Effect of ultrasound pretreatment on the physicochemical properties and simulated gastrointestinal digestibility of micellar casein concentrates

Abstract

In this study, microfiltered casein micelle retentates were treated with sonication within 15 min prior to spray drying, and the impact of ultrasound pretreatment on the physicochemical, functional, and digestion properties of the resultant micellar casein concentrates were investigated. The results showed that the intrinsic fluorescence intensities of casein samples increased after extending the ultrasound pretreatment time from 2 to 6 min, but decreased if pretreatment time was further prolonged; this was also true for the oil absorption capacity. Additionally, there was a reduction in particle size and thermal stability and an increase in the solubility of pretreated samples in the pH range of 4–8 compared with controls. Bulk and tapped density values decreased after extending the sonication time from 2 to 4 min, but increased if sonication time was further prolonged. No significant changes in the secondary structure of the samples were observed after sonication. An obvious disintegration of micellar casein particles was observed by scanning electron microscopy following ultrasound pretreatment times up to 10 min, resulting in improved digestibility in simulated intestinal fluid. Thus, we concluded that prolonged ultrasound pretreatment facilitates enhanced digestion of micellar casein concentrate and its products.