Acid-induced gelation properties of a novel milk protein concentrate containing preaggregated whey proteins

Milk protein concentrate (MPC) is widely used in high-protein foods. However, increasing protein content often leads to undesirable functional and sensory attributes in the finished products. Interactions between whey proteins and caseins during heat treatment play a critical role in determining the structure and functionality of high-protein systems. In this study, a modified MPC containing caseins and preaggregated whey proteins was evaluated for its impact on acid-induced gelation. A model MPC was prepared by blending micellar casein concentrate (MCC) and milk whey protein isolate (mWPI) to achieve an 80:20 casein-to-whey ratio and was considered as the control MPC. Preaggregated whey proteins were produced by heating mWPI at pH 3.0 or pH 7.0 under constant shear, followed by adjusting the pH back to 6.8 and subsequently blending it with MCC. Heating mWPI at pH 7.0 resulted in significantly larger pre-aggregates (87.48 ± 3.22 nm) than heating at pH 3.0 (74.36 ± 1.33 nm; P < 0.05). After readjustment to pH 6.8, samples heated at pH 3.0 exhibited significantly higher viscosity (13.28 ± 0.98 mPa·s) and larger mean particle size (1580.34 ± 25.30 nm) compared with those heated at pH 7.0 (7.52 ± 0.53 mPa·s; 99.4 ± 9.86 nm). During acid-induced gelation, modified MPC containing whey proteins preaggregated at pH 3.0 showed a longer gelation time (25 min) and lower maximum storage modulus (1394.35 ± 62.15 Pa) compared with samples containing pre-aggregates formed at pH 7.0 (9 min; 2117.08 ± 15.59 Pa). These results demonstrate that pre-aggregation conditions of whey proteins strongly influence casein-whey interactions, viscosity, and gelation behavior. The new ingredients can potentially help in the development of a wide range of high-protein products, such as low viscosity drinkable yogurt, yogurt with reduced graininess. Overall, modified MPC containing preaggregated whey proteins shows potential as a functional ingredient for tailoring the rheological and structural properties of high-protein dairy systems.