Impact of Thermal Processing and Protein Fortification on the Denaturation and Sensory Attributes of High-Protein Dairy Systems

The increasing demand for high-protein nutritional supplements has led to the widespread incorporation of milk protein concentrate (MPC) and whey protein isolate (WPI) into dairy systems; however, their synergistic effects on thermal stability and sensory quality remain poorly understood. This study systematically investigated the heat-induced denaturation and volatile organic compound (VOC) evolution in fortified whole milk (WM) systems (80 °C, 30 min) using a multidimensional flavoromics approach. We integrated SDS-PAGE and HPLC to quantify protein denaturation, alongside HS-SPME-arrow-GC-MS and descriptive sensory analysis (QDA) to map the resulting volatilome and aroma profile. HPLC analysis showed that WPI-fortified systems maintained higher initial β-lactoglobulin levels and exhibited a numerical 19.7% reduction in recoverable soluble β-LG after heat treatment. In contrast, MPC-containing systems showed less pronounced high-molecular-weight aggregation in non-reducing SDS-PAGE, suggesting that the casein-rich matrix may modulate whey protein aggregation. VOC profiling indicated a prominent contribution of lipid oxidation products, including hexanal and nonanal, together with formulation-dependent differences in sulfur-containing and ketonic compounds. Correlation analysis suggested associations between the volatile profiles and selected sensory attributes. Although sulfur-containing compounds were detected, the sensory results indicated formulation-dependent differences in cooked aroma, suggesting that the casein-rich matrix may influence volatile retention and release. Collectively, these findings indicate that protein-specific matrix interactions contribute to the thermal and sensory behavior of protein-fortified dairy systems and provide initial guidance for the formulation of thermally stable, protein-enriched dairy beverages.