Alginate-Grape Pomace Flour Microcapsules for Enhanced Protection and Delivery of Lacticaseibacillus rhamnosus GG

The incorporation of plant-derived fibers as co-encapsulating agents has emerged as a strategy to improve probiotic stability and functionality. This study evaluated grape pomace flour (GF) as a co-encapsulant in sodium alginate (SA) based microcapsules containing Lacticaseibacillus rhamnosus GG, focusing on structural properties, thermal resistance, antioxidant activity, gastrointestinal survival, and viability in orange juice. High encapsulation efficiencies were obtained for alginate (94.80%) and alginate-GF systems (91.13%), with viable counts above 8.3 log CFU/mL. FTIR, DSC, and TGA analyses demonstrated molecular interactions between alginate and GF, resulting in modified thermal transitions and enhanced matrix cohesion. SA/GF microcapsules showed improved refrigerated stability, maintaining ≥ 8.0 log CFU/mL after 28 days at 4 °C, whereas free cells declined to 3.3-4.0 log CFU/mL. During rapid pasteurization (72 °C/15 s), SA/GF capsules preserved 11 log CFU/g, compared to 7.15 log CFU/g in alginate-only capsules, while free cells were completely inactivated. Under simulated gastric conditions, SA/GF capsules maintained 8.60-9.19 log CFU/g, whereas alginate-only capsules decreased to 5.94 log CFU/g after 90 min, and free cells became undetectable after 120 min. In simulated intestinal juice, SA/GF capsules recovered to 9.45 log CFU/g at 120 min. In orange juice, free cells showed > 2.5 log reduction within 3 days, while encapsulated formulations exhibited reductions < 1 log over 9 days (p ≤ 0.05). Overall, GF reinforced the alginate matrix, reduced microbial inactivation, and improved probiotic resistance and survival, supporting its application as a sustainable co-encapsulant in functional foods.