Effect of heat treatment on physicochemical and emulsifying properties of polymerized whey protein concentrate and polymerized whey protein isolate

Abstract

Whey proteins (WP) have many nutritional and beneficial therapeutic properties. Whey proteins isolate (WPI) and whey protein concentrate (WPC) are the two major forms of WP, which are indispensable for the functional and nutritional properties of foods. The core aim of this research work was to study the effect of heat treatment on physicochemical and emulsifying properties of polymerized whey protein concentrate and polymerized whey protein isolate. Whey protein solutions (8, 10, 12 w/v %) were heated at temperatures (80, 85, 90 °C) for 30 min, and the physicochemical, emulsification and stability indices properties of WPC and WPI thermal polymers were scrutinized. Results revealed that the content of free sulfhydryl groups, zeta potential and the EAI of polymerized whey protein (PWP) were lower than those of native whey protein (WP) under the same conditions. Meanwhile, the viscosity of PWP was increased with increase in temperature and protein concentration. Additionally, both EAI and ESI of polymerized whey protein isolate (PWPI) were higher than those of polymerized whey protein concentrate (PWPC). TEM and SDS-PAGE results clearly demonstrated that heating induced the formation of large protein aggregates. Conclusively, PWPI network was more homogeneous, stable and denser than that of PWPC.