Enhanced Storage Stability and Gastrointestinal Survival of Lactiplantibacillus plantarum by Sodium Alginate–Resistant Starch–EGCG Composite Encapsulation

The development of functional foods containing probiotics requires strategies to maintain cell viability during processing, storage, and gastrointestinal (GI) transit. In this study, Lactiplantibacillus plantarum (formerly Lactobacillus plantarum; LP) was encapsulated in sodium alginate (SA)-resistant starch (RS)-epigallocatechin gallate (EGCG) matrices using extrusion to enhance stability and delivery. Microcapsules were characterized for encapsulation efficiency (EE); process yield (PY); morphology, texture, and physicochemical properties; and structural features were examined by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and x-ray diffraction (XRD). Storage stability was assessed for 90 days at 4°C and 25°C, and probiotic survival was evaluated under simulated GI conditions. Encapsulation produced high EE (up to approximately 97%) and PY (96% on average), and the presence of RS and EGCG enhanced the structural quality of the encapsulation matrix. SEM confirmed a compact and uniform surface in RS- and EGCG-based capsules, while FTIR and XRD indicated hydrogen bonding and reduced crystallinity. During storage, the SA-RS-EGCG matrix maintained > 8.0 log colony-forming unit (CFU)/g of LP at 4°C after 90 days, whereas free (unencapsulated) cells declined to < 3.5 log CFU/g. Under simulated digestion, free cells rapidly decreased, while SA-RS-EGCG retained approximately 85%-90% LP survival in gastric fluid and showed sustained release in intestinal fluid. These findings demonstrate that SA encapsulation provides an effective protective barrier for LP, whereas the incorporation of RS and EGCG further improves matrix structure, probiotic stability, and controlled release through complementary effects, highlighting the potential of this tri-component delivery system for functional food applications. PRACTICAL APPLICATIONS: The composite encapsulation system developed in this study offers a practical approach to enhancing the stability of probiotic bacteria in functional foods. Using sodium alginate, resistant starch, and EGCG polyphenol together enhances both shelf life and survival during digestion, supporting the development of more effective synbiotic products for the food industry.