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BACKGROUND: It has been well accepted that lactic acid bacteria (LAB) are the main bacterial genera present during the brewing of Chinese rice wine (CRW). LAB plays a decisive role in the flavor quality of CRW; however, its application in CRW has previously been overlooked. Therefore, effects of different LAB as co‐fermenter on the flavor characteristics of CRW were investigated. RESULTS: Co‐fermentation of LAB increased the utilization rate of reducing sugar, concentration of lactic acid, amino acid nitrogen and total acidity, as well as the content of volatile flavor compounds. Different LAB doses had little effect on the flavor profiles of CRW, but the species of LAB greatly affected the flavor characteristic. The flavor of CRW co‐fermented with Lactococcus lactis was characterized by long‐chain fatty acid ethyl esters, while co‐fermentation with Weissella confusa highlighted the ethyl esters of low molecular weight and short carbon chains in the resultant CRW. Alcohol compounds were dominant in the CRW co‐fermented using Pediococcus pentosaceus. CONCLUSION: The co‐fermentation of LAB increased the number of volatile flavor compounds, especially esters. LAB exhibited great potential in the application of CRW industry to enrich the flavor characteristics and enhance the flavor diversity of the final product. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND: Streptococcus thermophilus is a major starter used in the dairy industry and it could improve the flavor of fermented products. It is necessary to improve biomass of S. thermophilus for its application and industrialization. The utilization of carbon sources directly affects the biomass of S. thermophilus. Therefore, the carbohydrate metabolism of S. thermophilus should be investigated. RESULTS: In the present study, metabolic parameters and gene expression of S. thermophilus S‐3 with different carbon sources were investigated. The physicochemical results showed that S. thermophilus S‐3 had high lactose utilization. Transcriptome analysis found that approximately 104 genes were annotated onto 15 carbohydrate metabolic pathways, of which 15 unigenes were involved in the phosphotransferase system and 75 were involved in the ATP‐binding cassette transporter system. In addition, 171 differentially expressed genes related to carbohydrate metabolism were identified. Expression of the galactose metabolism genes lacSZ and galKTEM increased significantly from the lag phase to the mid‐exponential growth phase as a result of the global regulator protein, catabolite control protein A (CcpA). The high expression of galK in the mid‐ to late‐ phases indicated that the metabolite galactose is re‐transported for intracellular utilization. CcpA regulation may also induce high expressions of glycolytic pathway regulated‐genes related to lactose utilization, including ldh, fba, eno, pfkA, bglA, pgi, pgm and pyk, producing optimal glycolytic flux and S. thermophilus S‐3 growth. CONCLUSION: The present study provides new insights into the carbon metabolism regulation and provide theoretical support for high‐density fermentation of S. thermophilus S‐3. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Hong Qu Huangjiu (HQW) is distinguished by its inclusion of Monascus pigments, meaning that photosensitivity strongly affects the sensory quality of the wine. In this study, the effects of Flos sophorae immaturus (FSI) on the stability of Monascus pigments, the flavor profiles, and the sensory characteristics of HQW were investigated. After sterilization, the addition of FSI increased the preservation rate of Monascus pigments in HQW by up to 93.20%, which could be accounted for by the synergy of rutin and quercetin in FSI. The total content of the volatile flavor compounds in HQW increased significantly as the added amounts of FSI were increased, especially 3-methyl-1-butanol, 2-methyl-1-propanol, and short-chain fatty acid ethyl esters (SCFAEE). Sensory evaluation and partial least-squares regression revealed that the concentration of FSI significantly affected the aroma characteristics of HQW but had little effect on the mouthfeel. The addition of 0.9 mg/mL FSI yielded a satisfactory HQW with high scores in terms of mouthfeel and aroma. The strong correlation between fruit-aroma, full-body, and SCFAEE suggests that FSI might alter the aroma of HQW by enhancing the synthesis of SCFAEE. Summarily, treatment with FSI represents a new strategy for improving the stability of photosensitive pigments and thus adjusting the aroma of HQW or similar beverages. [ABSTRACT FROM AUTHOR]

[Display omitted] • L. salivarius AR809 could be used as adjunct culture to accelerate cheese ripening. • L. salivarius AR809 promoted the synthesis of methyl ketones for cheese maturation. • Monascus strengthened fatty acids metabolism and lysine degradation in the cheese. • AR809 and Monascus co-fermentation promote the metabolisms of amino acids and lipid. Adjunct cultures strongly determined the distinguishing sensorial and nutritional characteristics of cheeses. Metabolites, flavor profiles and ripening characteristics of Monascus -ripened cheese enhanced by the co-fermentation of Ligilactobacillus salivarius AR809 were investigated. The AR809 significantly increased the contents of soluble nitrogen, small peptides (<1200 Da), free amino acids, and casein degradation degree in the resulting cheese. Furthermore, AR809 significantly promoted the formation of methyl ketones during cheese maturation. Based on untargeted metabolomics analysis, metabolites related to fatty acids metabolism and lysine degradation were highly enriched in Monascus -rich region of cheese. AR809 was primarily engaged in amino acid metabolism, promoting the synthesis of amino acids and dipeptide. L. salivarius and Monascus co-fermentation produced more beneficial bioactive metabolites involved in amino acids and lipid metabolisms than Monascus used alone in cheese ripening. Therefore, as adjunct culture, L. salivarius AR809 exhibited tremendous potential in improving nutrition and flavor quality during cheese ripening. [ABSTRACT FROM AUTHOR]

Huangjiu (Chinese rice wine) has been consumed for centuries in Asian countries and is known for its unique flavor and subtle taste. The flavor compounds of Huangjiu are derived from a wide range of sources, such as raw materials, microbial metabolic activities during fermentation, and chemical reactions that occur during aging. Of these sources, microorganisms have the greatest effect on the flavor quality of Huangjiu. To enrich the microbial diversity, Huangjiu is generally fermented under an open environment, as this increases the complexity of its microbial community and flavor compounds. Thus, understanding the formation of flavor compounds in Huangjiu will be beneficial for producing a superior flavored product. In this paper, a critical review of aspects that may affect the formation of Huangjiu flavor compounds is presented. The selection of appropriate raw materials and the improvement of fermentation technologies to promote the flavor quality of Huangjiu are discussed. In addition, the effects of microbial community composition, metabolic function of predominant microorganisms, and dynamics of microbial community on the flavor quality of Huangjiu are examined. This review thus provides a theoretical basis for manipulating the fermentation process by using selected microorganisms to improve the overall flavor quality of Huangjiu. [ABSTRACT FROM AUTHOR]

The volatile compounds of Chinese rice wine fermented by Saccharomyces cerevisiae FC 15 and S. cerevisiae BR 30 and their combination (MIX) were investigated. The results showed that the wines fermented with different starters differed mainly in the numbers of alcohols and esters. Furthermore, the amounts of volatile compounds among three starters were also obviously different. After clarification, the loss of esters was greater than that of alcohols and aldehydes, whereas after sterilization, the loss of aldehydes was the greatest. PCA showed diethyl succinate to be the key flavor component. Moreover, short-chain fatty acid ethyl esters were main flavor substances during fermentation, whereas long-chain fatty acid ethyl esters were typical compounds after clarification and sterilization. Analysis of the ratio of higher alcohols to esters showed that BR 30 wine presented a stronger ester aroma than MIX wine, whereas FC 15 wine exhibited an outstanding alcohol flavor. Sensory evaluation indicated that FC 15 wine was intense in alcohol-aroma, whereas BR 30 wine exhibited high levels of cereal-aroma. Furthermore, both MIX and BR 30 wine were highly assessed in continuation and full body mouth-feel. It means that flavor characteristic of Chinese rice wine could be adjust by combination of yeast starters. [ABSTRACT FROM AUTHOR]

The influence of raw wheat Qu (RWQ) on the flavor quality of Huangjiu was investigated in this study. When used as a single saccharification starter, RWQ showed poor fermentation performance during Huangjiu brewing. However, as a co-fermentation starter with cooked wheat Qu (CWQ), RWQ considerably enhanced flavor quality of the resultant Huangjiu by promoting the accumulation of fatty acid ethyl esters (FAEEs) with odor activity values exceeding 1. Based on dynamic changes in bacterial diversity during Huangjiu brewing, a three-stage fermentation mode was identified for the first time. During stage III (5–15 d), the relative proportions of predominant genera Weissella and Lactococcus , which were strongly associated with the synthesis of FAEEs, were significantly adjusted by the co-fermentation of RWQ with CWQ. Moreover, co-fermentation of RWQ with CWQ reduced the bacterial diversity of Huangjiu samples, and this was strongly related to the total acidity (R 2 = 0.867) and ethanol (R 2 = 0.802) content. Therefore, the proportions of predominant bacteria were changed by RWQ, which affected bacterial diversity and enhanced the flavor quality of Huangjiu. Controlling environmental factors during brewing is suggested as a feasible way to regulate the proportions of bacterial genera, thereby regulating the flavor characteristic in the resultant wine. [Display omitted] • Based on changes in bacterial diversity, a three-stage fermentation mode of Huangjiu was found. • Co-fermentation of raw wheat Qu (RWQ) with cooked wheat Qu enhanced flavor quality of Huangjiu. • RWQ promoted the accumulation of fatty acid ethyl esters with OAVs exceeding 1. • RWQ adjusted proportions of Weissella and Lactococcus during stage III (5–15 d). [ABSTRACT FROM AUTHOR]

Huangjiu (Chinese rice wine), flavor compounds, microbial community, raw material, yeast starter, fungi, fermentation technology Keywords: Huangjiu (Chinese rice wine); flavor compounds; microbial community; raw material; fermentation technology; yeast starter; fungi EN Huangjiu (Chinese rice wine) flavor compounds microbial community raw material fermentation technology yeast starter fungi N.PAG N.PAG 2 03/03/21 20210225 NES 210225 In the original article, there was a mistake in Figure 2 as published. [Extracted from the article]

Soaking is a crucial process in adjusting initial fermentation acidity and achieving desired flavor quality of rice wines. Effects of soaking time on physicochemical characteristic of rice, flavor profiles, microbial community and sensory characteristic of Huangjiu were investigated. Soaking caused significantly changes in amylopectin content, and rice with high amylopectin content was conducive to produce esters and aldehydes during Hungjiu brewing. High-throughput sequencing showed that bacteria types were more abundant than fungi during brewing, suggesting that bacterial community might be primarily responsible for Huangjiu flavor. Differential analysis revealed that Weissella and Enterobacter contributed greatly to the accumulation of alcohols, esters and aldehydes during Huangjiu brewing, while Clostridium , Acinetobacter , Cyanobacteria , Zymomonas and Exiguobacterium were responsible for the rancidity. Based on spearman's correlation analysis, Lactococcus , Weissella , Pediococcus, Lactobacillus and Staphylococcus were the key microbial genera responsible for the flavor characteristic of Huangjiu. While favorable soaking caused an increased intensity in alcohol-aroma, full body and continuation of resultant Huangjiu, insufficient soaking led to a higher intensity of bitter taste. Summarily, soaking acidity ranged from 2 to 3 g/L was beneficial for preventing rancidity and improving the production of flavor compounds in Huangjiu. • High amylopectin content of soaked rice facilitated production of ester and aldehyde. • Weissella and Enterobacter contributed greatly to the flavor profiles of Huangjiu. • Insufficient soaking led to a higher intensity of bitter taste in resultant Huangjiu. • Soaking acidity of 2–3 g/L was beneficial for improving flavor profiles of Huangjiu. [ABSTRACT FROM AUTHOR]

[Display omitted] • Low field-NMR was firstly used in the age discrimination of Huangjiu. • Flavor compounds with ordor activity value (OAV) higher than 1 dominated the aging aroma of Huangjiu. • Basic amino acids greatly contributed to the flavor formation of Huangjiu during aging. • Molecular association promoted the accumulation of flavor compounds with OAV > 1. Aging is an essential operation to perfect the flavor quality of Hungjiu. In this study, formation mechanism of flavor compounds responsible for the characteristic flavor of aged Huangjiu was investigated. The contents of umami and bitter free amino acids (FAA) increased with the storage period prolonged, while that of sweet FAA showed downward trend. Gas chromatograph-mass spectrometry and principal component analysis indicated that the volatile flavor compounds with OAV exceed 1, especially middle-chain fatty-acid-ethyl-esters and aromatic compounds, dominated the characteristic flavor of aged Huangjiu. Low field-NMR was firstly applied to characterize the molecular association between water and dissolved flavor compounds in aged Huangjiu. The results showed that basic amino acids contributed greatly to the flavor formation of aged Huangjiu via molecular association. In addition, the molecular association significantly promoted the accumulation of flavor compounds with OAV > 1, especially ethyl esters. [ABSTRACT FROM AUTHOR]