Properties and Proanthocyanidin-Loading Capacity of Acid-Induced Micellar Casein-Sodium Alginate Emulsion Gels

In this work, oil-in-water (O/W) emulsion gels with 70% oil phase were prepared using micellar casein (MC) and sodium alginate (SA) as substrates with the addition of gluconate-δ-lactone (GDL) as acidifying agent. The effects of GDL addition on the microstructure, stability and rheological properties of emulsion gels were studied, and the release characteristics of emulsion gels loaded with proanthocyanidins (PC) were analyzed. The results showed that with increasing GDL concentration, the average size of oil droplets in emulsion gels decreased, and it gradually decreased during the storage period. GDL acidification improved the apparent viscosity and storage modulus of emulsion gels, and this effect increased with GDL concentration. The microstructure of emulsion gels did not change significantly after heat treatment at 65 or 80 ℃ for 30 min. Meanwhile, the emulsion gels were stable to acidic and basic conditions as well as storage. In addition, the release rate of PC-loaded emulsion gels was higher than that of free PC during simulated intestinal digestion, and the cumulative release rate at 10 h increased with GDL concentration. The results of this study could provide a reference for the preparation of emulsion gels based on MC and the improvement of PC stability.