This study examines the impact of low-frequency ultrasound on the physicochemical attributes of milk proteins, focusing on various casein-to-whey protein ratios and their interactions with lactose and calcium. Milk systems with varying casein-to-whey protein ratios (0:100, 50:50, 60:40, 80:20), lactose, and various calcium chloride (CaCl2) concentrations (0-30 mM), were exposed to 20 kHz ultrasound for different durations (0, 1, 5, 10 min). A range of physicochemical factors, including particle size, zeta potential, calcium ion activity, pH, and waterholding capacity, were examined. The results revealed that calcium concentration and pH significantly (P < 0.05) influenced the physicochemical and structural properties of milk protein-lactose-calcium systems. FTIR analyses indicated that ultrasound promoted secondary structural changes in milk proteins and enabled the creation of lactose-protein and calcium-lactose complexes. The intermolecular and intramolecular interactions through hydrophobic and covalent bonding prevailed. Understanding these three-way interactions is crucial for innovating stable and shelf-stable dairy formulations, which is essential for advancing dairy processing.
