Milk Powder Formulations with Varying Casein to Whey Ratios and Calcium Addition: Physico-Chemical and Structural Properties and the Effect of Low-Frequency Ultrasound
Yuanyuan Zhao, Tuyen Truong, Jayani Chandrapala
Abstract
This study examined the effect of low-frequency ultrasound (20 kHz, 1 and 5 min) on the physiochemical and structural properties of milk powder formulations with varying casein to whey ratios (0:100, 60:40, and 50:50) and calcium addition (30 mM). The ultrasound treatment led to changes in particle size, with an initial increase in aggregation followed by fragmentation. Calcium addition resulted in looser packing, as evidenced by a decrease in both bulk and tapped densities. DSC analysis indicated that calcium addition stabilized the protein-lactose matrix by increasing the glass transition temperature and reducing the number of thermal events. FTIR analysis revealed structural changes in proteins, with a decrease in β-sheet and β-turn and an increase in α-helix structures. These findings suggest that calcium plays a crucial role in reinforcing the structural integrity of the protein-lactose matrix, while ultrasound-induced mechanical forces lead to dynamic changes in particle size and protein conformation.