Volatile evolutions during solid-state fermentation of oats by mono- and co-cultures: A Flavoromic approach using classical chemometric and machine learning techniques.

While solid-state fermentation (SSF) can enhance the bioactive potential of oats, the temporal dynamics of volatile compound formation, particularly in mixed microbial systems, remain poorly characterized. Such volatiles contribute not only to sensory attributes but also reflect underlying metabolic interactions during fermentation. This study investigated volatile evolution in oat SSF with Rhizopus oligosporus in mono-culture and co-culture with Lactiplantibacillus plantarum over 120 h. Fifty-five volatile compounds spanning ten chemical classes were identified. With the exception of aldehydes, most classes increased over time, with the co-culture producing higher levels of alcohols, carboxylic acids, esters, and ketones. Branched-chain, Strecker aldehyde peaks decreased during SSF in the co-culture system, indicating complementary metabolic exchange. Non-linear random forest regression better captured volatile trajectories than linear partial least squares regression. Together, these results provide a SSF system-level fingerprint of how mono- and co-culture SSF differentially shape oat volatile profiles, informing future development of fermented oat products.