The Kinetics of Heat-Induced Structural Changes of β-Lactoglobulin

Heat-induced structural changes of β-lactoglobulin were studied at temperatures ranging from 67.5 to 82.5°C, and at pH 7.5. These changes were monitored by measurement of surface hydrophobicity, thiol availability, and protein solubility. Kinetic studies were conducted to quantitatively describe the contribution of hydrophobic and SH/SS interchange reactions to the thermal structural changes of β-lactoglobulin. Results indicate that β-lactoglobulin is sensitive to heat-induced interchange reactions with consequences for protein solubility. The extent of changes measured by the increase in surface hydrophobicity and the decrease in slow-reacting SH groups content could be described by a first-order fractional conversion model and were characterized by activation energy values of 233.9 ± 8.6 and 148.2 ± 6.7 kJ/mol, respectively. The break in the Arrhenius plot suggested in literature for β-lactoglobulin denaturation was confirmed in this study only for the kinetics of exposed SH groups.