Effect of salt concentration on chemical profiles and microbial communities of fermented cowpea

Fermented cowpea is one of the important fermented vegetables in China and is widely consumed in China, especially in the south of China. However, up to now, the study of bacteria communities and flavor compounds in fermented cowpea is few, especially the impact of salt on the microbial structure and dynamic changes of metabolites of cowpea. Therefore, this study investigated the effects of four salt concentrations (0 %, 3 %, 6 %, 9 %) on the microbial structure and metabolites of fermented cowpea. Results showed that the ethyl acetate, linalool, benzyl alcohol, 3-methyl butyric acid, 2-methyl butyric acid, phenylethanol, acetic acid, 2-octanone, 3-methyl-1-butanol acetate and 1-octen-3-ol contributed significantly to cowpea flavor compounds. Lactobacillus, Acinetobacter, Pseudomonas, Muribaculaceae, Bacteroides, etc., were the main genera in fermented cowpea. In addition, two-way orthogonal partial least squares (O2PLS) showed that there was a potential correlation between 8 bacterial genera (including Lactobacillus, Clostridium_sensu_stricto_1, Prevotella_9, Caproiciproducens, Bacillus, Lysinibacillus, Burkholderia-Caballeronia-Paraburkholderia, Pseudomonas, Acinetobacter, Terribacillus) and 10 characteristic flavor compounds, which was considered to have an important impact on flavor substances. Results showed that salinity not only affects microorganisms, but also affects flavor. In addition, the chemical profiles and bacterial communities of 3 % salt fermented cowpea were similar to those of 6 % fermented cowpea. Considering the cost, 3% salt was selected to ferment cowpea in future.