heat denaturation; bovine milk; native lactalbumin; apo-α-lactalbumin; kinetics; thermodynamics