Fermentation characteristics of Pixian broad bean paste in closed system of gradient steady-state temperature field

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.

Impacts of Aspergillus oryzae 3.042 on the flavor formation pathway in Cantonese soy sauce koji

To investigate the mechanism of flavor formation during the traditional preparation Cantonese soy sauce koji (TP), the changes of microorganisms, physicochemical properties, and flavor compounds in TP were comprehensively and dynamically monitored by absolute quantitative methods. Results demonstrated that inoculating Aspergillus oryzae 3.042 in TP was crucial role in enhancing enzyme activity properties. Absolute quantification of flavor combined with multivariate statistical analysis yielded 5 organic acids, 15 amino acids, and 2 volatiles as significantly different flavors of TP. Amplicon sequencing and RT-qPCR revealed that the dominant genera were Staphylococcus, Weissella, Enterobacter, Lactic streptococci, Lactobacillus, and Aspergillus, which exhibited a increasing trend in TP. Correlation analysis exhibited that Staphylococcus and Aspergillus were the pivotal genera contributing to the enzyme activities and flavor of TP. The flavor formation network involved lipid and protein degradation, carbohydrate metabolism and other pathways. Simultaneously, TP can appropriately increase the fermentation time to improve product quality.

Polymethoxylated flavones from the leaves of Vitex negundo have fungal-promoting and antibacterial activities during the production of broad bean koji

Broad bean paste is a popular condiment in Asian countries. Leaves of Vitex negundo Linn. were used extensively in China during the koji-making of broad bean paste. Spreading V. negundo leaves on raw broad beans during fermentation was able to facilitate the rapid growth of fungi to form mature koji. We isolated two strains of fungi from mature koji, and four strains of bacteria from the rotten broad beans resulting from a failed attempt. According to microbial activity assays, two polymethoxylated flavones, 5-hydroxy-3,6,7,8,3',4'-hexamethoxy flavone (HJ-1) and 5,4'-dihydroxy-3,6,7,8,3'-pentamethoxy flavone (HJ-2) were isolated from V. negundo leaves, and the fungal growth promotion and inhibition of bacterial growth of these two compounds were found to improve the production of broad bean koji. This study reveals the compounds present in V. negundo leaves with bioactivity against important microbes in koji manufacture, and provides a theoretical basis for the application of V. negundo in broad bean paste production.

Correlation Analysis between Microbial Communities and Flavor Compounds during the Post-Ripening Fermentation of Traditional Chili Bean Paste

Chili bean paste is a traditional flavor sauce, and its flavor compounds are closely related to its microflora. This study focused on investigating the content of bioactive compounds, flavor compounds, and microbial communities during the post-ripening fermentation of chili bean paste, aiming to provide a reference for improving the flavor of chili bean paste by regulating microorganisms. Compared to no post-ripening fermentation, the content of organic acids increased significantly (p < 0.05), especially that of citric acid (1.51 times). Glutamic acid (Glu) was the most abundant of the 17 free amino acids at 4.0 mg/g. The aroma profiles of the samples were significantly influenced by fifteen of the analyzed volatile compounds, especially methyl salicylate, methyl caproate, and 2-octanol (ROAV > 1). Latilactobacillus (27.45%) and Pseudomonas (9.01%) were the dominant bacterial genera, and Starmerella (32.95%) and Pichia (17.01%) were the dominant fungal genera. Weissella, Lacticaseibacillus, Pichia, and Kazachstania had positive effects on volatile flavoring compounds, which enriched the texture and flavor of the chili bean paste. Therefore, the microbial-community activity during the post-ripening fermentation is the key to enhance the flavor quality of the product.

A Systematic Comparative Study on the Physicochemical Properties, Volatile Compounds, and Biological Activity of Typical Fermented Soy Foods

Fermented soy foods can effectively improve the unpleasant odor of soybean and reduce its anti-nutritional factors while forming aromatic and bioactive compounds. However, a differential analysis of characteristic flavor and function among different fermented soy foods has yet to be conducted. In this study, a systematic comparison of different fermented soy foods was performed using E-nose, HS-SMPE-GC×GC-MS, bioactivity validation, and correlation analysis. The results showed that soy sauce and natto flavor profiles significantly differed from other products. Esters and alcohols were the main volatile substances in furu, broad bean paste, douchi, doujiang, and soy sauce, while pyrazine substances were mainly present in natto. Phenylacetaldehyde contributed to the sweet aroma of furu, while 1-octene-3-ol played a crucial role in the flavor formation of broad bean paste. 2,3-Butanediol and ethyl phenylacetate contributed fruity and honey-like aromas to douchi, doujiang, and soy sauce, respectively, while benzaldehyde played a vital role in the flavor synthesis of douchi. All six fermented soy foods demonstrated favorable antioxidative and antibacterial activities, although their efficacy varied significantly. This study lays the foundation for elucidating the mechanisms of flavor and functionality formation in fermented soy foods, which will help in the targeted development and optimization of these products.

Partial substitution of wheat flour with soybean and gluten powder: impact on flavor characteristics of Pixian Douban-Meju and its quality

BACKGROUND

In this study, different proportions of soybean flour and gluten flour were used as partial replacements for wheat flour for the fermentation of Pixian Douban-Meju (PXDB). The aim was to study the effects of soybean flour/gluten flour on the quality improvement of PXDB.

RESULTS

In comparison with the control group (CT) (0% substitution of wheat flour), substitution of wheat flower with 12.5% soybean flour (the H2 group), 7.5% gluten flour (G2), and 10% gluten flour (G3) improved the amino acid nitrogen content by 3.8%, 5.6%, and 9.4% respectively. The mixtures of wheat flour and gluten flour (G2 or G3) increased the organic acid and free amino acid content. The results of two-dimensional gas chromatography mass spectrometry (GC × GC-MS) showed that the amount of key aroma substances increased about sixfold in comparison with the CT group (194.61 g.kg-1 ), achieving 1283.67, 1113.883, and 1160.19 g.kg-1 in the H2, G2, and G3 groups, respectively. There were also more aldehydes and pyrazines in all the substitution groups. Quantitative descriptive analysis indicated that the G3 sample presented the best organoleptic quality with a reddish-brown color and a more mellow aroma than the control sample.

CONCLUSION

In conclusion, the fermentation of G3 resulted in higher quality PXDB-meju, showing that partial substitution of wheat flour with gluten improved the quality of PXDB. © 2023 Society of Chemical Industry.

Characterization of color, metabolites and microbial community dynamics of doubanjiang during constant temperature fermentation

This study aimed to elaborate the effect of temperature on doubanjiang fermentation. Two batches of constant-temperature groups were prepared and their physicochemical parameters, color formation, metabolites and microbial community dynamics during fermentation were determined and compared with those of natural temperature fermentation group. The results showed that fermentation at 40 °C could accelerate the accumulation of amino nitrogen, reducing sugar, amino acids, organic acids and various volatile metabolites while it was able to inhibit the growth of conditionally pathogenic bacteria, such as Klebsiella and Salmonella. However, high concentrations of total acids and biogenic amines, protrusive burnt flavor and darker color were observed in constant temperature fermentation, which were unfavorable for doubanjiang quality. Higher fermentation temperature lowered the diversity of bacterial community and favored the growth of Bacillus genus. The correlation between key microbial genera and doubanjiang quality indexes were significantly different among different temperatures. This study would deep our understanding of the roles of temperature ondoubanjiangfermentation.

Synergistic Fermentation with Functional Microorganisms Improves Safety and Quality of Traditional Chinese Fermented Foods

Traditional fermented foods are favored by people around the world for their positive health and taste advantages. Many of the fermented foods, including Chinese traditional fermented foods, are produced through mixed-culture fermentation. Apart from reducing the formation of harmful compounds such as ethyl carbamate (EC) and biogenic amines (BAs) during food fermentation, it is also difficult to precisely control and regulate the fermentation process based on the control of environmental conditions alone, due to the complex microbiota and an unclarified fermentation mechanism. In this review, key microorganisms involved in Chinese fermented foods such as baijiu, soy sauce, and vinegar production are elaborated, and relations between microbial composition and the aroma or quality of food are discussed. This review focuses on the interpretation of functions and roles of beneficial (functional) microorganisms that participate in food fermentation and the discussion of the possibilities of the synergistic use of functional microorganisms to improve the safety and quality of Chinese fermented foods. Conducting work toward the isolation of beneficial microorganisms is a challenge for modern food fermentation technology. Thus, methods for the isolation and mutagenesis of functional microbial strains for synergistic food fermentation are summarized. Finally, the limitations and future prospects of the use of functional microorganisms in traditional Chinese fermented foods are reviewed. This review provides an overview of the applications of synergistic fermentation with functional microorganisms in the improvement of the safety or sensory qualities of fermented foods.

HS-SPME-GC × GC/MS combined with multivariate statistics analysis to investigate the flavor formation mechanism of tank-fermented broad bean paste

With the advancement of industrialization, tank fermentation technology is promising for Pixian broad bean paste. This study identified and analyzed the general physicochemical factors and volatile metabolites of fermented broad beans in a thermostatic fermenter. Headspace solid-phase microextraction (HS-SPME)-two-dimensional gas chromatography-mass spectrometry (GC × GC-MS) was applied to detect the volatile compounds in fermented broad beans, while metabolomics was used to explore their physicochemical characteristics and analyze the possible metabolic mechanism. A total of 184 different metabolites were detected, including 36 alcohols, 29 aldehydes, 26 esters, 21 ketones, 14 acids, 14 aromatic compounds, ten heterocycles, nine phenols, nine organonitrogen compounds, seven hydrocarbons, two ethers, and seven other types, which were annotated to various branch metabolic pathways of carbohydrate and amino acid metabolism. This study provides references for subsequent functional microorganism mining to improve the quality of the tank-fermented broad beans and upgrade the Pixian broad bean paste industry.