Flavor development in vacuum dry-salted cowpeas: changes in volatile compounds and non-volatile metabolites during fermentation

Abstract

Flavor development in vacuum dry-salted cowpeas remains insufficiently understood despite the increasing use of this low-free-brine fermentation process. This study combined microbial profiling, volatile analysis, and untargeted metabolomics to characterize flavor formation during 21 days of fermentation. The results showed a clear transition from green-note volatiles to fermentation-associated aroma compounds, together with marked changes in microbial communities and non-volatile metabolites. Lactiplantibacillus became dominant, while yeast-like fungi increased mainly in the middle and late stages. Hexanal, 2-hexenal, and (Z)-3-hexen-1-ol decreased, whereas phenylethyl alcohol, 4-ethylphenol, esters, acids, ketones, and lipid-derived volatiles accumulated. Eleven volatile compounds were identified as candidate markers of flavor transition. Metabolomic analysis indicated changes in carbohydrates, amino acid derivatives, organic acids, peptides, benzenoids, and lipid-related metabolites. These findings highlight the importance of monitoring aroma compounds and precursor metabolites for regulating flavor quality in vacuum dry-salted fermented cowpeas.