Mechanism for Formation of Heat-induced Milk Whey Protein Gel with Pre-treatment using Aqueous Ethanol: The Ultrasonic Properties and Protein Secondary Structure

Abstract

The effects of pre-treatment with aqueous ethanol on heat-induced gel formation of commercial milk whey protein were investigated using surface hydrophobicity analysis, rheological measurement, ultrasound spectroscopy and secondary structure analysis by FT-IR. Among the three kinds of whey proteins pre-treated with 10, 25 and 50% aqueous ethanol, the 10% treated sample showed a high gel forming ability based on the higher compressibility of the sample system, as well as the higher frequency dependency of the ultrasonic attenuation, which showed involvement of more proteins in construction of the network during heat treatment. It is suggested that these remarkable gel properties are due to stabilization of the native-like structure in the secondary structure level even at 60 °C, and formation of the aggregated particles similar to that of milk whey without aqueous ethanol pre-treatment in scanning electron microscopy analysis. These findings suggested that pre-treatment using aqueous ethanol for protein is a good technique for improving food functional properties.