Effect of the protein content and amount of native whey protein on properties of heat and acid-induced milk gels

The amount of native whey protein (NWP) denaturation in dairy ingredients, as indicated by whey protein nitrogen index (WPNI), is expected to play a crucial role in defining the composition and texture of heat and acid-induced milk gels. In this study, milk formulations with total protein content varying from 3.4% to 6.0% (w/w) and variable amount of NWP were formulated using whey protein isolate, skim milk powders with varying NWP, or microparticulate whey protein. Gels were prepared by pre-heating to 90 °C and direct acidification to pH 5.2. Increasing the total protein concentration from 3.4% to 6.0% increased gel yield and protein content and produced denser gel networks, reflected by lower moisture contents and higher gel firmness and Young’s modulus. Variations in NWP content influenced gel composition and textural properties; however, no consistent trend between NWP level and gel yield or calcium content was observed across all formulations. Overall, these results demonstrate how protein denaturation in milk formulations modulate the composition and texture of heat and acid-induced dairy gels.