Yeasts and their importance to the flavour of traditional Chinese liquor: a review

As one of the three major distilled spirits in the world, traditional Chinese liquor has a distinctive aroma and taste. The brewing process typically involves two stages: the Daqu‐making process and the liquor‐making process. Further, it commonly adopts solid state fermentation in an open environment, which involves diverse microorganisms such as bacteria and fungi. Yeasts, as an integral brewing microorganism, are not only a dominant force in the fermentation process but also play a key role in the quality and character of different flavour liquors. Studies on yeasts associated with Chinese liquor have rarely compared them with those associated with other alcoholic beverages (wine, sake, etc.), especially in the microbiome‐related flavour of the alcoholic beverage. Here, we review the Chinese liquor brewing process, the yeast community in the brewing process, the yeast derived flavour compounds, the interaction between yeasts and other microorganisms and gene level modifications. © 2019 The Institute of Brewing & Distilling     

The production of the Chinese baijiu from sorghum and other cereals

Baijiu is a widely consumed spirit usually distilled from fermented sorghum. Here the use of other cereal grains (wheat, corn, rice and barley) is compared with sorghum. The concentration of ethyl acetate in spirit made from sorghum was found to be higher than in the spirits made using other grains, whereas the concentrations of aldehydes and higher alcohols were lower. Based on sensory evaluations, the flavours were more satisfactory when sorghum was used for making Baijiu. Of the other cereals, the flavour from wheat was better than those of corn, rice and barley for making Baijiu. The ester concentration of the spirit made from the rice was low, whereas aldehyde and alcohol contents were high. An abnormal flavour was found in spirits made from corn or barley. Further work with sorghum showed variations in tannin content, and a correlation between the tannin content and brewing performance. When the content of tannin was <1.94%, the ethyl acetate and ethyl octanoate content were positively correlated with tannin content. In contrast, the ethyl lactate and higher fatty acid ethyl esters content were negatively correlated with tannin content. The results of flavour analysis and sensory evaluation indicated that the ideal sorghum tannin content for producing Baijiu was between 1.0 and 2.0%. Copyright © 2017 The Institute of Brewing & Distilling     

Sesame flavour baijiu: a review

Sesame flavour baijiu is an important style of Chinese liquor (Baijiu). However, the characteristic flavour substances of sesame flavour baijiu and associated microbial metabolic mechanisms are unclear. In recent years, research on sesame flavour baijiu has grown. This review focuses on current studies on the brewing process, the diversity of microorganisms involved in fermentation and the important aroma compounds in sesame flavour baijiu. This review will be helpful in understanding the brewing process of sesame flavour baijiu, but also in highlighting measures for improving quality. © 2020 The Institute of Brewing & Distilling     

底醅串蒸工艺在浓香型白酒生产中的应用

利用窖池长、短发酵周期的底醅,结合酒甑蒸馏提香特点,在浓香型白酒生产中应用双轮底醅、普通底醅结合窖池中、上层酒醅的串蒸工艺,合理配醅串蒸;以充分利用酒醅中的风味物质,提高原酒特优率,同时探究浓香型白酒生产工艺与质量特征。结果表明,双轮底醅串蒸工艺在稳定出酒率的基础上,能有效提高原酒中特征性风味物质的含量,原酒特优率平均提高2.0%左右。     

高酸调味酒酿造研究综述

该文简述了现存酸性调味酒的生产工艺,进一步明确了有机酸是白酒综合质量、白酒口感的关键性制约成分。提出以固态法酿酒丟糟为原料,拌和生料粮粉进行晾堂堆积开放式培菌,配伍生香醪入泥窖密封发酵,出窖糟醅辅以生香醪复式蒸馏提香的新型酿造工艺,制备出高酸调味酒,用于白酒的勾兑调味。“以酒调酒”解决白酒酒体总酸偏低的问题,同时为丟糟资源的再利用提供了一条更合理、更具经济效益的途径。     

Lactic acid bacteria in the brewing of traditional Daqu liquor

Lactic acid bacteria and their metabolites play important roles in defining Chinese liquor flavour. Currently, the role of lactic acid bacteria in liquor brewing remains unclear. This review discusses the role of lactic acid bacteria in fermentation of different types of Daqu and fermented grains. It focuses on the interaction between these bacteria and other microorganisms during liquor brewing, and analyses its effect on liquor flavour and quality. In addition, the roles of Lactobacillus in reducing the amount of unfavourable ingredients in liquor and the succession law of lactic acid bacteria during the fermentation of three Daqu liquors were also studied. Finally, the methods aimed at reducing lactic acid production and improving liquor quality are discussed. Overall, the review highlights the significance of lactic acid bacteria for brewing Daqu liquor. Nevertheless, further studies are required to clarify the role and mechanism of action of lactic acid bacteria during liquor fermentation. © 2019 The Institute of Brewing & Distilling     

宜宾产区浓香型白酒酿造生境中细菌的群落结构

该文利用高通量测序技术全面解析宜宾产区浓香型白酒酿造生境中的微生物菌群结构,并对窖泥、大曲、酒醅和黄水中的细菌种类和丰度进行对比分析。结果表明,从宜宾产区白酒酿造生境的26个样品中共注释到来自于201个属的1493个OTUs,主要分布于拟杆菌门(Bacteroidete)、变形菌门(Proteobacteria)和厚壁菌门(Firmicutes),其中5个属来自于古菌域的广古菌门(Euryarchaeota)。窖泥样品中微生物菌种的多样性最高,主要以古菌、瘤胃球菌和乳酸菌为主;大曲的多样性次之,主要包括未鉴定到属水平的细菌,芽胞杆菌、乳酸菌和高温放线菌等;酒醅和黄水中的微生物多样性最低,其主要微生物类群以乳酸菌和瘤胃球菌为主。宜宾产区浓香型白酒酿造过程微生物群落结构呈现出从多种微生物共同作用到功能微生物主要发挥作用的趋势。该研究为探究浓香型白酒酿造过程中功能微生物,解析白酒酿造机理,提升白酒品质奠定了基础。     

Effects of different distillation patterns on main compounds of Chinese Luzhou‐flavour raw liquors

This study aimed to investigate the effects of different distillation patterns on main compounds of Chinese Luzhou‐flavour liquor. Results showed that more volatiles of raw liquor might originate from fresh grains for a newly constructed pit. A modest (p  = 0.05) increase in the total amount of volatiles was found in the heart liquor from fermented grains added to fresh grains and rice hulls to distillate (AG pattern), reaching a maximum value of 1012.22 mg/L. The percentage of esters in the AG pattern ranged from 81.22 to >95.03% compared with samples from fermented grains only added to rice hulls to distillate (NG pattern). Acids in the heart liquor obtained by the AG pattern were higher than those for NG, but the corresponding proportion was opposite. Alcohols were detected at ~1.62% in NG pattern but were 1.42% in AG. Cyanide and ethyl carbamate content in the head liquor were far higher than those in the heart and tail liquor. In particular, cyanide content dramatically increased after adding fresh grains during the distillation process. Copyright © 2017 The Institute of Brewing & Distilling     

High throughput sequencing of the bacterial composition and dynamic succession in Daqu for Chinese sesame flavour liquor

Sesame flavour liquor is a traditional Chinese distilled spirit with fruity, sweaty, roasted sesame and floral aromas. High temperature Daqu production is one of the key processes in the formation of sesame flavour liquor. The composition and changes in the microbial community during the making of Daqu have a significant impact on the quality of Daqu liquor. In this study, microbial diversity based on high throughput sequencing technology was used to reveal the bacterial community structure and succession law in the four critical stages of high temperature Daqu production. The results show that Firmicutes had a significant advantage (76.7%-98.2%) in the four stages as Proteobacteria and Actinobacteria reached peak values in the first and second periods, and decreased in the later periods. At the genus level, Kroppenstedtia, Lactobacillus, Weissella, Lentibacillus, Bacillus and Saccharopolyspora were detected as the main bacterial groups in the high temperature Daqu of Chinese sesame flavour liquor. The abundance of Lactobacillus and Weissella was greater than that of other microbes in the Daqu entry period. During the first Daqu flipping, the number of bacterial genera reached a peak in the production process. Then, the bacterial diversity continued to decrease until the last period, while Kroppenstedtia, Saccharopolyspora and Lentibacillus adapted to the high temperature environment and accumulated during the second Daqu flipping and the Daqu exit. This research used high throughput sequencing technology to reveal, for the first time, the bacterial composition and dynamic succession in high temperature Daqu production of Chinese sesame flavour liquor. This work will contribute to a deeper understanding of the correlation between the formation of flavour substances in sesame flavour liquor and the microorganisms used in its production. © 2019 The Institute of Brewing & Distilling     

浓香型白酒封窖工艺研究进展

浓香型白酒是我国特有的酒种,一直深受广大消费者的喜爱,在中国白酒产业中具有举足轻重的地位。该文主要从封窖材料、操作工艺流程、劳动强度以及对酒质影响等方面对浓香型白酒酿造工艺中封窖工艺的研究进展进行了综述,阐述了目前行业中主要的四种封窖工艺及不同封窖工艺的优缺点,以期对浓香型白酒酿造工艺的传承与创新提供一定的借鉴与参考。     

金种子浓香型白酒压排前后的工艺分析与实践

浓香型白酒压排期发酵时间较长,带来酒醅酸度大、活性低等因素不利于转排发酵,影响出酒率与酒质等,压排前后各一排的生产尤为重要。通过对压排前、压排、转排等的工艺分析,合理调整各阶段的配醅、调醅、入池参数、窖池养护等工艺细节,以期实现降温、控酸、合理调控酒醅活性、产质量稳定等目的。结果表明,对工艺细节的合理调整可实现出酒率与酒质的稳定与提高。     

芝麻香型白酒酿酒微生物研究进展

芝麻香型白酒是我国传统白酒的创新香型之一,因其所具有的独特风味越来越受到消费者的喜爱,近年来对于芝麻香型白酒酿造过程中微生物的探索也成为白酒研究中的热点领域之一。该文系统综述了芝麻香型白酒酿酒微生物的多样性分析、产香味成分分析、酶活性研究以及酿酒微生物在芝麻香型白酒生产中应用的最新研究进展,并对芝麻香型白酒酿酒微生物的未来的研究与利用提出了思考与展望,为后续芝麻香型白酒酿酒微生物的相关研究提供必要的信息参考。     

淡雅芝香白酒的研制

近年来,各香型白酒在工艺和口感方面相互融合、取长补短是新的趋势。浓香型白酒产品市场占有率高,而芝麻香型白酒产品品质高雅。景芝酒业拥有芝麻香及浓香型白酒的生产技术优势。通过反复试验对比,总结出了"清蒸续米查、多粮泥窖、大麸结合、堆积发酵、分类贮存、多型勾调"的淡雅芝香白酒生产工艺要点。试验成功酿制出了色清透亮,香气幽雅,酒体丰满,细腻协调,绵柔爽净,回味悠长,具有独特景芝芝麻香风格的淡雅芝香白酒。     

中药材对清香型白酒主要酿造微生物及风味物质的影响

为筛选可提升清香型白酒酿造质量的中药材,探究了20种中药材对发酵微生物酿酒酵母（Saccharomyces cerevisiae）Y1、异常威克汉姆酵母（Wickerhamomyces anomalus）Y29和米根霉（Rhizopus oryzae）G1生长的影响。于绿衣观音土曲中添加中药材,模拟清香型白酒工艺进行固态发酵小试实验,分析中药材的添加对糖化醅中微生物数量及清香型白酒原酒中主要风味物质的影响。结果表明,添加杏仁和甘草等中药材可促进菌株Y1和Y29的生长,添加桂皮、杏仁等中药材可促进菌株G1生长。添加丁香、红景天对菌株Y1、Y29和G1的抑制作用明显,其最适添加量为0.5 g/L。川芎、辣蓼和人参分别使糖化醅中细菌、酵母和霉菌增殖的效果最佳,其微生物增长率分别为143.03%、47.69%和73.47%。气相色谱表明,茴香使清香型白酒乙酸乙酯含量增加32.44%,茯苓使清香型白酒杂醇油含量降低9.23%。     

Determination of volatile compounds in Baijiu using simultaneous chromatographic analysis on two columns

Baijiu is a Chinese spirit which is produced by a complex process involving solid state fermentation with various raw materials and a consortium of microorganisms resulting in an abundance of fermentation by products. A method was developed for quantification of 62 compounds in Baijiu spirits using simultaneous direct injection to two columns (CPWax-57CB and DB-624). Dual column analysis substantially increased the reliability of identification using a flame ionisation detector. The method had high linearity - for all but one compound - indicated by the coefficient of determination (R²) of ≥ 0.999 (in a range of 0.3 – 260 mg/L) and reproducibility (for the majority of compounds at a concentration of ca. 1 mg/L, < 5% for the DB-624 columns and < 8% for the CPWax-57CB column). The limit of detection was < 1 mg/L for all compounds. The method was used to analyse volatile compounds in 38 samples of Baijiu, from different regions and flavour types. The main group of compounds in the volatile fraction were esters and higher alcohols. Based on Orthogonal Partial Least Squares Discriminant Analysis it was not possible to separate the samples in terms of region, but it was possible to distinguish between strong and soy sauce types of Baijiu from the other samples. © 2020 The Institute of Brewing & Distilling     

Tetramethylpyrazine in Chinese sesame flavour liquor and changes during the production process

Tetramethylpyrazine (TTMP) is a key bioactive alkaloid and flavour compound found in Chinese sesame flavour liquor. Changes in TTMP concentration during the production of sesame flavour liquor have received little attention. Here, TTMP was tracked from raw material, fermented grains and fresh liquor in storage using high‐performance liquid chromatographic–tandem mass spectrometry (HPLC‐MS/MS). The results showed that TTMP was formed during stack fermentation, solid‐state fermentation and distillation, while no TTMP was produced during the storage process of fresh liquor. Furthermore, a higher temperature fermentation and bacterial starter culture were beneficial to TTMP generation. Accordingly, technology strategies for increasing the concentration of TTMP in sesame flavour liquor include raising the temperature of stack fermentation and distillation, reducing the distillation speed and screening for high TTMP producing Bacillus species. © 2018 The Institute of Brewing & Distilling     

白酒酿造过程中的微生物研究进展

在传统白酒酿造过程中,微生物对白酒品质、风味的影响至关重要。白酒的品质与酒中微生物的研究程度有着极为密切的关系,风味微生物更是影响白酒品质的关键因素。该文综述了白酒发酵过程中的微生物研究现状,主要概述了白酒发酵期间的细菌、酵母菌、霉菌的类别、作用机理及其变化过程,并揭示了现代分子生物技术下的白酒微生物菌群多样性,以期深入研究微生物与白酒风味形成之间的关系且为解析白酒发酵的本质奠定基础。     

微生物发酵产酯化酶在浓香型白酒品质提升中研究进展

该文概述酯化酶的特性,酯化酶在酯类合成中的重要作用,浓香型白酒酿造生产中微生物发酵产酯化酶在酯化大曲、黄水及酿造发酵过程中的研究应用情况。分析酯化酶对于提高浓香型白酒出酒率、优质酒率及减少用曲量等方面的积极效果,并对目前酯化酶在浓香型白酒酿造过程中存在的问题及其发展前景进行了讨论与展望,为酯化酶在浓香型白酒品质提升中的应用研究总结经验。     

微生物代谢组学及其在白酒酿造中的应用研究进展

微生物代谢组学是代谢组学的重要研究领域。该文主要对微生物代谢组学在微生物分类、代谢物分析鉴定、发酵工艺等领域的研究内容进行了总结,对其研究过程及应用的技术手段、在白酒酿造中对分析风味物质、优化酿造工艺的应用及存在的主要问题进行了综述,并对其发展趋势做出展望。研究微生物代谢组学及其在白酒酿造中的应用,为探究白酒风味形成机制、优化酿造工艺、提高原料利用率等提供了新的方法,有利于进一步揭示中国传统白酒的生产原理,提升白酒品质。     

Analysis of bacterial communities in pit mud from Zhijiang Baijiu distillery using denaturing gradient gel electrophoresis and high- throughput sequencing

Zhijiang Baijiu is a Chinese strong flavour liquor produced using a traditional Chinese solid state fermentation involving microorganisms in pit mud on cellar walls. In this study, pit mud samples were collected from three different cellars in a Zhijiang Baijiu distillery ranging in age from 10 to 20 and 30 years. The bacterial communities were analysed using denaturing gradient gel electrophoresis, high-throughput sequencing and quantitative real time PCR. These analyses showed that the diversity of the bacterial community in pit mud samples was relatively stable in cellars aged from 20 to 30 years old. High throughput sequencing also revealed that the relative abundance of seven core bacterial families and nearly half of the core bacterial genera were stable in 20 year-old cellars. In cellars of 10 to 30 years, the relative abundance in pit mud of Ruminococcaceae and Clostridium cluster IV increased, while that of Petrimonas and an unclassified Firmicutes decreased. Real time PCR showed that aged pit mud contained more bacteria and Clostridium kluyveri than young pit mud. It is concluded that the bacterial communities in aged pit mud are more suitable for producing high quality Baijiu. © 2019 The Institute of Brewing & Distilling