KINETICS OF BEAN PROTEIN THERMAL DENATURATION

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Abstract
A kinetic model for the thermal denaturation of the 7S protein of common black beans (Phaseolus vulgaris) was developed. Thermal analysis was performed on hydrated (9:1) solutions of the proteins with a differential scanning calorimeter (DSC). Kinetic parameters were obtained by analyzing peaks in the DSC thermogram using the Borchardt and Daniels method. Denaturation temperature for 10% solutions increased from 382 to 387°K when increasing the heating rate from 5 to 30°C/min, while the enthalpy was steady at about 0.4J/g solution. The reaction order for phaseolin denaturation was found to be close to 2.5, with an activation energy of 932 KJ/mol and a pre-exponetial factor of 127 min−1. A critical evaluation of the peak temperature versus heating rate method revealed that the former method was less appropriate and accurate for determining the activation energy of protein denaturation.