Increasing the thermal stability of high-protein beverages through the modification of whey proteins through thermal...

Colloidal stability during thermal processing and subsequent storage is one of the most important factors in selecting ingredients for high-protein beverages. The interaction between whey proteins and caseins in high-protein systems influences their stability during high-heat treatments such as UHT sterilization. The heat-labile nature of whey proteins leads to denaturation and aggregation, thereby reducing their applicability. This work aims to study the effects of modified whey proteins, produced through thermal processing, on the heat stability of high-protein beverages. The study was conducted in 2 phases. In the first phase, acidified whey protein isolate (AWPI, pH 3.5) was used to form modified whey proteins. The modified whey protein was prepared by heating reconstituted AWPI at 90°C for 10 min in a high-shear mixer operating at 10,000 rpm. Surface charge, particle size, surface hydrophobicity, and total and free sulfhydryl groups were measured. Adjusting the pH of untreated AWPI to 6.8 served as the control. Increased surface hydrophobicity and availability of sulfhydryl groups were observed after heating and shearing, but the resulting aggregates were smaller (~61 nm) due to strong electrostatic repulsion. In the second phase, the modified whey protein was incorporated into high-protein systems containing 8% and 10% total protein, with casein-to-whey protein ratios of 80:20, 60:40, and 50:50. Viscosity, particle size, and heat coagulation time were measured. As the whey protein proportion increased, the heat coagulation time decreased. However, the use of modified whey proteins improved heat stability even at 10% protein and a 50:50 casein-to-whey ratio, extending the coagulation time from 0.8 to 2 min. The formation of small whey protein aggregates during modification contributed to the increased heat stability. Therefore, small aggregate formation of whey proteins at a lower pH can reduce interactions between casein and whey proteins and enhance heat stability in high-protein systems.