Sodium caseinate and maltodextrin-based encapsulation improves viability and antimicrobial function of Lactiplantibacillus plantarum S61 during storage and simulated digestion

Probiotics such as Lactiplantibacillus plantarum S61 have demonstrated the ability to improve gut health and immune function when incorporated into functional foods. However, their viability is significantly challenged by environmental stresses encountered during processing, storage, and gastrointestinal transit. This study investigated the encapsulation of L. plantarum S61 using maltodextrin (MD) or in combination with sodium caseinate (CA-Na) as wall materials, employing both spray-drying (SD) and freeze-drying (FD) techniques under acidic (pH 3) and neutral (pH 7) conditions. The effectiveness of the encapsulation was assessed through physicochemical characterization, morphological analysis, resistance to simulated gastric and intestinal fluids, and storage stability at 4 °C over 12 weeks. Successful encapsulation was confirmed by FT-IR and SEM analyses, which revealed the entrapment of bacterial cells within the polymeric matrix. Across all formulations, incorporating sodium caseinate (CA‑Na) markedly increased encapsulation efficiency and enhanced probiotic viability during storage, while also significantly improving resistance to gastrointestinal stress. Notably, freeze‑dried powders prepared at pH 7 retained 6.235 log CFU/g after 3 hours in simulated gastric fluid, compared to just 3.931 log CFU/g for free cells. Moreover, encapsulation also enhanced the antifungal activity of L. plantarum S61 metabolites against Rhodotorula glutinis , reaching inhibition zones of 33.69 ± 0.22 mm in the optimized FD microcapsules with MD and CA-Na at pH 7. These findings highlight the potential of optimized encapsulation strategies to preserve the viability and bioactivity of probiotics for application in functional food formulations.