Effect of heat-treatment on the physico-chemical properties of egg white proteins: A kinetic study

In this study, kinetic models were established to describe the heat-induced changes in selected physico-chemical properties of egg white proteins. These changes were studied in a temperature range of 50-85 degrees C and two pH levels were selected, to mimic the pH of fresh (pH 7.6) and aged egg white (pH 8.8). The heat-induced decrease of residual denaturation enthalpy and amount of buried sulfbydryl groups and the increase in surface hydrophobicity could be described at both pH levels with a first order fractional conversion model, while this model could only be applied at pH 7.6 to describe the loss of protein solubility and increase in turbidity due to heat-treatment. A second order model could be used to characterize the heat-induced decrease of total sulfhydryl content. The rate constants to describe the changes in denaturation enthalpy and buried sulfhydryl content were more sensitive to temperature increase than the other properties studied, as indicated by a higher activation energy. These kinetic data can be used to predict heat-induced changes in related functional properties of egg white proteins. (c) 2005 Elsevier Ltd. All rights reserved.