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Daqu, a crucial fermentation starter in the production of various Chinese fermented foods, plays a pivotal role in shaping complex enzyme profiles and diverse flavour precursors. This review aims to elucidate the microbial communities within Daqu, focusing on their functionalities in the context of flavour development. We delve into the detection methods of microorganisms and flavour substances in Daqu, employing advanced technologies including high-performance liquid chromatography, gas chromatography, pseudo-targeted metabolomics, and headspace solid-phase microextraction-gas chromatography-mass spectrometry. This review explores high throughput sequencing technologies, including pyrosequencing, clonal library sequencing, metaproteomic, and metagenomics, to gain a comprehensive understanding of the intricate microbial dynamics. Additionally, we discuss the metabolic pathways involved in flavour substance production within Daqu. By synthesizing information on Daqu types, microorganisms present, detection methodologies, and flavour substance metabolic pathways, this review contributes to a deeper comprehension of the intricate processes underpinning the Flavors of Chinese fermented foods. [Display omitted] • Crucial role of Daqu in enzyme profiles and flavor precursors in Chinese foods. • Microbial communities in Daqu and their role in flavor development. • High throughput sequencing: pyrosequencing, clonal library sequencing, metaproteomic, metagenomics. • Comprehensive synthesis of Daqu types, microorganisms, and metabolic pathways. [ABSTRACT FROM AUTHOR]

In this study, a novel fluorescent probe DZ was designed by derivatizing from naphthaldehyde and benzoyl hydrazine. The probe exhibited a low detection limit of 1.75×10−8 mol/L for Zn2+ in ethanol systems. Due to its typical aggregation‐induced emission phenomenon, DZ showed exceptional efficacy in detecting the alcoholic strength of Chinese Baijiu, allowing for accurate differentiation between beverages with various alcohol contents in water/ethanol mixtures. In addition, DZ had been successfully utilized for the detection of Zn2+ in both test paper and environmental water samples. [ABSTRACT FROM AUTHOR]

A novel fingerprinting platform for multiplex detection of flavor molecules in Baijiu was developed by using a surface-enhanced Raman scattering (SERS) nanosensor array in combination with machine learning. The SERS sensors were constructed by core–shell Fe3O4@Ag nanoparticles modified with molecules carrying end-groups of hydroxyl, pyridyl, methyl, and amino, respectively, which interacted with flavors and led to changes in the sensors' spectra. All the Raman spectra acquired from the nanosensor array contacting with the sample were concatenated into a single SERS super-spectrum, representing the flavor fingerprint which was recognized through machine learning. Principal component analysis, support vector machine, and partial least squares were utilized to build classification and quantitation models for predictive analyses. The SERS nanosensor array was successfully used for fingerprinting ten typical flavors in Baijiu including four esters, three alcohols, and three acids, with an accuracy of 100%, linear detection ranges over two orders of magnitude, and limits of detection ranging from 3.45 × 10−3 mg/L of phenylethyl acetate to 1.21 × 10−2 mg/L of ethyl hexanoate. It was also demonstrated that satisfactory accuracies (recoveries) ranging from 96.2 to 104% and relative standard deviations ranging from 0.65 to 2.78% were obtained for the simultaneous quantification of 3-methylbutyl acetate and phenylethyl acetate in eighteen Baijiu samples of three flavor types including sauce flavor, strong flavor, and light flavor. Compared with the existing detection techniques, this chemical fingerprinting platform is easy to use, highly sensitive, and can perform multiplex detection, which has great potential for practical applications. [ABSTRACT FROM AUTHOR]

BACKGROUND: In industrial production of suancai, baijiu is commonly used to inhibit the spoilage bacteria and enhance the flavor. However, the effects of baijiu on the microbial diversity and metabolic pathways of suancai are rarely reported in the literature. This study aimed to explore the microbial community, its predicted functional roles, and the metabolites formed during fermentation of Chinese Dongbei suancai fermented using a mixed starter with Chinese baijiu as supplementary material. RESULTS: Results showed that Lactobacillus, Enterobacter, and Leuconostoc were the major bacterial genera in the Dongbei suancai fermented by adding baijiu. Linear discriminant analysis effect size indicated that Leuconostoc was the major biomarker in the early stage of fermentation, whereas Lactococcus, Weissella, and Lactobacillus plantarum were biomarkers in the middle and later stages of fermentation. A total of 638 metabolites were detected in suancai fermented by adding baijiu. However, the principal component analysis showed that baijiu significantly affected the metabolites of suancai in the early and later stages of fermentation. Furthermore, 58, 22, and 26 significantly differential metabolites (P < 0.01) were found on day 0, day 2, and day 30 of fermentation respectively. Moreover, Lactobacillus, Lactococcus, and Enterobacter had positive correlations with amino acids, nucleotides, organic acids, alcohols, and esters. Functional analysis implied that carbohydrate, amino acid, energy, and nucleotide metabolism were the major determinants of the characteristics of suancai fermented with baijiu as supplementary material. CONCLUSION: Baijiu changed the metabolites of inoculated fermented Dongbei suancai. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Chinese baijiu, an ancient fermented alcoholic beverage, contains ethanol and a variety of compounds. One of the most popular types of Chinese baijiu is Jiang-flavor baijiu. To investigate the effects of Jiang-flavor baijiu on organ function and gut microbiota, we developed a moderate drinking mouse model and studied its effects on the liver, kidney biomarkers, memory function, and gut microbiota. The results showed that ethanol caused more hepatic steatosis, liver and kidney damage, and memory impairment than Jiang-flavour baijiu consumption. Furthermore, Jiang-flavor baijiu altered the gut microbiota by increasing the abundance of beneficial taxa such as Lactobacillus and Akkermansia , whereas ethanol increased the abundance of harmful bacteria such as Prevotella and Mucispirillum. Our findings provide preliminary evidence that moderate dose Jiang-flavor baijiu regulates gut microbiota and organ function and provide a theoretical foundation for future research on the positive health effects of particular varieties of Chinese baijiu. [Display omitted] [ABSTRACT FROM AUTHOR]

BACKGROUND: The saccharification function of daqu is usually characterized by two indicators: saccharification power and liquefaction power. Daqu provides diverse microbial saccharifying enzymes for hydrolyzing carbohydrate in Baijiu fermenting grain. Obviously, the composition of microbial communities and enzymatic genes in different types of daqu cultured at varied temperatures is different. However, these differences in saccharification function are not fully understood. RESULTS: The findings suggested that the saccharification power and liquefaction power of jiangxiangxing daqu were lower than those of nongxiangxing daqu throughout the production process. We employed metagenomics to find evidence that a mode of multiple saccharifying enzymes involving amylase, cellulase and hemicellulase originating from various microbes exists in daqu. Moreover, a totality of 541 related differential genes were obtained, some of which, annotated to genera of Aspergillus, Lactobacillus and Weissella, were significantly enriched (P < 0.05) in nongxiangxing daqu, while others, annotated to thermophilic genera of Virgibacillus, Bacillus, Kroppenstedtia and Saccharopolyspora, showed a higher relative abundance in jiangxiangxing daqu (P < 0.05). CONCLUSION: Various microbial communities of daqu showed diverse saccharification capacity during cultivation of different parameters. These findings are helpful in comprehending the saccharification functional genes of daqu. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

In traditional Chinese Baijiu (white wine) brewing factory, most processes were usually done manually. In order to promote industrial automation in liquor brewing industry and alleviate highly repetitive manual labor, an industrial robot operating system equipped with machine vision was designed to accomplish caldron feeding process during the distillation of Chinese Baijiu. Firstly, Modified D-H method was used to establish robot kinematics model. Shovel actuators and peripheral devices were designed to spread and transport grains during caldron feeding process. After that, an online detection system based on machine vision and master computer were designed to control key parameters of caldron feeding process, including grains height, caldron pressure, robot speed and waiting time, etc. Finally, multiple brewing experiments were carried out on crushed grains and spent grains. The experimental results showed that robot system maximum working space was 3.15 m, which could feed 3 caldrons at the same time. During Chinese Baijiu distillation, air pressure average error in caldron was 8.28 %. High proportion of first-class liquor and second-class liquor was obtained, which met engineering production requirements. [ABSTRACT FROM AUTHOR]

Acetaldehyde (AH) is defined as a carcinogen, the widely existence in alcoholic beverages has led its determination an essential aspect related to human health. Fluorine doped carbon dots (dF-CDs) is developed, which process light-activated oxidase-mimic property and high stability at acidic condition. Under the UV irradiation, dF-CDs generate reactive oxygen species (ROS) to oxidize o -phenylenediamine (OPD) into 2,3-diaminophenazine (DAP), showing absorption peak at 450 nm and strong emission at 577 nm, meanwhile, the produced DAP quenches the original emission of dF-CDs at 455 nm via an inner filter effect (IFE). However, the introduction of AH inhibits such processes efficiently, thereby establishing a colorimetry and ratiometric fluorescence method for AH determination. Of note, this dual-responsive method has been used for the accurate AH determination in Chinese Baijiu. Therefore, the developed method not only provide a dual-sensing platform to determine AH, but also extends the applications of CDs in food analysis. [Display omitted] • Fluorine-containing CDs (dF-CDs) with light-activated oxidase property is reported. • dF-CDs are more stable and highly resistant to acidity than OPD-CDs. • dF-CDs show colorimetric & ratiometric emission responses to aldehyde in Baijiu. • A portable UV lamp enables precise control of the reaction degree. • The method is universal for acetaldehyde determination in various aroma Baijiu. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive review on the effect and mechanism of sorghum (Sorghum bicolor) grain composition on the quality of Chinese baijiu. Sorghum has emerged as the fifth largest cereal crop worldwide due to its agricultural advantages, such as drought and barren tolerance. Moreover, it can be processed and utilized in various ways, thus playing a crucial role in ensuring food security. Chinese baijiu, which is mainly brewed from sorghum grain, has gained immense popularity among Chinese consumers owing to its distinctive flavor. Previous studies have indicated that the quality of sorghum baijiu is significantly influenced by the quality of raw material, with key determinants including starch, protein, tannin, fat, and other components in sorghum grain. Understanding the mechanism of these constituents on affecting baijiu quality is of paramount importance in enhancing and developing flavors that cater to diverse consumer preferences. This paper provided a comprehensive summary on the parameters of sorghum grain quality, in association with baijiu quality, and also highlighted the potential areas for future research in the sorghum baijiu industry. • Research advances on Chinese sorghum liquor were comprehensively summarized. • Integrate and visualize the production flow of Chinese liquor's three major flavors. • Drawbacks of past students and perspectives for future research were discussed. • Hundreds of articles were referenced with 33 % of them were published in 2019–2023. [ABSTRACT FROM AUTHOR]

Molecular mechanisms underlying the aging of Chinese Baijiu remained elusive. This study proposed the self-assembly behavior of amphiphilic molecules dominated by hydrogen bonds in Chinese Baijiu for the first time. The self-assembly degree of amphiphilic clusters gradually intensifies with the prolonged storage time of Baijiu, comprehensively characterized at both micro and macro levels. The results indicated that the blue-shift of the Raman hydrogen bond vibrational peak (about 11 cm−1 and 7 cm−1, respectively), the increase in viscosity (5.71% and 2.22%, respectively), and the rise in dielectric constant (95.63% and 94.99%, respectively) during the 17-year cellaring process of Strong-flavor Baijiu and Jiang-flavor Baijiu were consistent with the evolutionary trends observed in molecular dynamics simulations. The essential driving factors of cluster structure alteration of amphiphilic aroma substances in Chinese Baijiu during cellaring were demonstrated from molecular level. This study provided a research approach to comprehending the aging mechanism of Chinese Baijiu from the micro level. [Display omitted] • The self-assembly behavior of amphiphilic molecules driving the formation of hydrogen bonds in Chinese Baijiu is proposed for the first time. • The self-assembly behavior of amphiphilic molecules in Baijiu was comprehensively characterized at both micro and macro levels. • The unidirectional gradient variation observed in the impedance spectrum of aged Baijiu recorded by EIS serve as a powerful tool for elucidating the detailed molecular mechanism of self-assembly during the aging process of Chinese Baijiu. [ABSTRACT FROM AUTHOR]

Changes in the content and morphology of residual starch in Zaopei during strong‐flavor Baijiu fermentation are investigated. The results show that the residual starch content increases through the Baijiu production and that the residual starch content of distiller's grains (DGS) is the highest (76.35%). The crystalline structure of starch changes from A‐type (raw grain starch) to B + V‐type (Zaopei, Hongzao, Mianzao, DGS). The upper Zaopei starch has the typical diffraction peaks of B + V‐type (7.4°, 12.8°, 14.9°, 19.7°, 19.6°, 26.6°) and retains the typical diffraction peaks of A‐type (17.0°, 22.2°). The intermediate and bottom Zaopei starch has the typical diffraction peaks of B + V‐type (7.4°, 12.8°, 16.9°, 19.7°, 20.7°, 26.6°) and loses the typical diffraction peaks of A‐type. With the progression of Baijiu production, the gelatinization temperature and enthalpy of starch increase, while the water‐holding capacity, freeze‐thaw stability, solubility, and swelling power decrease. The above results show that the starch complex is the primary form of residual starch in strong‐flavor Baijiu. [ABSTRACT FROM AUTHOR]

Summary: Daqu provides hydrolytic enzymes that saccharifying the macromolecular carbohydrate in fermenting grains. The process of saccharification is the premise of Baijiu production. But little is known about the protein composition associated with the activity of saccharifying enzymes in daqu. This study investigated related proteins between nongxiangxing daqu and jiangxiangxing daqu by metaproteomics. We present that the amylase system (α‐amylase, glucoamylase and α‐glucosidase) and cellulase system (cellobiohydrolases, endoglucanase and β‐glucosidase) are regarded as the main saccharifying enzymes. Combined with protein‐based taxonomic annotation, the key proteins involving in amylase system were mainly from Kroppenstedtia, Lichtheimia, Byssochlamys and Thermomyces, while Thermoascu contributed the most to cellulase system. Moreover, it was found that the up‐regulated amylase proteins at thermophilic fermentation period in jiangxiangxing daqu in comparison with nongxiangxing daqu were affiliated to Aspergillus, Rhizomucor, Byssochlamys and Thermomyces, along with Thermoascu contributing to cellulase system. These findings will provide clues for improving saccharification efficiency in Baijiu production. [ABSTRACT FROM AUTHOR]

Chinese Baijiu (Liquor) is a popular alcoholic beverage, and the ethanol content in Baijiu is closely related to its quality; therefore, it is of great significance to explore a facile, sensitive, and rapid method to detect ethanol content in Baijiu. Hydrophobic carbon quantum dots (H-CQDs) with bright red fluorescence (24.14 %) were fabricated by hydrothermal method using o -phenylenediamine, p -aminobenzoic acid, manganese chloride, and hydrochloric acid as reaction precursors. After the introduction of ultrapure water into the ethanol solution dissolved with H-CQDs, the aggregated H-CQDs resulted in significant changes in fluorescence intensity and absorbance. On this basis, a sensor for detecting ethanol by optical dual-mode and smartphone imaging was constructed. More importantly, the sensor can be used for detecting ethanol content in Chinese Baijiu with satisfactory results. This sensing platform has great potential for quality identification in Chinese Baijiu, broadening the application scope of CQDs in food safety detection. [Display omitted] • A hydrophobic carbon quantum dots (H-CQDs) co-doped with Mn, Cl, and N. • H-CQDs-based optical dual-mode and smartphone imaging for detecting ethanol content. • The sensor with high selectivity and excellent anti-interference capability. • H-CQDs was successfully applied for detecting ethanol content in Chinese Baijiu. [ABSTRACT FROM AUTHOR]

We have investigated the effect of light-to-moderate baijiu consumption on serum lipid metabolism and liver function in vivo. To this end, six groups of rats received increasing dosage of baijiu (0.5–5.0mL/kg) for 8 weeks and multiple markers of lipid metabolism and liver function were evaluated. Compared to that of the blank control, at the baijiu dosage of 3.0mL/kg, the levels of high-density lipoprotein cholesterol, reduced glutathione, glutathione peroxidase, superoxide dismutase, and total antioxidant capacity increased significantly (P<0.05), whereas malondialdehyde level decreased (P<0.05). In comparison to the pure ethanol groups, with baijiu groups at the same level of alcohol revealed that baijiu had noticeably positive impact in ameliorating the changes in the values of all parameters examined. In summary, regular consumption of light-to-moderate amount of baijiu may significantly enhance the metabolism of serum lipids and enhance liver function. [ABSTRACT FROM AUTHOR]

In this study, the novel polysaccharides named HSP-0 M and HSP-0.1 M were successfully purified from Huangshui (HS), and their structural properties and bioactivities were investigated. Structural analysis revealed that HSP-0 M had a molecular weight of 493.87 kDa and was composed of arabinose, galactose, glucose, xylose, and mannose in a molar ratio of 1.48:1.09:26.52:1.33:1.00. On the other hand, HSP-0.1 M was made up of fructose, arabinose, galactose, glucose, xylose, mannose, ribose, galacturonic acid and glucuronic acid in a ratio of 2.67:26.00:29.10:36.83:16.22:30.53:1.00:1.43:3.64 with a molecular weight of 157.6 kDa. Methylated and 2D NMR analyses indicated that T-Glc p -(1 → 4)-Glc p -(1 → 2)-Glc p -(1 → 3)-Glc p was the primary chain of HSP-0 M, and the backbone of HSP-0.1 M was made up of →3)-Gal p -(1 → 6)-Man p -(1 → 3)-Glc p -(1 → 6)-Glc p -(1 → 2)-Man p -(1 → 6)-Glc p -(1 → 3)-Gal p. Morphological research showed that both polysaccharides were homogeneous as well as exhibit a web-like structure and an irregular lamellar structure. Furthermore, HSP-0 M demonstrated the capacity to safeguard Lactococcus lactis from damage caused by low temperatures and freeze-drying, while HSP-0.1 M exhibited noteworthy antioxidant activity. These results established a theoretical foundation for the applications of HSPs in food products, cosmetics, and medicines. • Two novel polysaccharides (HSP-0 M and HSP-0.1 M) from Huangshui were purified. • The structures and morphologies of two HSPs were comprehensively elaborated. • Bioactivities with antioxidant, cryoprotective and lyophilized protective activities of two HSPs were investigated. • HSP-0.1 M exhibited significant antioxidant activity. • HSP-0 M presented cryoprotective and freeze-drying protective effects on L. lactis MG1363. [ABSTRACT FROM AUTHOR]

Huangshui (HS) has attracted considerable attention for the utilization of aroma compounds and microorganisms containing presently. However, little work has been done on biological polysaccharides in HS. In this study, a novel water-eluted HS polysaccharide, HSP-W, was identified as an α -D-glucan with a Mw of 166.00 kDa. It was consisted of a 1,4 linked α -D-Glc p backbone with the substitution at O-6 with 1,6-linked α -D-Glc p residue and non-reducing terminal of β -Glc-1→ through monosaccharide composition, IR, methylation, and NMR analyses. SEM, AFM, and particle size distribution measurements showed that HSP-W had relatively clustered spherical shape with different sizes from nanoscale to micrometer. Additionally, HSP-W significantly induced NO and ROS production as well as the release of IL-1 β , IFN- γ , TNF- α , and IL-6, and upregulated pinocytic and phagocytic capacities of THP-1 cells. Meanwhile, HSP-W treatment markedly enhanced mRNA and protein expressions of these cytokines. HS probably has potential application as an immunostimulatory agent. Unlabelled Image • A novel water-eluted Huangshui polysaccharide (HSP-W) was identified as an α -D-glucan. • The structure of HSP-W was identified by FT-IR, methylation analysis, and NMR. • SEM and AFM showed that HSP-W had clustered spherical shape with different sizes. • HSP-W markedly induced mRNA and protein expressions of cytokines. [ABSTRACT FROM AUTHOR]

d-Limonene, a cyclic monoterpene, possesses citrus-like olfactory property and multi-physiological functions. In this study, the d-limonene synthase (tLS) from Citrus limon was codon-optimized and heterologously expressed in Saccharomyces cerevisiae. The metabolic flux of canonical pathway based on overexpressing endogenous geranyl diphosphate synthase gene (ERG20) and its variant ERG20F96W−N127W was strengthened for improvement d-limonene production in Chinese Baijiu. To further elevate production, we established an orthogonal pathway by introducing neryl diphosphate synthase 1 (tNDPS1) from Solanum lycopersicum. The results showed that expressing ERG20 and ERG20F96W−N127W could enhance d-limonene synthesis, while expressing heterologous NPP synthase gene significantly increase d-limonene formation. Furthermore, we constructed a tLS–tNDPS1 fusion protein, and the best strain yielded 9.8 mg/L d-limonene after optimizing the amino acid linker and fusion order, a 40% improvement over the free enzymes during Chinese Baijiu fermentation. Finally, under the optimized fermentation conditions, a maximum d-limonene content of 23.7 mg/L in strain AY12α-L9 was achieved, which was the highest reported production in Chinese Baijiu. In addition, we also investigated that the effect of d-limonene concentration on yeast growth and fermentation. This study provided a meaningful insight into the platform for other valuable monoterpenes biosynthesis in Chinese Baijiu fermentation. [ABSTRACT FROM AUTHOR]

Baijiu – Chinese white spirits – contain a plethora of volatile compounds of which only some have been identified. This study reports two pre‐treatments, direct injection and headspace solid phase microextraction (HS‐SPME), coupled with gas chromatography mass spectrometry to analyse the volatile compounds of liquor distilled from grains fermented in 100‐, 200‐ and 300 year‐old cellars. Three samples from each cellar were analysed and 71 compounds were detected using direct injection with 75 compounds detected using HS‐SPME. The compounds included esters, alcohols, carboxylic acids, aldehydes and ketones and other compounds. Although both methods detected a similar number of compounds, the types of compounds detected differed. The collection times of the samples were divided into four stages according to their composition. This study provides an analytical foundation for further determining components in baijiu. © 2019 The Institute of Brewing & Distilling [ABSTRACT FROM AUTHOR]

Appearance features serve as pivotal metrics for regulating the Daqu fermentation process and assessing its quality. Nevertheless, uncertainties persist regarding the variances in microbial community structure and potential functions during Daqu fermentation with distinct appearance features. Employing amplicon sequencing technology, this study scrutinized low-temperature Daqu sample groups (Y and C) exhibiting discernible differences in appearance features. The results elucidated that microbial α-diversity within the Y group aligned with fluctuations in temperature and moisture during LT-Daqu fermentation, a contrast observed in the C group. Concomitant β-diversity and dominant microbial succession analyses revealed disparate microbial community structures between these groups. Co-occurrence network analysis indicated heightened microbial interconnectivity within the Y group. Compared with the C group, the Y group showcased a greater abundance of relevant genes in the Glycolysis/Gluconeogenesis pathway. T test analysis delineated markedly distinct microorganisms at various fermentation stages, with Streptomyces , Staphylococcus , and Saccharomycopsis enriched in the Y group, and Lactobacillus , Wickerhamomyces , and Aspergillus in the C group. This comprehensive investigations revealed the difference of microbial community structure and function of LT-Daqu with different appearance features, providing insights for refining fermentation procedures and quality evaluation. Moreover, it contributes to an enhanced understanding of fermentation mechanisms in analogous domains. [Display omitted] • The microbial community exhibited significant differences between two types of LT-Daqu with distinct appearance features. • Two types of Daqu with different appearance features had the same dominant microorganisms. • Daqu with different appearance features can provide distinct functionality and flavor contributions. [ABSTRACT FROM AUTHOR]

[Display omitted] • With a large Stokes shift and a low detection limit for the detection of aluminum ion. • A high sensitivity for detecting water content in organic solvents. • Quantitative detection of alcoholic strength in Chinese Baijiu with an excellent recovery. • Simple test strips were used to distinguish various Chinese Baijius with different alcoholic strength. Developing highly sensitive fluorescent probe for Al3+ and H 2 O detection is highly desirable, due to aluminum toxicity poses a significant threat to public health. On the other hand, the determination of water content holds immense significance in a wide range of fields such as food processing, pharmaceutical manufacturing. In this paper, a novel acylhydrazone-based fluorescent probe P was successfully synthesized and characterized for the sequential detection of Al3+ and water in alcohols. The probe P exhibited a remarkable "turn-on" response towards Al3+ by emitting yellow fluorescence at 567 nm, with high selectivity and large Stokes shift (147 nm). Meanwhile, the in situ formed P -Al3+ complex demonstrated significant solvatofluorochromic characteristic, which could be utilized as a second probe for detecting water via fluorescence quenching with low detection limit in alcohols (0.008%, methanol; 0.013%, ethanol; 0.013%, isopropanol; 0.037%, n-butanol; vol.%) and acetonitrile (0.072%, vol.%). Moreover, the P -Al3+ complex was able to detect the alcoholic strength of Chinese Baijiu without the interference of other alcohols, providing an excellent recovery rate (100.0–107.0%). Different Chinese Baijius, with various alcoholic strength, could be distinguished by simple test strips. Furthermore, the P -Al3+ complex could also analyze the water content in organic solvents. [ABSTRACT FROM AUTHOR]

• A red-emission PPD-CQDs was applied for ethanol determination in Chinese Baijiu. • The red-emission eliminated the optical interference originated from Baijiu body. • PPD-CQDs responded to ethanol contents in E-Ws or Baijiu linearly, but differently. • The deviation between them was attributed to the lower pH of Baijiu than E-Ws. • A pH correction on Baijiu established a universal method for ethanol determination. The quality control of Baijiu is necessary including ethanol content. In this work, red-emitted carbon quantum dots based on p -phenylenediamine (PPD-CQDs) were fabricated for accurate determination of ethanol in Baijiu. The good linear response of PPD-CQDs to ethanol–water solution (E-Ws; 20–80 vol%) offered the potential for ethanol determination in practice. However, further application of this procedure to Baijiu resulted in a certain deviation. After excluding interference from most of the ingredients involved, a simple pH correction on Baijiu made application of the process practicable. The red-emission of PPD-CQDs supported analysis of Baijiu with different flavors and ethanol monitoring. Therefore, a quick-response fluorescence method was established for Baijiu ethanol determination; this method can be applied to the many varieties of Chinese Baijiu available and also has potential for use in other alcoholic beverages. [ABSTRACT FROM AUTHOR]

A comprehensive understanding of the molecular composition of Chinese baijiu is of great value for understanding the flavor and improving the quality. Liquid chromatography-mass spectrometry (LC-MS) is a good tool for the analysis of Chinese baijiu. However, the lack of a related database makes it difficult to annotate corresponding LC-MS data. Therefore, a Chinese baijiu compound database (CBDB) containing 5709 compounds was constructed based on literature and text mining, and further, a Chinese baijiu LC-MS database (LCMS-CBDB) was built by endowing each compound with retention time, exact mass, and MS2 information. In total, 468 compounds were identified in six Chinese baijiu samples by searching LCMS-CBDB. Further, 2 database enhancement strategies were proposed based on biological transformation and theoretical homologue expansion. As an example, four monoglycerides were successfully identified and validated using the extended CBDB, and three of them were reported in baijiu for the first time. [Display omitted] • Chinese baijiu compound database (CBDB) containing 5709 compounds was constructed. • LC-MS database of CBDB (LCMS-CBDB) was built with t R , MS1, and MS2. • LCMS-CBDB can be used for simple and rapid identification of components in baijiu. • Extended identification method can be used to discover new compounds in baijiu. [ABSTRACT FROM AUTHOR]

Acetate esters and higher alcohols significantly determine the flavor profiles of Chinese Baijiu (Chinese liquor). The aminotransferase encoded by BAT2 and alcohol acetyltransferases encoded by ATF1, ATF2, and Lg-ATF1 are involved in the production of branched-chain alcohols and synthesis of acetate esters, respectively. In this study, the effects of ATF1, ATF2, and Lg-ATF1 overexpressions with BAT2 deletion were explored in Chinese Baijiu yeast. The differences among these effects were also investigated. Results showed that the productions of acetate esters by mutant overexpressing ATF1 with BAT2 deletion and that overexpressing ATF2 with BAT2 deletion were 1353.45 and 73.40 mg/L, respectively, which were 43.16- and 2.34-fold higher than that by the original strain. Compared with mutant overexpressing ATF2 with BAT2 deletion, mutant overexpressing ATF1 with BAT2 deletion exhibited 48.17% decreased higher alcohol productivity. The production of higher alcohols in mutant overexpressing ATF2 with BAT2 deletion was similar to that in the BAT2 deletion mutant. Furthermore, no significant difference was observed between the BAT2 deletion mutant and the mutant overexpressing Lg-ATF1 with BAT2 deletion in terms of acetate ester and higher alcohol production. The mutants that have varying capacities for acetate ester and higher alcohol production can be potentially developed and applied. [ABSTRACT FROM AUTHOR]

One of famous Chinese Baijiu, Gujinggong (GJG) that is produced in Anhui province, belongs to the famous Luzhou-aroma type of Baijiu in regards of its unique flavor characteristics. However, its key aroma-impact volatiles have not been clearly characterized. In this study, a total of 60 aroma compounds of GJG were identified by GC-O and GC–MS, and 35 of them were further recognized as important aroma compounds owing to their OAVs ≥ 1 and sensory evaluation. As a result, its aroma profile was successfully simulated by reconstitution of those 35 and other 11 aroma compounds based on their measured concentrations in the GJG. Moreover, omission test was applied to investigate the effects of the important aroma compounds on the whole aroma profile of GJG. In this context, 9 aroma compounds were confirmed as the key aroma compounds of GJG. [ABSTRACT FROM AUTHOR]

Higher alcohols significantly influence the quality and flavor profiles of Chinese Baijiu. ILV1-encoded threonine deaminase, LEU1-encoded α-isopropylmalate dehydrogenase, and LEU2-encoded β-isopropylmalate dehydrogenase are involved in the production of higher alcohols. In this work, ILV1, LEU1, and LEU2 deletions in α-type haploid, a-type haploid, and diploid Saccharomyces cerevisiae strains and ILV1, LEU1, and LEU2 single-allele deletions in diploid strains were constructed to examine the effects of these alterations on the metabolism of higher alcohols. Results showed that different genetic engineering strategies influence carbon flux and higher alcohol metabolism in different manners. Compared with the parental diploid strain, the ILV1 double-allele-deletion diploid mutant produced lower concentrations of n-propanol, active amyl alcohol, and 2-phenylethanol by 30.33, 35.58, and 11.71%, respectively. Moreover, the production of isobutanol and isoamyl alcohol increased by 326.39 and 57.6%, respectively. The LEU1 double-allele-deletion diploid mutant exhibited 14.09% increased n-propanol, 33.74% decreased isoamyl alcohol, and 13.21% decreased 2-phenylethanol production, which were similar to those of the LEU2 mutant. Furthermore, the LEU1 and LEU2 double-allele-deletion diploid mutants exhibited 41.72 and 52.18% increased isobutanol production, respectively. The effects of ILV1, LEU1, and LEU2 deletions on the production of higher alcohols by α-type and a-type haploid strains were similar to those of double-allele deletion in diploid strains. Moreover, the isobutanol production of the ILV1 single-allele-deletion diploid strain increased by 27.76%. Variations in higher alcohol production by the mutants are due to the carbon flux changes in yeast metabolism. This study could provide a valuable reference for further research on higher alcohol metabolism and future optimization of yeast strains for alcoholic beverages. [ABSTRACT FROM AUTHOR]

Acetate esters and higher alcohols greatly influence the quality and flavor profiles of Chinese Baijiu (Chinese liquor). Various mutants have been constructed to investigate the interactions of ATF1 overexpression, IAH1 deletion, and BAT2 deletion on the production of acetate esters and higher alcohols. The results showed that the overexpression of ATF1 under the control of the PGK1 promoter with BAT2 and IAH1 double-gene deletion led to a higher production of acetate esters and a lower production of higher alcohols than the overexpression of ATF1 with IAH1 deletion or overexpression of ATF1 with BAT2 deletion. Moreover, deletion of IAH1 in ATF1 overexpression strains effectively increased the production of isobutyl acetate and isoamyl acetate by reducing the hydrolysis of acetate esters. The decline in the production of higher alcohol by the ATF1 overexpression strains with BAT2 deletion is due to the interaction of ATF1 overexpression and BAT2 deletion. Mutants with varying abilities of producing acetate esters and higher alcohols were developed by genetic engineering. These strains have great potential for industrial application. [ABSTRACT FROM AUTHOR]

Chinese Baijiu (Chinese spirit or Chinese liquor) is one of the six major distilled spirits in the world, and is renowned overseas. Chinese Baijiu has a long history of more than 1000 years when people first begin to brew liquor using distillation. So far, Chinese Baijius have formed 12 types according to their flavour characteristics. The strong flavour Chinese spirit is regarded as one of the typical representatives, and occupies a > 70% market share in China. The liquor brewing process is under an open environment, with grains as the fermentation substrates, as well as Daqu as the saccharifying ferment. The brewing process is complex and impacted by multiple factors. Among the factors, the microorganisms have important influences on the brewing process and product quality of liquors. In the past decades, a series of research achievements have been made with strong flavour Chinese spirits. However, reviews related to this field are relatively few. In this paper, we have reviewed strong flavour Chinese spirits including the introduction, brewing process, microorganism diversity of Daqus, fermented grains and pit muds, and the application of microbes. Copyright © 2017 The Institute of Brewing & Distilling [ABSTRACT FROM AUTHOR]

Chinese Baijiu is a traditional distilled spirit that is consumed abundantly in China and around the world. Aging would dramatically increase the flavor of Baijiu, and famous Baijiu usually needs the long storage time for aging. Therefore, artificial aging that could accelerate the flavor improvement is in high demand. In this study, an electric-field treatment device was developed for the electric-field aging of the liquor. We used three types of strong-flavor crude Baijiu from different manufacturers in Sichuan as samples for electric-field aging. The total acids and esters, volatile flavor components, and sensory evaluation of the Baijiu samples before and after treatment were determined. It was found that the total acids and total esters of the Baijiu samples decreased and increased, respectively, with aging. The composition of volatile components changed after the aging treatment, and the volatile flavor components associated with the changes in the quality of Baijiu were analyzed. Combined with the sensory evaluation results, it was concluded that the quality of the treated Baijiu was significantly improved via electric-field aging. The result showed that electric-field aging can be an effective way to improve the flavor of Baijiu. • We developed a small-scale electric field treatment equipment for artificial aging of Baijiu. • The effect of this electric field treatment apparatus on the quality of three strong-flavor crude Baijiu was investigated. • Provide a new direction for artificial aging of Chinese Baijiu. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel dual-channel fluorescence sensor array was first proposed. • The array was designed by o-phenylenediamine/3,4-diaminotoluene and pyrocatechol. • 10 flavor compounds could be quantified in this study. • 32 aroma types, brands and grades of Baijiu could be well discriminated. An effective method to discriminate Baijiu carries important applications for grade identification and quality control in the Baijiu industry. Herein, we report on a novel and straightforward dual-channel fluorescence sensor array for flavor compounds (FCs) and Chinese Baijiu discrimination. Unit 1 (U1) is the reaction between o-phenylenediamine (OPD) and pyrocatechol (ODHB), and unit 2 (U2) is the reaction between 3,4-diaminotoluene (3,4-DAT) and ODHB. The fluorescent products were changed via FCs in Baijiu relying on the influence of protonation of the amino group on OPD/3,4-DAT and chemical reactions. The array successfully achieves qualitative and quantitative identification of FCs with low detection limits and wide linear ranges. In addition, qualitative identification of 0.7 mmol/L FCs in Baijiu is achieved. Finally, this is applied to discriminate 32 Baijius varieties with different aromas, brands, and grades. The fluorescence sensor array is reliable and straightforward for FCs identification and Baijius discrimination, which is of great significance for authenticity identification in the Baijiu industry. [ABSTRACT FROM AUTHOR]

As one of the oldest distillates in the world, flavor compounds of Chinese Baijiu (Chinese liquor) were extremely complex. Propyl lactate was firstly detected by direct injection and gas chromatography-mass spectrometry (GC-MS) in 72 Chinese Baijius. The objectives were to detect the contents of propyl lactate and evaluate its contribution to the aroma of Chinese Baijiu based on odor activity values (OAVs). The levels of propyl lactate in these distillates were determined by internal standard method and selective ion monitoring (SIM), which ranged from 0.050 to 1.900 mg·L-1 under investigation. Its detection threshold was determined by Three-Alternative Forced-Choice (3-AFC) and curve fitting (CF), which was 0.740 mg·L-1 in 38% ethanol solution. The contribution of propyl lactate on the aroma of these distillate drinks was evaluated by their odor activity values (OAVs), which varied from 0.066 to 4.440. The OAVs of propyl lactate were found to exceed 1 in 13 Chinese Baijius, including 50° Jingzhi Guniang 5 years (4.440), 52° Jingzhi Guniang 10 years (3.024), Jingyanggang (2.568), Xianghe Ronghe Shaofang (2.313), and 1956 Laolang (1.431), which indicated that propyl lactate was one of odor-active components in these Chinese Baijius. [ABSTRACT FROM AUTHOR]

[Display omitted] • The microbial community of SFB workshops microecology were identified. • Enrich the microbial profiles information by high-throughput sequencing. • The microbial composition in the workshop environment has succession in time series. • The bacterial community in brewing environment tends to be stable as the use time increases. The strong-flavor Baijiu (SFB) brewing workshop is a complex ecosystem with diverse microbiomes. As a potential source of microbiomes in fermentation, microbiota in the environmental microecology may affect the quality and flavor of SFB. Here, we report the collection of environmental microecological samples from three SFB workshops with different usage times (named 70a, 30a, and new, respectively). We used 16S rRNA and internal transcribed spacer (ITS) gene amplicon full-length sequencing to explore the microbial community structure in SFB. The SourceTracker tool was used to investigate links among fermentation samples, raw materials, and the environment and decipher the construction process in the workshop indoor environment. Lactobacillus acetotolerans was the most important bacterial genus in Zaopei after fermentation, whereas other types of samples exhibited different prokaryotic community structures. The composition of the fungal community was similar, with Saccharomycopsis fibuligera , Debaryomyces hansenii , Lichtheimia ramosa , Lichtheimia corymbifera , and Pichia kudriavzevii being the most abundant, and were detected in most samples. Further comparison of the microbiota in the workshop environment showed that the diversity of the microbiota in the indoor environment decreased, showing different clustering patterns under the influence of location. With increasing usage time, the contribution of deterministic processes to the assembly of the prokaryotic community increases, and the community structure tends to stabilize, exhibiting its own characteristics. SFB-fermenting resident functional fungi were the major components of the fungal community, and SourceTracker analysis also highlighted the contributions of Zaopei, Daqu, and tool surfaces as fungal sources. This study is the first to comprehensively monitor the microbial profile of the SFB production environment. This research can be extended to involve more complex spontaneous fermentation environment microbiota and has important implications for the control of spontaneous fermentation. [ABSTRACT FROM AUTHOR]

Since Baijiu, a traditionally distilled Chinese spirit, is widely consumed, the health risks of the ethyl carbamate (EC) content are of significant concern. To assess the EC content and evaluate dietary exposure risk to Chinese Baijiu, 2039 Baijiu samples, including 715 Strong-flavor Baijiu (SFB), 702 Jiang-flavor Baijiu (JFB), and 622 Light-flavor Baijiu (LFB), were collected from 16 provinces. The mean EC concentration was 62.26 μg/L, ranging from n.d. to 382.33 μg/L. Moreover, SFB exhibited higher EC content (113.94 μg/L) than JFB (58.10 μg/L) and LFB (12.02 μg/L). The EC content varied between different geographic areas and was especially evident between East China and other regions. Based on Baijiu consumption data, the daily exposure to EC was calculated as 40 ng/kg bw/day for regular consumers, while SFB drinkers displayed a higher intake (73.2 ng/kg bw/day). The margin of exposure (MOE) indicated that the EC in SFB and JFB posed various health risks, necessitating the development of stricter supervision while reducing consumption to regulate the EC level in SFB and JFB. In addition, this study identified safe drinking limits for consumers, recommending 0.46 L/month for SFB, 0.96 L/month for JFB, and 4.66 L/month for LFB. • 2039 Baijiu selected from China were analyzed for EC exposure and risk assessment. • EC had a high incidence (73.6%) in Chinese Baijiu. • Drinks who preferred SFB had higher EC intake. • Geographical differences influence EC formation. • MOEs showed the EC in SFB and JFB can cause cancer risk for drinkers. [ABSTRACT FROM AUTHOR]

• Baijiu vintage analysis was achieved by targeted GC and non-targeted 1H NMR. • Three variable selection methods were used to decrease input variables. • PLSR vintage model was optimized to have robust prediction performance. • Ten components were found as potential vintage markers for Chinese Baijiu. Economical-driven counterfeit and inferior aged Chinese Baijiu has caused serious concern of publicity in China. In this study, a total of 167 authentic Chinese Baijiu samples with different vintages including 3 flavor types were carefully collected. Gas chromatography (GC) was used to determine main volatile components and proton nuclear magnetic resonance (1H NMR) spectroscopy was employed to obtain non-targeted fingerprints of Chinese Baijiu samples. Partial least squares regression (PLSR) models, which were confirmed by internal and external validation, were established for effectively identifying actual storage vintage of Chinese Baijiu with various brands, flavor types. Centering (Ctr), pareto scaling (Par), unit variance scaling (UV) data pretreatment methods, principal components (PCs), and three modified variable selection methods were proposed to successfully optimize the vintage model and effectively extract important vintage characteristic factors. This study demonstrated that NMR and GC combined with multivariate statistical analysis are effective tools for validating vintage authenticity of Chinese Baijiu. [ABSTRACT FROM AUTHOR]

• Residue levels of eighteen pesticides during Chinese Baijiu production were assessed. • Pesticide residues were obviously removed in steeping and steaming step. • Fermentation reduced pesticide residues by 39.8–74.2% owing to microbial degradation. • Distillation step was proved to be effective for decreasing pesticide residues. • PFs of eighteen pesticides were clarified during Chinese Baijiu production. The fate of eighteen pesticides in field-collected rice samples during Chinese Baijiu production was systematically studied. The results indicated that steeping decreased flonicamid residue by 73.2% due to its high water-solubility and low octanol/water partition coefficient. The steaming step reduced pesticide residues by 32.0%–75.3% through evaporation or thermal degradation. After steaming, the pesticide residues were further reduced by 39.8–74.2% in fermentation which might be caused by biological degradation. In addition, distillation was shown to be most effective, responsible for greater than 90% losses of the remaining pesticide residues. The processing factors (PFs) were generally lower than 1 for different processes and the whole procedure. These results revealed that the procedure of Chinese Baijiu production could dramatically decrease residues of all the eighteen pesticides. Overall, this study provide important references for monitoring pesticide residue levels during the production of Chinese Baijiu from rice, and ensuring proper risk assessment from pesticide contamination. [ABSTRACT FROM AUTHOR]

[Display omitted] • The temporal perception of pungency of Baijiu were evaluated by TI and TDS. • Baijiu with different aging times differed in their temporal profiles of pungency. • Pungency differences of Baijiu were related to both intensity and sub-qualities. • TI and TDS supplied more valuable information of temporal differences, which were not identified using static methods. Pungency is increasingly being recognized as an important factor of overall sensory quality, palatability, and consumer preference of distilled spirits. The characterization of pungency is necessary to evaluate the potential sensory quality of distilled spirits. In this study, the temporal profiles of pungency of Baijiu with different aging times were evaluated using time-intensity (TI) and temporal dominance of sensations (TDS) methods, considering both pungency intensity and pungency sub-qualities. TI results indicated significant differences in release rate of pungency during Baijiu consumption. Compared to young Baijiu, old Baijiu tend to show higher release rate of pungency, the areas under the curve and duration of pungency were significantly decreased in old Baijiu. The TDS results showed significant differences in the combination of dominant sub-qualities, as well as in the maximum dominance rates and the dominant duration of sub-qualities among Baijiu. The young Baijiu were mainly characterized by the dominant sub-qualities of "burning" and "numbing", whereas for old Baijiu, "burning", "prickle", and "drying" were dominant. The application of TI and TDS provided dynamic and temporal profiles of pungency to fully characterize pungency differences of distilled beverages. [ABSTRACT FROM AUTHOR]

• Effects of mechanization on microflora and flavor in Baijiu production were studied. • Pichia kudriavzevii was more active than Saccharomyces cerevisiae. • Five core microbes were detected both in metagenomic and metatranscriptomic analyses. • The expression level of 9 genes related to higher alcohol formation were determined. Microorganisms play an important role in the flavor formation of Chinese Baijiu. Mechanization is the way to develop Baijiu. Therefore, it is necessary to study the effects of mechanization on microbial community and flavor in Baijiu production. The microbial communities exhibited differences between two technologies with the fermentation, and the numbers of yeasts and bacteria in new mechanical technology were significantly higher than those in traditional technology at the peak of fermentation. Both metagenomic and metatranscriptomic analyses showed 5 core microorganisms in the fermentation, namely Saccharomyces cerevisiae , Rhizopus delemar , Pichia kudriavzevii , Lactobacillus helveticus , and Rhizopus oryzae. S. cerevisiae was generally regarded to be the most dominant yeast in Baijiu fermentation, but our metatranscriptomic data showed that P. kudriavzevii was more active than S. cerevisiae. These two analyses indicated that higher initiation abundance of S. cerevisiae and P. kudriavzevii and lower initiation abundance of R. delemar and R. oryzae were observed in traditional technology than in new technology, and that Lactobacillus displayed apparent advantages in traditional technology, whereas Lactobacillus and yeast exhibited obvious advantages in new technology at the end of fermentation. In addition to S. cerevisiae, other microorganisms including non-saccharomyces yeasts, molds, and bacteria were involved in higher alcohol formation. This work provides insight into the microbial dynamics and higher alcohol formation, as well as an efficient strategy for process improvement in Baijiu fermentation. [ABSTRACT FROM AUTHOR]

• Two l -cysteine high-producing Bacillus were inoculated in Baijiu fermentation. • l -cysteine content increased after Bacillus inoculation in Baijiu fermentation. • Bacillus inoculation increased 2-furfurylthiol contents in Baijiu. • Bacillus inoculation affected the microbial community structure. 2-Furfurylthiol was an important contributor to the flavor of traditional fermented foods including Baijiu. It is essential to increase 2-furfurylthiol concentration to improve the quality of Baijiu. This study aimed to enrich the content of 2-furfurylthiol in Chinese sesame-flavored Baijiu via two strains we isolated from Baijiu fermentation, Bacillus subtilis LBM 10019 and Bacillus vallismortis LBM 10020, which could respectively produce 56.31 mg/L and 42.81 mg/L l -cysteine, the precursor of 2-furfurylthiol, in sorghum extract. After inoculation of these two strains, the maximal relative abundance of Bacillus increased from 7.48% to 40.38%, the final content of l -cysteine increased by 101.44% in Baijiu fermentation. Moreover, the concentration of 2-furfurylthiol increased by 89.15% in the production. This work provides a novel strategy to improve the quality of Chinese sesame-flavored Baijiu. [ABSTRACT FROM AUTHOR]