The effect of thermal ultrasonic treatment on the interaction between tea polyphenols and goat milk proteins at different ratios

Tea polyphenol binding improves milk protein complex functionality. • Optimal TP-to-protein ratios are 0.4 for whey and 2 for casein. • Thermal-ultrasound treatment strengthens protein-polyphenol binding. • Complexes show enhanced antioxidant, foaming, and emulsifying properties. This study investigated the effects of thermal–ultrasound treatment on the interactions between goat milk proteins, including whey protein and casein, and tea polyphenols. The structural and functional properties of the resulting complexes were systematically evaluated at different tea polyphenol-to-protein ratios. Tea polyphenols improved protein functionality in a concentration-dependent manner, with the optimal ratios identified as 0.4 for whey protein and 2 for casein. At these ratios, thermal–ultrasound treatment increased the solubility of whey protein and casein to 95.16% and 92.78%, respectively, compared with untreated samples, and enhanced their tea polyphenol loading capacities by 10.68% and 12.53%. Moreover, foaming capacity was markedly improved, reaching 124.33% for whey protein and 130.00% for casein. Molecular docking further revealed hydrogen bonding and hydrophobic interactions between EGCG and β-lactoglobulin or β-casein. In summary, thermal–ultrasound treatment significantly enhances protein-tea polyphenol interactions, thereby improving the functional properties of the goat milk system Download: Download high-res image (337KB) Download: Download full-size image