The effects of high-intensity ultrasound on the structural and functional properties of α-Lactalbumin, β-Lactoglobulin and their mixtures

In this study, the structural and functional changes of pure and 3:1 mixtures of beta-Lactoglobulin (beta-LG) and alpha-Lactalbumin (alpha-LA), the most abundant whey proteins in milk were studied after sonication at 20 kHz (31 W) for up to 60 min. The reactive thiol content and surface hydrophobicity of pure beta-LG increased continuously during sonication, suggesting an unfolding of the dimer structure. Minor secondary and tertiary structural changes were also observed by circular dichroism. The alpha-LA protein appeared to be more strongly affected by sonication, with significant increases in surface hydrophobicity. The results suggest that sonication has a greater effect on alpha-LA than on beta-LG, which means that the properties of their mixture differ substantially from that of either protein in isolation. (C) 2012 Elsevier Ltd. All rights reserved.