Size reduction of "reformed casein micelles" by high-power ultrasound and high hydrostatic pressure.

Abstract

We investigated the effect of ultrasound (US) and high hydrostatic pressure (HHP) on the size of reformed casein micelles (RMCs) obtained by titrating calcium and phosphorous solution into sodium caseinate solutions. Both US and HHP reduced the size of the RMCs. A decrease in size from ~200nm to ~170nm when US (20kHz, 0.46W/mL) was applied for 30min; and down to ~85nm when HHP was applied 500MPa for 15min. Electron microscopic analysis showed that the RMCs before and after US are similar to milk native casein micelles, and that HHP extensively disintegrated the RMCs. Small angle X-ray scattering and SDS-PAGE showed that the internal structure of the RMCs as well as the casein molecules are not affected by the US and HHP treatments.