Red rice (Oryza sativa L.) is a pigmented cereal with nutritional, technological, and functional characteristics that can be influenced by the germination process. This study aimed to characterize raw red rice (RR) and germinated red rice (GRR) cultivated in the state of Paraíba (Northeastern region) - Brazil, regarding their nutritional composition, physicochemical properties, mineral and phenolic profiles, thermal behavior, antioxidant capacity, and impacts on bacterial groups comprising the human gut microbiota during in vitro colonic fermentation. RR and GRR exhibited nutritional and functional attributes, serving as sources of dietary fiber, minerals, fermentable substrates, and bioactive compounds. RR had higher contents of protein (7.21 g/100 g), soluble fiber (6.35 g/100 g), and antioxidant capacity (6.01 μmol Trolox/g – ABTS; 4.54 μmol FeSO₄/g - FRAP), as well as greater thermal stability. GRR was characterized by higher contents of fermentable sugars, including glucose (7.87 g/100 g), fructose (4.85 g/100 g), and maltose (3.55 g/100 g), higher contents of insoluble fiber (5.85 g/100 g), a distinct mineral composition, a predominance of malic, citric and lactic acids, and an enriched phenolic profile, notably featuring ferulic acid, p-coumaric acid, and procyanidins. During in vitro colonic fermentation, both RR and GRR promoted the growth of beneficial bacterial groups and stimulated the production of microbial metabolites, including acetic, propionic, butyric, and γ-aminobutyric acids, demonstrating their fermentability and potential to modulate intestinal microbial metabolism. These results provide a comprehensive characterization of red rice cultivated in Northeastern Brazil and support its potential application as a functional food ingredient beneficial to gut health.
