Dual-Cross-Linked Gelatin-Polysaccharide Hydrogel Beads for Efficient Protection and Controlled Release of Probiotics

This study fabricated gelatin–sodium alginate-carboxylated cellulose nanofibers (GSC) composite hydrogel beads using a dual-cross-linking strategy based on Ca2+ and transglutaminase (TG) for probiotic encapsulation. The influences of TG cross-linking time on the properties of hydrogel beads and probiotic incorporation were investigated. The results indicated that probiotics were effectively immobilized through hydrophobic interactions with gelatin and electrostatic interactions with Ca2+. The internal structure of the hydrogel beads became denser as the TG cross-linking time increased. The survival rates reached 87.9%, 70.9%, and 34.4% after low-temperature storage, freeze-drying, and heat treatment at 65 °C for 10 min, respectively. Furthermore, a high viable count was maintained after 2 weeks of storage in beverage matrices including orange juice and yogurt. Following in vitro simulated gastrointestinal digestion, the hydrogel beads released the probiotics via a swelling mechanism, increasing the survival rate up to 85%, while the release duration was extended to 4–6 h. GSC hydrogel beads significantly improved the stability and delivery of probiotics, among which GSC-TG30-LP showed the best overall performance. These findings demonstrate that the GSC hydrogel beads can be applied as an effective encapsulation carrier for probiotics, showing potential applications in the food industry.