Survival of Lacticaseibacillus rhamnosus LRB in a Potential Synbiotic Oat Beverage: Insights into Cell-Matrix Interactions During In Vitro Digestion

Abstract The growing demand for plant-based functional foods has positioned oats as a promising matrix for developing synbiotic products, given their high fiber content. This study aimed to develop a fermented oat beverage supplemented with inulin to evaluate the survival and morphological integrity of Lacticaseibacillus rhamnosus LRB during in vitro gastrointestinal digestion. A bovine milk beverage with the same added ingredients served as a reference matrix (control). The oat beverage reached the target pH (~ 4.5) faster than the bovine milk beverage and maintained the stability of the L. rhamnosus LRB during 28 days of storage (8.34 ± 0.02 log cfu.mL − 1 ; ∆ log = -0.27). After simulated in vitro digestion, the oat matrix ensured high recovery rates (> 7 log cfu.mL − 1 ). Flow cytometry revealed a significantly lower percentage of dead cells in the oat beverage (2.10%) during the gastric digestion phase. Scanning electron microscopy confirmed the structural stress induced by digestion in the lactic acid culture. Additionally, the oat beverage maintained substantial antioxidant activity in the intestinal digested fraction. These results demonstrate that the oat-inulin matrix is a technologically viable vehicle for L. rhamnosus LRB, providing more than 10 log cfu per serving and meeting the criteria for potential probiotic food. This study elucidates the protective role of the oat matrix and supports the development of high-performance plant-based functional beverages.