Kinetic study on the combined effect of high pressure and temperature on the physico-chemical properties of egg white proteins

A kinetic study was conducted on the effect of pressure (525-600 MPa) at different temperature levels (10, 25, and 40 degrees C) on selected physico-chemical properties of egg white solutions (turbidity, solubility, residual denaturation enthalpy, surface hydrophobicity, and sulfhydryl content). The pressure induced decrease in residual denaturation enthalpy, solubility and buried SH content, and increase in turbidity and surface hydrophobicity could be described by a fractional conversion model, while the loss of SH groups due to SH oxidation could be described by a second order kinetic model. At 25 degrees C, pressure-induced denaturation was favoured by increased pressure, as evidenced by the negative activation volumes for the Eyring equation. Thus, higher rate constants were obtained for higher pressures. Furthermore, pressure-induced denaturation was enhanced by pressure treatment at lower temperatures. For all properties, except total SH content, a negative apparent activation energy for the Arrhenius equation was obtained, resulting in lower rate constants at higher temperatures. This is opposite to what is observed for heat treatment at ambient pressure, indicating an antagonistic effect of temperature and pressure in the temperature-pressure range studied. At higher temperature (60 degrees C), pressure-induced egg white protein denaturation more closely resembles heat-induced denaturation. (c) 2005 Elsevier Ltd. All rights reserved.