From Aggregation-Prone to Stabilized Whey Protein: Deciphering the Role of Disulfide Bonds and Individual Proteins in Thermal Resistance Ability

Whey protein (WP) has been gaining popularity in high-protein beverages due to its nutritional advantages. However, its heat-induced aggregation behavior, particularly in salt-containing systems, remains a key barrier to commercialization. Previously, modified whey protein (MWP) with thermostability in the presence of NaCl was synthesized through controlled aggregation. Herein, we disclose the underlying mechanism of how specific protein fractions alter the aggregation behavior of MWP following heating. When heated in NaCl-containing WP system, β-lg, α-la, and BSA all contributed to forming large aggregates via covalent interactions. This was supported by a dramatic decrement in the relative concentration of β-lg and α-la in WP, decreasing from 55% and 30% (before heating) to 2% and 5% (after heating). However, such thermally induced aggregation behavior was limited in MWP, with β-lg and α-la existing predominantly as soluble aggregates. The restricted aggregation behavior was ascribed to the higher absolute zeta potential and disulfide bonds of MWP compared to WP. These features enabled MWP to resist heat-induced structural unfolding, resulting in the formation of smaller aggregates. The disclosure of whey protein aggregation behavior provides theoretical guidance for formulating high-whey protein beverages with tolerance to ionic and temperature changes.