Rice varieties affect bacterial diversity, flavor, and metabolites of zha-chili

Insights into the flavor contribution, mechanisms of action, and future trends of coagulase-negative staphylococci in fermented meat products: A review

During fermentation, meat is pre-treated and cured to cultivate a diverse microflora, resulting in fermented meat products with distinctive flavors. Coagulase-negative staphylococcus holds a crucial role in all fermented meat products, contributing to the breakdown of proteins, carbohydrates, and fats, and the creation of flavor compounds. Fermentation technology has important research value and significance in fermented meat products. The optimization and improvement of flavor by CNS can be achieved by regulating the fermentation environment, initial microflora and processing conditions. The review explores the ways in which coagulase-negative staphylococci contribute to the flavors in fermented meat products. The mechanism of flavor substance formation and means of regulation in coagulase-negative staphylococci were also investigated. The review concludes by summarizing future development trends and drawing conclusions.

Impact of ultra-high-pressure treatment on microbial community composition and flavor quality of jujube juice: Insights from high-throughput sequencing technology, intelligent bionic sensory system, and metabolomics approach

Ultra-high-pressure (UHP1) technology for cold pasteurization is a viable alternative to traditional heat sterilization for preserving food nutrients and flavor compounds during fruit juice processing. In this study, cutting-edge techniques, including high-throughput sequencing technology, intelligent bionic sensory systems, and metabolomics, were used to examine the impact of UHP treatment on microbial community composition, odor, and taste quality of jujube juice. The UHP treatment demonstrated its effect by inducing a reddish-yellow color in the jujube juice, thereby enhancing its brightness, overall color, and stability. The most significant enhancement was observed at 330 MPa. The microorganisms responsible for spoilage and deterioration of jujube juice during storage were categorized into three clusters: bacterial clusters at 0-330 MPa, 360-450 MPa, and 480-630 Mpa. The results showed no distinct distribution patterns for fungi based on the pressure strength. The dominant bacterial genera were Lactobacillus, Nocardia, Achromobacter, Enterobacter, Pseudomonas, Mesorhizobium, and Rhodococcus, whereas the dominant fungal genera were yeast and mold. Notably, Lactobacillus, Achromobacter, Enterobacter, and Pseudomonas were responsible for the significant differences between the 360 MPa to 450 MPa and 480 MPa to 630 MPa clusters in terms of bacterial spoilage, whereas Torulaspora, Lodderomyces, Wickerhamomyces, and Fusarium were the primary fungal spoilage genera. UHP treatment exerted no significant impact on the taste of jujube juice but influenced its sourness. Treatment at 330 MPa had the most pronounced effect on the presence of aromatic compounds and other odorants, which were substantially increased. Further analysis revealed the prevalence of organic acids, such as malic acid, succinic acid, and tartaric acid, in jujube juice and demonstrated a consistent relationship between changes in organic acids and sourness. In addition, nine distinct odorants with VIP values greater than 1 were identified in the jujube juice. Among these, methyl acetate and methyl caproate exhibited substantial increases following the UHP treatment at 330 MPa.

Kimchi Lactic Acid Bacteria Starter Culture: Impact on Fermented Malt Beverage Volatile Profile, Sensory Analysis, and Physicochemical Traits

Starter cultures used during the fermentation of malt wort can increase the sensory characteristics of the resulting beverages. This study aimed to explore the aroma composition and flavor recognition of malt wort beverages fermented with lactic acid bacteria (Levilactobacillus brevis WiKim0194) isolated from kimchi, using metabolomic profiling and electronic tongue and nose technologies. Four sugars and five organic acids were detected using high-performance liquid chromatography, with maltose and lactic acid present in the highest amounts. Additionally, e-tongue measurements showed a significant increase in the sourness (AHS), sweetness (ANS), and umami (NMS) sensors, whereas bitterness (SCS) significantly decreased. Furthermore, 20 key aroma compounds were identified using gas chromatography-mass spectrometry and 15 key aroma flavors were detected using an electronic nose. Vanillin, citronellol, and β-damascenone exhibited significant differences in the flavor profile of the beverage fermented by WiKim0194, which correlated with floral, fruity, and sweet notes. Therefore, we suggest that an appropriate starter culture can improve sensory characteristics and predict flavor development in malt wort beverages.

Characterization and correlation analysis of microbial flora and flavor profile of stinky acid, a Chinese traditional fermented condiment

To explore the microbial diversity and flavor profiles of stinky acid, we utilized high-throughput sequencing, culture-based techniques, and bionic E-sensory technologies. The results revealed a significant correlation between the acidity levels of stinky acid and the richness of its microbial community. Ten core bacterial genera and three core fungal genera exhibited ubiquity across all stinky acid samples. Through E-nose analysis, it was found that sulfides constituted the principal odor compounds responsible for stinky acid's distinct aroma. Further insights arose from the correlation analysis, indicating the potential contribution of Debaryomyces yeast to the sour taste profile. Meanwhile, three genera-Rhizopus and Thermoascus and Companilactobacillus-were identified as contributors to aromatic constituents. Interestingly, the findings indicated that Rhizopus and Thermoascus could reduce the intensity of the pungent odor of stinky acid. In summary, this investigation's outcomes offer new insights into the complex bacterial diversity of stinky acid.

Relationship between the Dynamics of Flavor Compounds and Microbial Succession in the Natural Fermentation of Zhalajiao, a Popular Traditional Chinese Fermented Chili Paste

Zhalajiao, a traditional Chinese fermented food, is popular due to its unique flavor. Traditional Zhalajiao fermentation is closely related to flavor compounds production. However, the mechanisms underlying the formation of these crucial flavor components in Zhalajiao remain unclear. Here, we explored the dynamic changes in physical and chemical properties, microbial diversity, and flavor components of Zhalajiao at various fermentation times. In total, 6 organic acids, 17 amino acids, and 21 key volatile compounds were determined as flavor components. In Zhalajiao, Lactobacillus and Cyanobacterium were the main bacteria that were involved in the formation of crucial flavor compounds. Candida showed a significant correlation with 14 key flavor compounds during fermentation (p < 0.05) and was the main fungal genus associated with flavor formation in Zhalajiao. This research offers a theoretical foundation for the flavor regulation and quality assurance of Zhalajiao.

Exploring metabolic dynamics during the fermentation of sea buckthorn beverage: comparative analysis of volatile aroma compounds and non-volatile metabolites using GC-MS and UHPLC-MS

Sea buckthorn has a high nutritional value, but its sour taste and foul odor make it unpalatable for consumers. In this study, we analyzed the metabolite changes occurring during the yeast-assisted fermentation of sea buckthorn juice using the HeadSpace Solid-Phase Microextraction Gas Chromatography-Mass Spectrometry (HS-SPME-GC-MS) and Ultra-High Performance Liquid Chromatography-Mass Spectrometry (UHPLC-MS) techniques. A total of 86 volatile aroma compounds were identified during the fermentation process. The content of total volatiles in sea buckthorn juice increased by 3469.16 μg/L after 18 h of fermentation, with 22 compounds showing elevated levels. Notably, the total content of esters with fruity, floral, and sweet aromas increased by 1957.09 μg/L. We identified 379 non-volatile metabolites and observed significant increases in the relative abundance of key active ingredients during fermentation: glycerophosphorylcholine (increased by 1.54), glutathione (increased by 1.49), L-glutamic acid (increased by 2.46), and vanillin (increased by 0.19). KEGG pathway analysis revealed that amino acid metabolism and lipid metabolism were the primary metabolic pathways involved during fermentation by Saccharomyces cerevisiae. Fermentation has been shown to improve the flavor of sea buckthorn juice and increase the relative content of bioactive compounds. This study provides novel insights into the metabolic dynamics of sea buckthorn juice following yeast fermentation through metabolomics analysis. These findings could serve as a theoretical foundation for further studies on the factors influencing differences in yeast fermentation.

Effect of Sichuan Pepper (Zanthoxylum genus) Addition on Flavor Profile in Fermented Ciba Chili (Capsicum genus) Using GC-IMS Combined with E-Nose and E-Tongue

This study examined the flavor profiles of fermented Ciba chili, comparing samples with Sichuan pepper (HJ) to those without Sichuan pepper (CK), using three analytical techniques: E-tongue, E-nose, and gas chromatography-ion mobility spectrometry (GC-IMS). The results obtained from the E-tongue and E-nose exhibited a clear difference in taste and flavor between CK and HJ. In detail, CK mainly exhibited a sour flavor profile, whereas HJ displayed an intricate and rich flavor. The HS-GC-IMS results identified a total of 60 compounds in the samples, with terpenes, alcohols, and esters being the primary volatile flavor compounds. Additionally, Zanthoxylum was found to significantly enhance the concentration of these compounds in fermented Ciba chili. Through robust principal component analysis (rPCA), 17 distinct flavor compounds were selected. Correlation analysis revealed that most terpenes exhibited positive correlations with LY2/LG, LY2/gCT1, LY2/Gct, LY2/G, LY2/Gh, and terpenes were found in higher concentrations in HJ. This study contributes a theoretical basis and provides data support for optimizing the fermentation process and elucidating the underlying mechanism of characteristic aroma formation in Ciba chili after fermentation.

Bacterial diversity and its correlation with sensory quality of two types of zha-chili from Shennongjia region, China

In the Shennongjia region of China, two types of zha-chili with distinct flavors exist: the first type (P zha-chili) uses a significant amount of chili pepper but no potato, while the other (PP zha-chili) contains a smaller amount of chili pepper but a proportion of potato. In order to investigate the bacterial diversity and sensory properties of these two types of zha-chili, this study employed a combination of amplicon sequencing, culture-based methods, and sensory technology. The results of the study showed statistically significant differences (P < 0.05) in bacterial diversity and communities between the two types of zha-chili. In particular, four dominant lactic acid bacteria (LAB) genera - Lactiplantibacillus, Lactococcus, Leuconostoc, and Weissella - were significantly enriched in PP zha-chili. The findings suggest that the proportions of chili pepper and potato can influence the bacterial diversity and content of LAB, with a higher proportion of chili pepper potentially inhibiting the growth of harmful species within the Enterobacteriaceae family. The study also used culture-based methods to identify the most dominant bacteria in the zha-chili samples as Lactiplantibacillus plantarum group, Companilactobacillus alimentarius, and Lacticaseibacillus paracasei. Correlation analysis indicated that LAB likely plays a significant role in shaping the aroma profile of zha-chili, with Levilactobacillus, Leuconostoc, Lactiplantibacillus, and Lactococcus showing correlation with E-nose sensory indices. However, these LAB were not significantly correlated with the taste properties of zha-chili. The study provides new insights into the influence of chili pepper and potato on the microbial diversity and flavor properties of zha-chili, and also presents potential LAB isolates for future research on zha-chili.

Evaluating the effect of lactic acid bacteria fermentation on quality, aroma, and metabolites of chickpea milk

Legumes are an attractive choice for developing new products since their health benefits. Fermentation can effectively improve the quality of soymilk. This study evaluated the impact of Lactobacillus plantarum fermentation on the physicochemical parameters, vitamins, organic acids, aroma substances, and metabolites of chickpea milk. The lactic acid bacteria (LAB) fermentation improved the color, antioxidant properties, total phenolic content, total flavonoid content, lactic acid content, and vitamin B6 content of raw juice. In total, 77 aroma substances were identified in chickpea milk by headspace solid-phase microextraction with gas chromatography/mass spectrometry (HS-SPME-GC-MS); 43 of the 77 aroma substances increased after the LAB fermentation with a significant decrease in beany flavor content (p < 0.05), improving the flavor of the soymilk product. Also, a total of 218 metabolites were determined in chickpea milk using non-targeted metabolomics techniques, including 51 differentially metabolites (28 up-regulated and 23 down-regulated; p < 0.05). These metabolites participated in multiple metabolic pathways during the LAB fermentation, ultimately improving the functional and antioxidant properties of fermented soymilk. Overall, LAB fermentation can improve the flavor, nutritional, and functional value of chickpea milk accelerating its consumer acceptance and development as an animal milk alternative.

Characterization of two novel pentose-fermenting and GABA-producing species: Levilactobacillus tujiorum sp. nov. and Secundilactobacillus angelensis sp. nov. Isolated from a solid-state fermented zha-chili

Lactobacilli are dominant in zha-chili. This study provides a taxonomic characterization of five bacterial strains isolated from zha-chili in China. The cells were Gram-positive, facultative anaerobic, non-spore-forming, flagella-free, catalase-negative, heterofermentative, pentose-fermenting, and gamma-aminobutyric acid (GABA)-producing rods. For HBUAS51241T, HBUAS51329, and HBUAS51416, C16:0, C18:1ω9c and C19:0 iso were the predominant cellular fatty acids; diphosphatidylglycerol (DPG), phosphatidylglycerol (DP), glycolipids (GL), and glycolipids (AL) were the major phospholipids. While for HBUAS51383T and HBUAS58055, C16:0, C18:1ω9c, C19:0 cyclo ω8c were the predominant cellular fatty acids; DPG, DP, GL, and AL were the major phospholipids. Strains HBUAS51241T, HBUAS51329, and HBUAS51416 showed 98.1-99.1% 16S rRNA gene sequence similarity, 80.2-81.4% ANI, 87.7-90.0% AAI, and 23.8-32.8% digital DDH to their closest related type strains Levilactobacillus hammesii DSM 16381T, Levilactobacillus parabrevis ATCC 53295T, and Levilactobacillus fuyuanensis 244-4T. Strains HBUAS51383T and HBUAS58055 showed 98.7-99.5% 16S rRNA gene sequence similarity, 75.4-81.4% ANI, 75.5-89.1% AAI, and 19.7-24.0% digital DDH to their closest related type strains Secundilactobacillus silagincola IWT5T, Secundilactobacillus silagei JCM 19001T, Secundilactobacillus pentosiphilus IWT25T, Secundilactobacillus mixtipabuli IWT30T, Secundilactobacillus odoratitofui DSM 19909T, and Secundilactobacillus similis DSM 23365T. The central carbon metabolism pathways for the five strains were summarizeded. Based on the phenotypic, chemotaxonomic, and genomic data, we propose two novel species Levilactobacillus tujiorum sp. nov. whose type strain is HBUAS51241T (=GDMCC 1.3022T = JCM 35241T), and Secundilactobacillus angelensis sp. nov. whose type strain is HBUAS51383T (=GDMCC 1.3021T = JCM 35209T).

Exploring the Dynamic of Bacterial Communities in Manila Clam (Ruditapes philippinarum) During Refrigerated Storage

Microorganism contamination is one of the most important factors affecting the spoilage and food safety of Manila clams. This study aimed to gain insights into bacterial composition and the dynamic change of bacterial communities on retailed Manila clam during refrigerated storage within the edible period. High-throughput sequencing was conducted to monitor the bacterial population with the prolongation of storage time of Day 0, Day 1, and Day 3. Result demonstrated that phyla of Proteobacteria, Actinobacteriota, Acidobacteriota, and Chloroflexi composed the majority of bacterial communities during the whole observation process. Furthermore, the increase of Proteobacteria showed a positive correlation with the storage time, whereas Acidobacteriota and Chloroflexi continued to decline in storage. For genus annotation, none of genus obtained dominant population in storage. From Day 0 to Day 1, the genera of Streptomyces, Bradyrhizobium, and Mycobacterium significantly increased; meanwhile, 12 genera significantly decreased. Compared with samples at Day 0, a total of 15 genera significantly decreased with the reduced proportion ranging from 0.50 to 4.40% at Day 3. At the end of the storage, the genus Crossiella became the most redundant population. Both the richness and diversity decreased at the start of storage at Day 1, and then slightly increased at Day 3 was observed. Based on the result in this study, strategy targeting the increased bacteria could be tested to improve the consumption quality and safety of refrigerated clam.

Bacterial Diversity, Organic Acid, and Flavor Analysis of Dacha and Ercha Fermented Grains of Fen Flavor Baijiu

Fen flavor Baijiu needs two rounds of fermentation, which will obtain Dacha after initial fermentation and Ercha after secondary fermentation. The quality of Baijiu is closely related to the microbes within fermented grains. However, the bacterial diversity in Dacha and Ercha fermented grains of Fen flavor Baijiu has not been reported. In the present study, the structure and diversity of bacteria communities within fermented grains of Fen flavor Baijiu were analyzed and evaluated using MiSeq platform's HTS with a sequencing target of the V3-V4 region of the 16S rRNA gene. Through the analysis of physical and chemical indexes and electronic senses, the relationship between bacterial flora, organic acid, taste, and aroma in fermented grains was clarified. The results indicated that Lactobacillus was the main bacteria in Dacha, and the mean relative content was 97.53%. The bacteria within Ercha samples were Pseudomonas and Bacillus, mean relative content was 37.16 and 28.02%, respectively. The diversity of bacterial communities in Ercha samples was significantly greater than that in Dacha samples. The correlation between Lactobacillus and organic acids, especially lactic acid, led to the difference between Dacha and Ercha organic acids, which also made the pH value of Dacha lower and the sour taste significantly higher than Ercha. Lactobacillus was significantly positively correlated with a variety of aromas, which made Dacha the response value of aromas higher. In addition, Bacillus had a significant positive correlation with bitterness and aromatic compounds, which led to a higher response value of bitterness in Ercha and made it present an aromatic aroma. This study provides an in-depth analysis of the difference between different stages of Fen flavor Baijiu, and theoretical support for the standard production and improvement in quality of Fen flavor Baijiu in the future.

Bacterial Communities and Prediction of Microbial Metabolic Pathway in Rice Wine Koji From Different Regions in China

Rice wine koji, a traditional homemade starter culture in China, is nutritious and delicious. The final quality of rice wine koji is closely related to the structure of its microbial community. However, the diversity of natural microorganisms in rice wine koji from different regions has not been evaluated. In this study, the microbial population of 92 naturally fermented rice koji samples collected from Hubei, Guangxi, and Sichuan was systematically analyzed by high-throughput sequencing. From all the rice wine koji samples, 22 phyla and 479 bacterial genera were identified. Weissella, Pediococcus, Lactobacillus, Enterobacter, Lactococcus, Pantoea, Bacillus, Staphylococcus, and Leuconostoc were the dominant genera in rice wine koji. The bacterial community structure of rice wine koji samples from different regions was significantly different (p < 0.05). The bacterial community composition of the samples from Hubei and Guangxi was similar, but significantly different from that of SC samples (p < 0.05). These differences may be caused by variations in geography, environment, or manufacturing. In addition, the results of microbial phenotype prediction by BugBase and bacterial functional potential prediction by PICRUSt showed that eight of the nine predicted phenotypic functions of rice wine koji samples from different regions were significantly different (p < 0.05) and that vigorous bacterial metabolism occurred in rice wine koji samples.

The Depth-Depended Fungal Diversity and Non-depth-Depended Aroma Profiles of Pit Mud for Strong-Flavor Baijiu

Microorganisms in pit mud are the essential factor determining the style of strong flavor Baijiu. The spatial distribution characteristics of fungal communities and aroma in the pit mud for strong flavor Baijiu from Xinjiang, China, were investigated using Illumina MiSeq high-throughput sequencing and electronic nose technology. A total of 138 fungal genera affiliated with 10 fungal phyla were identified from 27 pit mud samples; of these, Saccharomycopsis, Aspergillus, and Apiotrichum were the core fungal communities, and Aspergillus and Apiotrichum were the hubs that maintain the structural stability of fungal communities in pit mud. The fungal richness and diversity, as well as aroma of pit mud, showed no significant spatial heterogeneity, but divergences in pit mud at different depths were mainly in pH, total acid, and high abundance fungi. Moisture, NH4 +, and lactate were the main physicochemical factors involved in the maintenance of fungal stability and quality in pit mud, whereas pH had only a weak effect on fungi in pit mud. In addition, the fungal communities of pit mud were not significantly associated with the aroma. The results of this study provide a foundation for exploring the functional microorganisms and dissecting the brewing mechanism of strong flavor Baijiu in Xinjiang, and also contributes to the improvement of pit mud quality by bioaugmentation and controlling environmental physicochemical factors.

Diversity of microbiota, microbial functions, and flavor in different types of low-temperature Daqu

Light-flavor Baijiu is made from grain materials using a combination of three types of low-temperature Daqu (Hongxin, Houhuo, and Qingcha). This study comprehensively examined the microbial structure, microbial functions, and flavor characteristics of the three types of low-temperature Daqu using high-throughput sequencing and electronic senses, and it further clarified the relationship between the microbiota and flavor in low-temperature Daqu. The results showed that Hongxin had the highest bacterial richness and diversity, while Houhuo had the lowest. Both fungal richness and diversity were significantly higher in Qingcha than in Hongxin and Houhuo. The differences in peak temperature during Daqu-making led to significant differences in the structure of microbial communities, microbial functions, and flavor quality in the three types of low-temperature Daqu, and could be leveraged for screening and enriching functional microorganisms for Baijiu-making. Co-exclusion patterns between lactic acid bacteria and Bacillus in low-temperature Daqu resulted in a negative correlation between amino acid transport metabolism and carbohydrate transport metabolism. The different types of low-temperature Daqu had distinct flavor profiles, and the differences in the taste profiles were more significant. Dominated by Thermoactinomyces and Lactobacillus, and together with Saccharopolyspora, Bacillus, Streptomyces, Saccharomycopsis, and Thermoascus, they formed the core microbiota that influencing the flavor of low-temperature Daqu. The bacteria mainly influenced the taste of low-temperature Daqu, whereas the fungi mainly influenced the aroma. Each type of low-temperature Daqu contributed to the flavor of light-flavor Baijiu: Hongxin could elevate the levels of aromatic compounds, Houhuo could regulate the bitterness and sourness, and Qingcha could inhibit the generation of sulfur organic compounds. The results of the present study enrich and refine our knowledge of low-temperature Daqu, promoting the further evolution of traditional brewing methods.

The Fungal Communities and Flavor Profiles in Different Types of High-Temperature Daqu as Revealed by High-Throughput Sequencing and Electronic Senses

Polymicrobial co-fermentation is among the distinct character of high-temperature Daqu. However, fungal communities in the three types of high-temperature Daqu, namely, white high-temperature Daqu, black high-temperature Daqu, and yellow high-temperature Daqu, are yet to be characterized. In this study, the fungal diversity, taste, and aroma profiles in the three types of high-temperature Daqu were investigated by Illumina MiSeq high-throughput sequencing, electronic tongue, and electronic nose, respectively. Ascomycota and Basidiomycota were detected as the absolute dominant fungal phylum in all types of high-temperature Daqu samples, whereas Thermomyces, Thermoascus, Aspergillus, Rasamsonia, Byssochlamys, and Trichomonascus were identified as the dominant fungal genera. The fungal communities of the three types of high-temperature Daqu differed significantly (p < 0.05), and Thermomyces, Thermoascus, and Monascus could serve as the biomarkers in white high-temperature Daqu, black high-temperature Daqu, and yellow high-temperature Daqu, respectively. The three types of high-temperature Daqu had an extremely significant difference (p < 0.01) in flavor: white high-temperature Daqu was characterized by sourness, bitterness, astringency, richness, methane, alcohols, ketones, nitrogen oxides, and sulfur organic compounds; black high-temperature Daqu was characterized by aftertaste-A, aftertaste-B, methane-aliph, hydrogen, and aromatic compounds; and yellow high-temperature Daqu was characterized by saltiness, umami, methane, alcohols, ketones, nitrogen oxides, and sulfur organic compounds. The fungal communities in the three types of high-temperature Daqu were significantly correlated with taste but not with aroma, and the aroma of high-temperature Daqu was mainly influenced by the dominant fungal genera including Trichomonascus, Aspergillus, Thermoascus, and Thermomyces. The result of the present study enriched and refined our knowledge of high-temperature Daqu, which had positive implications for the development of traditional brewing technique.