The Functional Properties and In Vitro Digestibility of Casein-Rich Powder Prepared by Calcium Chelation and Spray Drying

To improve the functional performance and digestibility of casein-rich ingredients, this study investigated the effects of trisodium citrate (TC) chelation and spray drying on the functional properties and in vitro digestibility of micellar casein isolate (MCI). TC chelation improved the foaming, emulsifying, gelling, and digestive properties of casein to different extents. Compared with MCI, trisodium citrate-chelated casein (TCC) exhibited significantly enhanced foaming capacity; specifically, the foaming capacities of TCC-40 and TCC-60 increased to 58.0% and 60.0%, respectively. TC reduced particle size, leading to increased foam volume, whereas foam stability decreased at higher chelation levels. In terms of emulsifying properties, TCC-10 exhibited optimal performance, with most emulsion droplet diameters distributed within 1–5 μm. TC chelation induced a significant negative shift in zeta potential (p < 0.05), suggesting improved emulsion stability. Gelation behavior was linked with concentration, showing TCC-40 induced the shortest gelation time (3.98 min) and the highest storage modulus. TC significantly enhanced casein digestibility in both adult and elderly in vitro digestion models, with digestion efficiency in the elderly model approaching that of the adult model. Confocal laser scanning microscopy (CLSM) pictures indicated that calcium chelation reduced gastric floc compactness, facilitating enzymatic access and improving protein hydrolysis efficiency. The study reveals the advantage of calcium chelation on the functional properties and digestibility of casein-based powder.