Identification and validation of core microbes associated with key aroma formation in fermented pepper paste (Capsicum annuum L.)

Fermented peppers are usually obtained by the spontaneous fermentation of microorganisms attached to fresh peppers, and the variable microbial composition would lead to inconsistencies in flavor between batches. To demonstrate the roles of microorganisms in flavor formation, the core microbes closely associated with the key aroma compounds of fermented pepper paste were screened and validated in this study. Lactobacillus was the dominant bacterial genus in fermented pepper paste, whereas the main fungal genera were Alternaria and Kazachstania. Nine strains of the genera Lactobacillus, Weissella, Bacillus, Zygosaccharomyces, Kazachstania, Debaryomyces, and Pichia were isolated from fermented pepper paste. Eleven key aroma compounds were identified using gas chromatography combined with olfactometry and relative odor activity values. Correlation analysis showed that Zygosaccharomyces and Kazachstania were positively correlated with the majority of the key aroma compounds, whereas Lactobacillus was negatively correlated with them. Thus, Zygosaccharomyces and Kazachstania were identified as core genera associated with the key odorants. Finally, Zygosaccharomyces bis-porus, Kazachstania humilis, and Lactiplantibacillus plantarum were used as starter cultures for fermented peppers, confirming that Z. bisporus and K. humilis were more beneficial for the key aroma compounds (e.g., acetate, linalool, and phenyl ethanol) rather than L. plantarum. This study contributed to understanding the flavor for-mation mechanism and provided references for the quality control of food fermentation.

Automated summary

Microorganisms play a critical role in the flavor formation of fermented pepper paste. Lactobacillus, Alternaria, and Kazachstania were found to be the dominant bacterial and fungal genera in the paste. Zygosaccharomyces and Kazachstania were identified as core genera associated with key aroma compounds, while Lactobacillus had a negative correlation with them. This study contributes to the understanding of flavor formation and provides references for quality control in food fermentation.