Innovative rice alcohol soluble protein-casein matrix for encapsulating purple rice bran anthocyanins: Enhanced digestive stability and bioaccessibility in Caco-2 cell monolayer model.

Purple rice (Oryza Sativa L.) bran anthocyanin (PRA) is a group of bioactive compounds with recognized health benefits, yet its application is limited by poor stability. This study developed a novel delivery system using rice alcohol soluble protein (RASP) and casein (CAS) to encapsulate PRA via an antisolvent precipitation method at neutral pH. Successful encapsulation and strong protein-anthocyanin interactions were confirmed by UV-Vis and FTIR spectroscopy, along with fluorescence quenching analysis. The optimal RASP:CAS ratio (3:1, w/w) produced microcapsule with a hydrodynamic diameter of 259 ± 4.87 nm and zeta potential of -31.00 mV. The thermodynamic parameters at 298, 303 and 308 K showed that RASP-CAS composite matrix (3:1) with PRA solution (0.05 %-0.25 %) had -18.10 to -18.70 KJ/mol of △G values, -30.01 KJ/mol of △H value and -38.20 J/(mol·K) of △S value, indicating a static quenching mechanism during the formation of a non-fluorescent RASP-CAS-PRA microcapsule. SEM images revealed spherical particles with smooth surfaces and average particle diameters ranging from 309.1 to 684.7 nm, depending on the encapsulation conditions. The 6:1 wall-to-core ratio achieved 86 % encapsulation efficiency. Encapsulated PRA demonstrated improved stability under varying pH (3.5-6.5), temperatures (40-80 °C), storage durations (up to 10 days), and in vitro digestion conditions. Furthermore, transport studies using a Caco-2 cell monolayer demonstrated markedly improved absorption of microencapsulated anthocyanins, with pelargonidin-3-glucoside and cyanidin-3-glucoside increasing by 73.02 % and 64.67 %, respectively. These findings underscore the effectiveness of the RASP-CAS matrix in stabilizing PRA and enhancing its bioavailability, highlighting its potential as an advanced delivery system for nutraceutical and precision nutrition applications.