Understanding the correlation between formation of flavor compounds and dominant bacteria during Luoyang mung bean sour fermentation

Abstract

To understand the change of the overall flavor component, including volatile compounds and free amino acid, Luoyang mung bean sour (LMBS) was investigated by gas chromatography-mass spectrometry (GC-MS) and automatic amino acid analyzer. The results showed that the beany flavor compounds, including hexanal, 2-hexenal, hexanol, and 1-octene-3-ol, significantly decreased or even disappeared. The concentration of esters and acids, represented by caproic acid and hexyl acetate, increased during LMBS fermentation. By detecting the free amino acids, it was found that the umami taste of glutamic acid (Glu) and aspartic acid (Asp) were the dominant amino acids. Among the 7 metabolites tested, lactic acid exhibited the highest concentration and continued to accumulate during fermentation. Leuconostoc, Enterobacter, Lactobacillus, Citrobacter Pediococcus, and Lactococcus were identified as the dominant bacterial groups that exhibited fluctuations during LMBS fermentation. Ultimately, Lactobacillus emerged as the dominant species. The network of Spearman correlation analysis was employed to uncover the relationship between bacterial community and flavor compounds during the fermentation of LMBS. For the dominant bacteria, Leuconostoc, Pediococcus, and Lactobacillus were positively correlated with acetic acid, lactic acid, citric acid, alcohol, sweet and umami amino acids, while negatively correlated with ketones alcohols and bitter amino acids.