Structure–Function Effect of Heat Treatment on the Interfacial and Foaming Properties of Mixed Whey Protein Isolate/Persian Gum (Amygdalus scoparia Spach) Solutions

This study aimed to elucidate the impact of Persian Gum (PG; Amygdalus scoparia Spach) on the heat-induced aggregation and interfacial behavior of whey protein isolate (WPI). To achieve this, pure WPI and mixed WPI-PG systems were subjected to thermal treatments between 25 and 85 °C, and their structural and functional changes were characterized using fluorescence spectroscopy, UV-vis absorption, turbidity and bulk viscosity measurements, interfacial shear and dilatational rheology, and foaming assessments. The presence of PG altered the aggregation pathway of WPI in a temperature-dependent manner, producing smaller, more soluble complexes with lower turbidity, particularly at higher temperatures. Both pure WPI and WPI-PG mixtures exhibited increased surface hydrophobicity upon heating; however, PG generally reduced the dilatational elastic modulus except at 85 °C, where the mixed system showed a higher modulus than WPI alone. In contrast, the interfacial shear modulus increased over time in all samples, with consistently higher values observed for WPI-PG mixtures at both 25 °C and 85 °C. Notably, three complementary methods were employed to evaluate foaming properties and interfacial behavior in this study, revealing that factors such as concentration, measurement time, and methodological approach strongly influence the observed responses, highlighting the complexity of interpreting protein-polysaccharide interactions. The ability of PG to modulate WPI unfolding and limit the formation of large aggregates during heating demonstrates a previously unreported mechanism by which PG tailors heat-induced protein network formation. These findings underscore the potential of Persian Gum as a functional polysaccharide for designing heat-treated food systems with controlled aggregation behavior and optimized interfacial performance.