The effects of different Zangqu from different regions on the physical and chemical indicators as well as the flavor of Tibetan traditional Qingke wine were studied by conducting simulated brewing experiments. The results showed that all Zangqu could successfully brew Qingke wines. There were no significant differences in the alcohol content, residual sugar, and free amino acid in Qingke wines, but the total acid content was significantly different. The main organic acids in brewed Qingke wines were lactic acid, acetic acid, and succinic acid. The total organic acids in Qingke wines made from Zangqu of Lasa and Rikaze regions were significantly higher than those in other regions. Total of 66 volatile aroma components were identified in different Qingke wines by HS-SPME and GC-MS, including 19 esters, nine aromatic compounds, 11 alcohols, nine acids, 10 aldehydes and ketones, eight others. The contents of aroma components in Qingke wines made from different regions’ Zangqu were significantly different. The flavor characteristics of Qingke wines could be regulated by the selection of Zangqu.

This study aimed to understand temperature changes in the fermented grains during liquor fermentation in underground vats. The temperature variation of the fermented grains was recorded by in situ temperature recorders. The effects of season, ambient temperature, and soil around the tank were compared. It was found that the temperature waves in winter were less than that in summer. The influences of soil were significant, the closer the grains to the surface vats wall, the lower the temperature. Furthermore, the temperature directly affected the liquor quality by influencing the physiochemical indexes of fermented grains. The contents of reducing sugar, acidity and alcohol were higher, and starch level significantly decreased at high temperature. This study provides a reference for designing mechanized liquor fermentation equipment.

This study revealed the correlation between the fermentation period and the quality of Chinese strong aroma-type Baijiu during five-month fermentation. The key flavor compounds and microbial community in fermented grains at the bottom layer were analyzed. It was found that lactic acid and acetic acid increased rapidly within 14 d of fermentation and followed by a moderate increase. Caproic acid, butyric acid and ethyl caproate gradually increased during fermentation. Lactobacillaceae sp. was dominant throughout the whole fermentation process, and the relative abundances of Ruminococcaceae sp. and Clostridiaceae_1 sp., two families with high abundances in pit muds, gradually increased. These results indicated that pit muds continuously provided anaerobic microorganisms for fermented grains during long-term fermentation, and these microorganisms played key roles in production of caproic acid, butyric acid and acetic acid. Although the abundances of anaerobic microorganisms originated from pit mud were low in fermented grains, they essentially contributed the flavor of strong aroma-type Baijiu, which provides a vital reference to control the quality of raw strong aroma-type Baijiu.

Volatile compounds in fermented grains (FG) and their corresponding pit muds (PM) from different spatial positions were analyzed by head space solid phase microextraction (HS-SPME) coupled with gas-chromatography mass spectrometry (GC-MS). The results showed that a total of ninety-seven compounds were quantified, including fifty-seven esters, ten acids, twelve alcohols, three aldehydes and ketones, twelve aromatics, and three other compounds. Highly similar volatile constitution was detected between cellar-wall FGs and PM samples. The level of volatile compounds detected in cellar-wall FGs was significantly higher than those in the cellar-central FGs. Meanwhile, major compounds in cellar-wall FGs were also identified in PM from the same layer with high quantities. This study revealed the influencing level between fermented grains and pit muds at different spatial layers, which may provide useful information for understanding substances recycling and the effects of microbes in cellar.

Daqu is an important source for bioactive compounds in Baijiu. Six novel compounds were isolated from Wuliangye Daqu by a set of chromatographic procedures. They were further identified by spectroscopic technology, including nuclear magnetic resonance (NMR) and mass spectrum (MS) etc. to be 5-n-nonadecylresorcinol, 5-n-heneicosyresorcinol, 5-n-tricosylresorcinol, (1E,22Z)-1,22-diferuloyloxydocoane, (1E,24Z)-1,24-diferuloyloxyteracosane, and (1E,26Z)-1,26-diferuloyloxyhexacosane. All 6 identified compounds were natural phenolic compounds observed for the first time from Daqu, and all of them exhibited significant antioxidant activities.

Daqu plays an important role in the brewing process of Baijiu (Chinese liquor) and it is the key factor determining the quality of Baijiu. However, there are few studies on the relationship between Daqu microorganisms and flavor compounds. The high-throughput sequencing technology was used to sequence the microorganisms in Daqu of Laobaigan-flavor Baijiu. At the same time, headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to detect the composition and change of flavor compounds in the process of Daqu making, and the heatmap of flavor components was drawn. By calculating Spearman correlation coefficients between microorganisms and flavor compounds, and between different microorganisms, the visualization network diagram was drawn. The results showed that 78 bacterial genera and 54 fungal genera were obtained in Daqu, among which the dominant bacteria genera were Lactobacillus, Weissella and Streptomyces, and the dominant fungi were Issatchenkia and Aspergillus; 5-15 d was the high yield period of flavor compounds, and 30-120 d was the synthesis period of important esters; the microorganisms that contribute greatly to the flavor compounds were Virgibacillus, unidentified_Cyanobacteria, Trichosporon, Cochliobolus, Oceanobacillus and Candida. Based on the analysis of the microbial diversity during the Daqu making of Laobaigan-flavor Baijiu, the bacteria which contribute a lot to the flavor components were identified, thereby achieving the purpose of helping to improve the quality of liquor and the standardized production of Daqu.

This research studied the effects of β-glucan on traditional highland barley wine fermentation. The dynamic changes in total sugar, β-glucan, and ethanol during fermentation, as well as the distribution of nutrients in traditional highland barley wine and distiller's grains were investigated. It was found that the total sugar content in the wine cellar increased first and then decreased, the β-glucan content gradually decreased while the alcohol content gradually increased, and some β-glucan dissolved into the highland barley wine with increasing fermentation time. On the other hand, the distiller's grains were enriched with protein, crude fiber, total sugar, β-glucan (8.42 g/100g), and amino acids (16 570 mg/100g). Moreover, the starch hydrolysis rate, the level of reducing sugar, and the amount of alcohol produced decreased significantly with increasing β-glucan (P<0.05). Besides, β-glucan was partially degraded during alcoholic fermentation. In conclusion, the encapsulation effect of β-glucan on starch delayed or inhibited starch hydrolysis dose-dependently. This study provides a scientific reference for improving the brewing quality of traditional highland barley wine and also for high value utilization of distiller's grains.

Luzhou-flavor Baijiu is one of the largest Baijiu types in production and sales in China. The traditional mud cellar fermentation method is unsuitable for mechanized operation and thus labor-intensive, and the original Baijiu often has the smell of pit mud. In order to produce Luzhou-flavor Baijiu without cellar mud, the fermentation broth of caproic acid was produced by cultivating pit mud microorganisms separately, and then mixed with fermented grains. The preparation of caproic acid fermentation broth was prepared by liquid anaerobic culture, and after 9 d fermentation, the content of caproic acid reached about 10 g/L and the content of butyric acid 2 g/L. Fermented grains were prepared in so-called pre-fermentation, which is traditional solid-state fermentation with a duration of 6-8 d according to physical and chemical parameters such as the content of alcohol and residual starch. Then a post-fermentation was conducted by mixing 0.04 g caproic acid fermentation broth with 100 g pre-fermented grains, till the total fermentation period was 42 d. The product prepared by this process has a soft and sweet favor, outstanding aroma of ethyl caproate, and typical style of high-quality Luzhou-flavor Baijiu.

In terms of understanding the relationship between wheat quality and Daqu quality, eleven quality indexes and twelve Daqu indexes at five fermentation stages from five wheat varieties were evaluated by variance analysis, regression analysis and principal component analysis. The results indicated that significant differences (P<0.05) were observed in quality traits and Daqu quality indicators between different wheat varieties. The grain bulk density, fat content, absorption rate, wet gluten content, and sedimentation value were positively correlated with the increase of protein content in Daqu, while the grain protein content was negatively correlated with liquefaction power and esterification power. Multiple stepwise regression analysis showed that the saccharification power of Daqu was mainly affected by fat content, sedimentation value and starch content, the liquefaction power was affected by bulk density and starch content, the fermentation power was affected by 1 000-grain weight, bulk density and starch content, and the esterification power was affected by bulk density and starch content. The cumulative variance contribution rate of the first three principal components was 74.57%. “Changmai 34” and “Shumai 691”, which were selected by principal component analysis with higher starch content and bulk density, were more suitable for Daqu production. The present results confirmed the wheat quality traits that affecting Daqu quality, established a new method to evaluate raw grain materials, and provided reference for specific end-use variety breeding and Daqu manufacturing process optimization.

The water-soluble peptides in distilled spent grains were isolated by ultrafiltration, and separated by reversed-phase high-performance liquid chromatography(RP-HPLC). The total of 30 peptides were identified by ultra-performance liquid chromatography coupled quadrupole time-of-flight mass spectrometry(UPLC-Q-TOF-MS), including 6 angiotensin converting enzyme inhibitory peptides and 2 antioxidant peptides. The results indicated that there were lots of biologically active peptides in the distilled spirits.

This study aimed to produce highland barley Xiaoqu products with Tibetan characteristics while ensuring flavor stability of highland barley wine products. The traditional culture method was used to separate, purify and identify microorganisms collected from 21 highland barley Xiaoqu samples, followed by transparent circle and starter-making screening. The results showed that a total of 278 strains were isolated and purified from Tibetan highland barley Xiaoqu, including six species of bacteria: Bacillus cereus, Bacillus safensis, Bacillus pumilus, Bacillus thuringiensis, Bacillus amyloliquefaciens, and Kocuria marina. Besides, there were 13 fungi identified, including Saccharomycopsis fibuligera, Saccharomyces cerevisiae, Saccharomycopsis malanga, Rhizopus oryzae, Coriolopsis trogii, Mucor circinelloides, Mucor racemosus, Irpex lacteus, Lichtheimia corymbifera, Aspergillus oryzae, Aspergillus flavus, Aspergillus niger, and Trametes hirsute. R. oryzae M12 with a saccharifying power of (1 382±77.38) mg/(g·h) and B. amyloliquefaciens Q4 with a protease activity of (1 035.56±40.09) μg/(g·min) were obtained by secondary screening. This study provides a research basis for optimizing starter-making process and improving the quality of highland barley wine.

This study was conducted to reveal the relationship between Thermoactinomyces as well as their functional genes and the physicochemical properties of Daqu which could provide technical support for analyzing the specific functions and directional control of microorganisms and high temperature Daqu in Baijiu fermentation. The diversity and dynamic changes of Thermoactinomyces and their functional genes in high temperature Daqu used in sesame-flavored Baijiu were investigated using metagenomic sequencing technology. The results showed that the relative abundance of Thermoactinomyces was significantly positively correlated with Daqu temperature. As Daqu temperature rising, the potential heat resistance genes, such as Clp (K03695), groEL (K04077), and pstB (K02036) in Thermoactinomyces enriched into dominant genes and were significantly positively correlated with Daqu temperature, which could effectively promote Thermoactinomyces surviving at high temperature. Moreover, the fermentation time of Daqu was significantly positively correlated with CZAy annotated genes, saccharification and esterification power. Glycosylhydrolases and glycosyltransferases genes were also positively correlated with saccharification and esterification power of Daqu significantly. These indicated that the abundance of Thermoactinomyces increased during the fermentation of Daqu, and the genes related to carbohydrate degradation were gradually enriched, which promoted the saccharification and esterification power of Daqu.

To reveal the effects of various physicochemical factors on pit mud bacteria and their correlations, differences in physicochemical factors and total bacteria count among degraded, normal, and high-quality Nongxiang flavored pit mud were investigated. The results revealed that the contents of moisture, ammonium nitrogen, calcium, and iron in these three pit mud exhibited significant differences (P<0.05). The contents of calcium and iron in degraded pit mud were 1.90-6.65 and 6.56-24.95 times higher than that in normal and high-quality pit mud, respectively, while other physicochemical indicators showed opposite results. There were no significant differences in pH, humus, available phosphorus and potassium, magnesium, and total bacteria count between degraded and normal pit mud (P>0.05). Compared with high-quality pit mud, there were marked differences in normal pit mud (P<0.05) except magnesium. Principle component analysis (PCA) showed that physicochemical factors in pit mud had clear correlations with the quality of pit mud. The relevance results indicated that the total bacteria count in the pit mud was positively correlated with moisture, pH, ammonium nitrogen, available phosphorus, humus, and available potassium, while it was significantly negatively correlated with the contents of magnesium, calcium, and iron.

Direct injection gas chromatography technology was used to quantify the 48 characteristic flavor components in fragrant Baijiu in order to authenticate the bottled storage year of fragrant Baijiu.Partial least squares regression (PLSR) combined with multivariate statistical methods was used to establish the prediction model of bottled storage year of fragrant Baijiu.The R² of the model was 0.953 4,the root mean square error of calibration (RMSEC) was 0.215 9,the root mean square error of prediction (RMSEP) was 0.838 4,and the relative percent deviation (RPD) was 4.631 3.The research results showed that both the regression fitting effect and the prediction accuracy of the model were good.The jack-knife method was used to test the significance of the regression coefficient of the PLSR model and screen out the characteristic markers of bottled storage year of fragrant Baijiu.The research results showed that ethyl hexanoate,acetaldehyde,ethyl caprylate and normal butanol were significantly correlated with the bottled storage year of fragrant Baijiu.

When brewing Gujing Tribute liquor, a large number of Lactobacillus acetotolerans were found in both pitmud and Zaopei. Therefore, it is important to rapidly detect L. acetotolerans specifically. In this paper, whole genome sequences of Lactobacillus bacteria and PRIMER-BLAST method were used to design L. acetotolerans-specific primers. Two pairs of primers were confirmed with decent specificity and combined with quantitative polymerase chain reaction (qPCR) to rapidly measure the amount of L. acetotolerans with different qualities and at different fermentation stages in pitmud and Zaopei. The results showed that the population of L. acetotolerans in Gujing Tribute pitmud was apparently lower than that of Zaopei and was apparently lower in old pitmud than that in pitmud of new plant. Moreover, L. acetotolerans in Zaopei from both new and old plants were generally high with apparent fluctuations among samples. In general, QPCR mediated by L. acetotolerans-specific primers can be used for L. acetotolerans quantification and facilitate quality assessment of pitmud or Zaopei in strong-aroma liquor production.

In order to determine metabolism rate of ethanol in human body, breathalyzer was used to track and detect volunteers after drinking beer, wine, and Baijiu(Chinese liquor). The results showed that the average metabolic rate of all volunteers was Baijiu>red wine>beer, and the metabolism rate in the first 2 h was highly positive correlated with that of the following 2 h. Through the analysis of the skeleton flavor substances of typical beer, wine and Baijiu, it was found that alcohols, such as N-propanol, furfuryl alcohol, propylene glycol, N-pentanol, β-phenylethanol were the key flavor substances that affected the early metabolism rate, and N-propanol was the most significantly flavor substance that decreased the metabolism rate.

In order to improve the cleaner production of rice-flavor Chinese liquor and to make the process energy-saving with low emission, this paper designed and studied the heating and water resources cycle based on the new mechanized brewing technology produces rice-flavor Chinese liquor. The results showed that after implementing the new mechanized process, the water consumption per unit of liquor decreased by 45% from 54 t/KL to 30 t/KL. The unit coal consumption decreased by 35% from 0.85 t/KL to 0.55 t/KL. Moreover, the labor cost reduced by 60%-70% while the yield of alcohol and liquor quality improved. Compared with the traditional strategy, the new strategy had a good heat exchange effect, which greatly shortened the distillation time. Besides, recycling cooling water was also realized, which not only achieved the desired effect but also saved resources.

The proteolytic rate of fermented grain is an important factor that affects flavor quality of sesame-flavor liquor. The level of proteolytic rate inevitably leads to differences in the final fermentation results of sesame-flavor liquor. To study the effects of proteolytic rate on fermentation process and original liquor quality, protein hydrolysates were directly added to the cellar fermentation system. The results showed that high proteolysis rate affected final physiochemical results of fermentation by catalyzing the occurrence of Maillard reaction and microbial synergistic metabolisms of yeast, Bacillus, and bacteria. In terms of liquor quality, high proteolytic rate mainly enhanced the aroma of the paste, increased the concentration of phenolic substances, and promoted the production of pyridines. Besides, high proteolytic rate was beneficial for producing thiazoles and dimethyl trisulfide during cellar fermentation. The overall effects of high proteolytic rate showed that the kind and concentration of flavor substances increased, with the concentration of pyrazines increased significantly in particular. However, the liquor flavor produced new defects. Therefore, a suitable rate of proteolysis has important effects on liquor quality. In addition, 2,4,5-trimethylthiazole was firstly discovered in sesame-flavor liquor.

The aim of this study was to explore the quality of medium-high temperature Daqu in different curved layers and the influence of the microenvironment during storage on the quality of Daqu. One-way ANOVA (analysis of variance) was applied to analyze the physicochemical and biochemical index values, sensory scores and typical flavor compounds of Daqu samples from different curved layers. And principal component and cluster analysis was used to compare the quality of different Daqu layers. The results showed that there was a significant difference in the moisture content between the top layer and the middle-upper layer, and a significant difference in the ammonia nitrogen content between the top layer and the middle-lower layer. Esterification capacity of Daqu in the middle-upper layer was quite different from that of middle-lower layer and bottom layer. The content of ethyl linoleic acid in the middle-upper layer was greatly different from that of the top layer. There were 14 typical flavor compounds in each curved layer, including ethyl hexanoate, phenylethyl alcohol, 2,3,5,6-tetramethylpyrazine and β-caryophyllen. But significant difference was not found among these flavor contents between different layer Daqu. Based on the results of principal component analysis of physiochemical and biochemical index values, sensory scores and typical flavor contents of Daqu, it is found that the quality of the middle-upper layer proves to be the best, while the other parts to be relatively poor. Moreover, the quality of Daqu in each layer can be clustered into different categories. Therefore, the quality of Daqu is difference in different curved layers.

Bacteria are one of the three major microorganisms for Baijiu fermentation. Bacteria that play important roles in the production of Baijiu includes: Bacillus, lactic acid bacteria, and clostridium etc. They produce trace amount of components such as esters, organic acids, pyrazines, terpenes. These components affect the flavor and quality of Baijiu. Because of the important functions of bacteria in Baijiu, and with the advancement in microbial isolation and culturing techniques, as well as in analytical detection techniques, researches on Baijiu fermentation have become more and more in-depth. This paper summaries recent research progress of functional bacteria in Baijiu, and introduces the main functional bacteria and their functions in Baijiu production, aiming to provide reference for future studies of functional bacteria in Baijiu.