Fermentation unlocks the nutritional potential of oat milk during in vitro dynamic gastrointestinal digestion and colonic fermentation.

Fermentation represents an effective bioprocessing strategy to enhance digestive properties and gut-health benefits of plant-based (oat) milk. Using combined in vitro gastrointestinal digestion and colonic fermentation, this study systematically investigated the impact of fermentation on oat milk's gastric emptying behavior, protein digestion kinetics, and gut microbiota modulation, with cow milk as a reference. Fermented oat milk delayed gastric emptying and increased protein digestibility from below 80% to 87.73%. This enhanced proteolysis improved essential/total amino acid bioaccessibility and liberated a diverse spectrum of bioactive peptides with health-promoting potential. Oat milk fermentation also modulated the colonic microbial community, specifically enriching beneficial lactic acid bacteria, while suppressing undesirable sulfate-reducing bacteria (Fusobacterium, Desulfovibrio). Fermentation boosted total short-chain fatty acid (SCFA) production to levels exceeding cow milk, while reducing branched-chain fatty acids (BCFA). These findings demonstrate that fermentation substantially improves the nutritional and gut-modulatory properties of oat milk under simulated digestive conditions.