Study on preparation, physicochemical properties and in vitro digestion of casein sol/gel induced by citric acid and heat

Casein (CS) gels, valued for their functional properties, are widely utilized in food applications. In this study, CS sol/gels were prepared by citric acid and heat (85 °C) induction at varying pH values and protein concentrations, and their physicochemical properties and <i>in vitro</i> digestion characteristics were further evaluated in order to explore the gel mechanism and the potential application in controlled release of roselle anthocyanins (RA). Stable CS gels formed only at pH 2.0 and protein concentrations ≥12 %, attributed to high solubility and ζ-potential. Moreover, hydrophobic interactions and ionic bonds were the main driving forces. In addition, the CS gel effectively enabled RA controlled release, achieving intestinal release rates of 76.58 % ∼ 83.47 %. but RA reduced the protein digestibility of CS gel by approximately 10 %. These findings provide a theoretical foundation for CS gel developments and applications in functional food.