Effects of Different Thermal Sterilization Conditions on Structural and Functional Properties of Whey and Casein Proteins in Goat Milk

Abstract

This study investigated the effects of different thermal sterilization conditions on the structural and functional properties of whey and caseins in goat milk. The commonly used industrial sterilization conditions including 65 ℃ for 30 min, 80 ℃ for 30 s, 95 ℃ for 5 min and 135 ℃ for 4 s were selected to treat goat milk, and whey and casein proteins were separated from the treated milk. Circular dichroism (CD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, fluorescence spectroscopy, laser confocal scanning microscopy (LCSM) and atomic force microscopy (AFM) were used to analyze the changes in protein structure and properties. The results showed that the structures of whey and casein proteins changed little after treatment at 65 ℃ for 30 min and 80 ℃ for 30 s, and the increase in protein unfolding and surface hydrophobicity resulted in better foaming and emulsifying properties of whey and casein proteins. The treatments at 95 ℃ for 5 min and 135 ℃ for 4 s resulted in a significant decrease in the relative content of α-helix, a significant increase in the relative content of random coil, severe denaturation of the proteins, and a decrease in solubility and surface hydrophobicity, which adversely affected the stability of functional properties of goat milk proteins. The above results provide a reference for optimizing the quality and stability of goat milk products, and help to develop functional goat milk products.

Keywords

• goat milk; whey protein; casein; structural properties; functional features