Organic acids drove the microbiota succession and consequently altered the flavor quality of Laotan Suancai across fermentation rounds: Insights from the microbiome and metabolome.

Laotan Suancai, a popular traditional Chinese fermented vegetable, is manufactured in the industry via four fermentation rounds. However, the differences in flavor quality of Laotan Suancai from the four fermentation rounds and the causes of this variation remain unclear. Metabolome analysis indicated that the different content of five taste compounds and 31 aroma compounds caused the differences in flavor quality among the variated fermentation rounds of Laotan Suancai. Amplicon sequencing indicated that the microbial succession exhibited a certain pattern during four fermentation rounds and further analysis unveiled that organic acids drove the microbiota shift to more acid-resistant populations. Spearman correlation analysis highlighted that seven core microbes may be involved in the formation of differential flavor and the corresponding metabolic pathways were reconstructed by function prediction. Our findings offer a novel perspective on comprehending the deterioration of flavor quality across the fermentation rounds of Laotan Suancai.

Integrated metatranscriptomics and metabolomics reveal microbial succession and flavor formation mechanisms during the spontaneous fermentation of Laotan Suancai.

Laotan Suancai, a Chinese traditional fermented vegetable, possesses a unique flavor that depends on the fermentative microbiota. However, the drivers of microbial succession and the correlation between flavor and active microbiota remain unclear. A total of 21 characteristic flavor metabolites were identified in Laotan Suancai by metabolomics, including 8 sulfides, 6 terpenes, 3 organic acids, 2 isothiocyanates, 1 ester, and 1 pyrazine. Metatranscriptome analysis revealed variations in the active microbiota at different stages of fermentation, and further analysis indicated that organic acids were the primary drivers of microbial succession. Additionally, we reconstructed the metabolic network responsible for the formation of characteristic flavor compounds and identified Companilactobacillus alimentarius, Weissella cibaria, Lactiplantibacillus plantarum, and Loigolactobacillus coryniformis as the core functional microbes involved in flavor development. This study contributed to profoundly understanding the relationship between the active microbiota and flavor quality formation, as well as the targeted selection of starters with flavor regulation abilities.

Dynamic analysis of flavor properties and microbial communities in Chinese pickled chili pepper (Capsicum frutescens L.): A typical industrial-scale natural fermentation process.

Pickled chili pepper (Capsicum frutescens L.), a traditional Chinese fermented vegetable product, is favored by consumers because of its unique flavor. Microbial succession is the main factor affecting the development of the typical flavor of pickled chili pepper. This study investigated the dynamics of flavor changes (mouthfeel sensation, taste properties, and aroma profile) and microbial diversity (bacterial and fungal communities) during the industrial-scale fermentation of pickled chili pepper. Results revealed that during fermentation, the hardness and pungency of pickled chili pepper decreased significantly (P < 0.05), whereas organic acids, free amino acids, and volatiles (especially terpenes, alcohols, and aldehydes) increased significantly (P < 0.05). Lactobacillus and Candida species, specifically, Lactobacillus brevis and Candida sp. F15, dominated in pickled chili pepper. Correlation analysis indicated that the dominant bacterial (Lactobacillus versmoldensis and L. brevis) and fungal (Colletotrichum simmondsii and Cladosporium tenuissimum) species had a high positive correlation with volatile compounds (e.g., aldehydes, terpenes, and esters).

Dynamics of microbial communities, flavor, and physicochemical properties of pickled chayote during an industrial-scale natural fermentation: Correlation between microorganisms and metabolites.

Pickled chayote is a Chinese fermented vegetable with unique flavors and is favored by local consumers. However, little is known about its quality changes and microbial community succession during fermentation and the relationship between microbes and quality. In the work, the physicochemical quality attributes (pH, acidity, nitrite, texture, and color) and flavor properties (sugars, organic acids, free amino acid [FAA], and volatiles) were investigated. The results revealed that organic acids, FAAs, and key volatiles (esters, terpenes, alcohols, and phenols) significantly increased during fermentation. Lactobacillus was the dominant bacterial genus with Lactobacillus alimentarius being the prevalent species; Kazachstania and Pichia were dominant fungal genera with Kazachstania humilis and Pichia membranifaciens being the prevalent species. The microbial metabolic network found that bacteria (L. alimentarius, L. futsaii, and L. paralimentarius) and fungi (K. humilis and P. membranifaciens) played significant roles in the physicochemical changes and flavor production of pickled chayote.

Effect of ripening and variety on the physiochemical quality and flavor of fermented Chinese chili pepper (Paojiao).

This work monitored the effect of ripening and variety on the physiochemical quality and flavor of fermented Chinese chili pepper (Paojiao). Three commercial varieties of chili pepper (Capsicum frutescens Linn.) at three ripening stages were selected. Physiochemical quality (color, texture, and vitamin C) and flavor properties [capsaicinoids, free amino acid (FAA), and aroma] were determined and compared by multivariate data analysis. The hardness and chewiness decreased, while the contents of vitamin C, capsaicin, and taste-active FAAs increased in Paojiao with ripening. More volatiles were found in green peppers. Fingerprinting and multivariate data analysis revealed that ester, aldehydes, and terpenes were discriminant volatiles that significantly changed in Paojiao during ripening. In general, ripening and variety greatly affect the physiochemical and flavor quality of peppers and their effects intensify after fermentation.