Change in the structural and functional properties of goat milk protein due to pH and heat

Abstract

This study was carried out to investigate the effects of pH and heat on the structure and function of milk proteins by comparing goat milk treated under different pH and temperature conditions. The results showed that pH had a significant effect on the thermal stability of goat milk proteins, and the proteins were least thermally stable at pH 7.7. Except for the pH 6.9 goat milk, the surface hydrophobicities of the milk proteins at various pH values reached their maxima at 85°C. The particle size, zeta potential, and content of regular secondary structure also decreased significantly at 85°C, and the turbidity of milk proteins under alkaline pH conditions was lower than that under acidic conditions. It was concluded that alkaline conditions resulted in better emulsion stability and oil-holding capacity, and acidic conditions offered better foaming ability, foam stability, and water-holding capacity for goat milk protein during heat processing. It can also be seen that 85°C was the key temperature for milk proteins after changing the pH of the milk. This paper provides a theoretical basis for optimizing the processing conditions for goat milk and the applications of goat milk proteins.

Keywords: functional property; goat milk protein; pH-heat induction; structural property.