Western Sichuan Yi suancai contains a group of highly functional microorganisms in an alpine and high-altitude ecological environment. Due to its unique salt-free fermentation process, it is nutritious and has a crispy texture. Six periods were established during fermentation: day 0, day 2, day 5, day 8, day 11, and day 14. The results showed that the antioxidant capacity and organic acid content increased during the fermentation process, while the pH gradually decreased, indicating that suancai from the later periods was better for supplementing the human body with acid substances and eliminating free radicals. Twenty-six flavour compounds were identified, including alcohols, esters, ketones, and acids. Ethyl alcohol, 3-methyl-1-butanol, ethyl methanoate, and acetic acid were the main contributors to the flavour, imparting floral and fruity notes to the suancai. Five dominant bacterial genera (Lactobacillus, Leuconostoc, Weissella, Klebsiella, and unclassified_o__Lactobacillales) were identified via high-throughput sequencing during the fermentation process, and there were nine dominant fungal genera (Dipodascaceae_gen_Incertae_sedis, Mucor, Pichia, unclassified__f__Dipodascaceaet, Cyberlindnera, Diutina, Trichosporon, Saccharomycopsis, and Wickerhamomyces). Correlation analysis showed that the antioxidant capacity was positively correlated with genera such as Lactobacillus, Mucor, and Alternaria, indicating that these microorganisms have important roles in enhancing the antioxidant properties of suancai. Meanwhile, some genera, such as Microbacterium, Herbaspirillum, Mortierella, and Sampaiozyma, promote the synthesis of alcohols, esters, acids, and ketones. This study revealed the interactions between microorganisms and metabolites during the fermentation of western Sichuan Yi suancai and provided a scientific basis for further understanding the fermentation mechanism of traditional suancai and improving the fermentation process.
