Microstructural changes during solid-state fermentation of oats influence nutrient digestibility and bioactive properties.

Solid-state fermentation (SSF) can enhance the nutritional functionality of oat-based ingredients. This study investigated the effect of three oat SSF systems on microstructure, digestibility and bioactive properties. Ground and autoclaved oat substrate was fermented for 0, 48, and 120 h using mono-cultures of Lactiplantibacillus plantarum or Rhizopus oligosporus, or their co-culture under their respective incubation conditions. Phytic acid and increased l-serine equivalents increased under the R. oligosporus mono- and co-culture SSF conditions, whereas limited compositional change occurred under Lp. plantarum mono-culture SSF conditions. Microstructural disruption occurred earlier in R. oligosporus-containing SSF systems, but became extensive across systems with prolonged fermentation. Distinct digestibility responses were observed, including reduced starch digestion rates under Lp. plantarum mono-culture conditions and altered starch and protein accessibility under R. oligosporus-containing SSF conditions. SSF also enhanced apparent in vitro phenolics and antioxidant activity, demonstrating system- and time-dependent modification of functionality in fermented oats.