Modulation of the volatile flavor compounds profile in low-salt spontaneously fermented yellow capsicum sauce by Lactiplantibacillus plantarum

Yellow capsicum sauce (YCS) is a special fermented condiment in Hainan province, China, and its fermentation typically occurs in a high-salt environment. In this study, the effects of different salt contents (5, 10, 15 and 20%, w/w) on microbial communities and volatile flavor profiles in YCS were systematically investigated by metagenomic approach and gas chromatography-mass spectrometry combined with solid phase microextraction technology. The results revealed that Lactiplantibacillus (54.66%) was the dominant lactic acid bacteria in low-salt samples (SF5), while Klebsiella emerged as the dominant bacterium in paste with higher salinity levels (SF15 and SF20). A total of 48 volatile flavor compounds (VFCs) were detected in the naturally fermented YCS, with alcohols and esters being the primary VFCs. Low-salt fermentation facilitated the accumulation of VFCs, and the total VFCs content in SF5 was the highest. According to Spearman correlation analysis, aroma compounds showed a strong correlation with Lactiplantibacillus plantarum . To further validate the findings, L. plantarum MA1 isolated from SF5 was inoculated into the low-salt YCS substrate for bioaugmented fermentation. This strain significantly increased key aroma components, such as cis -3-hexenyl isovalerate, hexyl 3-methylbutanoate, ethyl acetate and ethyl 4-methyl valerate. Moreover, it significantly increased the lactic acid content while reducing the nitrite content, thereby more effectively preserving the fresh yellow color of capsicum sauce and the stability of its spiciness.