Solid-state fermentation: Bioconversions and impacts on bioactive and nutritional compounds in oats

The nutritional value of oats can be enhanced through solid-state fermentation (SSF) to release otherwise tightly bound, inaccessible nutrients and bioactives. Extensive research has shown that SSF can liberate bioactive compounds from oats, such as phenolic compounds and peptides through modification of the microstructure. Studies also demonstrate that SSF enhances the bioactive properties of oats, including antioxidant, antidiabetic, anticancer, anti-inflammatory, and angiotensin-converting enzyme inhibitory. Additionally, SSF can modify the macronutrient and antinutritional components of oat substrates. In particular, the protein fraction can be enriched by SSF with filamentous fungi due to the inherently proteinous nature of their mycelium. Most SSF microorganisms can also reduce the antinutritional compounds in oats like tannins and phytic acid. Despite the breadth of SSF research for oat substrates, no review exists for oat specifically and more generally, and no review exists considering bioactive and nutritional aspects together. This review extensively discussed these facets. Future research avenues are explored and should provide insight into the microstructural modification of oats as a function of different fermentation conditions by leveraging advancements in imaging. Mechanistic and quantitative insight into how these structural changes and biotransformations influence the release of bioactive compounds (including the dynamic digestion process) should be explored. The molecular mechanism by which specific SSFed oat bioactive compounds (phenols and peptides) confer their biological effects requires further development. Combining analysis of the macronutrient and bioactive properties of solid-state-fermented oat substrates provides a more detailed picture of the overall nutritional value and health implications of solid-state fermented oat products.