Traditional Chi flavor Baijiu contains high unsaturated fatty acids after steeping and aging with fat meat, which is easy to be oxidized during storage and cause rancidity. In order to reduce the unpleasant smell, coconut meat with low content of unsaturated fatty acid was used instead of fat meat for steeping and aging of Zhaijiu (raw liquor). The fatty acids in coconut and fat were methylated and then analyzed by GC-MS. The results showed that the content of unsaturated fatty acids in coconut meat was 9.53%, only 21.40% of that in fat meat (44.53%). When comparing the aging effects of different infiltration materials, the transmittance of the aged liquor with raw or cooked coconut meat was better than that with fat meat, the content of unsaturated fatty acids decreased by 26.09% and 30.21% respectively, and the stability of the liquor body was increased. The optimal aging process was: coconut addition of 200 g/L Zhaijiu, aging time 2.5 months. Under these conditions, the liquor was clear and transparent, with mellow taste in mouth and refreshing after taste. At the same time, coconut gave elegant coconut flavor to the finished liquor, which improved the quality of the Chi flavor Baijiu.

A novel method was developed for measuring alcohol content in Chinese Baijiu using proton nuclear magnetic resonance spectroscopy (¹H NMR). In this method, a fitting curve of ethanol concentration vs the integral ratio of methylene and water hydroxyl peaks was established, and the correlation coefficient was R²=0.994 7. At the same time, a working curve was prepared on account of methyl peak position, the correlation coefficient was R²=0.991 8. The linearities of both curves were good. The concentration obtained by ¹H NMR was less than 0.02 compared with the labeled value, which met the requirements of current food safety standards. This method exhibits a fairly good analytical performance and saves time, which is easy to operate when dealing with a batch of samples for enterprises and testing departments.

Strong-flavor Baijiu is manufactured via solid-state fermentation by a mixture of various microorganisms, and the interaction of these microorganisms provides Baijiu with unique flavors. Ethyl caproate is one of the main flavor compounds. Therefore, caproic acid-producing bacteria are generally considered as the most important functional microorganisms in strong-flavor Baijiu brewing. The present review summarizes the species and characteristics of caproic acid-producing bacteria reported so far and systematically expounds the metabolic pathways and competitive pathways of caproic acid. Besides, it introduces the regulation strategy of caproic acid metabolism in caproic acid-producing bacteria and the construction of caproic acid metabolic pathway. At the same time, the relationship between caproic acid-producing bacteria and other microorganisms in the strong-flavor Baijiu ecosystem is analyzed, and the application status of caproic acid-producing bacteria in Baijiu brewing and other industries is summarized. Furthermore, the application prospect of caproic acid-producing bacteria in Baijiu brewing is discussed, and it is pointed out that the microbial structure adjustment of the cellar needs to be studied in-depth, in order to provide a theoretical basis for further increasing the scientific nature of Baijiu brewing and improving Baijiu quality.

Analysis of Brewing Industry (experiments included) is the core course in Brewing Engineering major in Jiangnan University. This course is both hard to teach for teachers and to learn for students due to its strong comprehensiveness and applicability. To achieve the objective of this course, the teachers team incorporated the concept of outcomes-based education (OBE) into the teaching contents and teaching organization of Analysis of Brewing Industry (experiments included). We included moral education, the latest techniques and high-quality teaching resources in the teaching contents, and constructed the “pre-class preparation-notes in class-summary after class-scientific evaluation” class organization mode during teaching. A variety of teaching methods, such as case discussion, were also adopted. Moreover, a close-loop “Teaching-Feedback-Improvement” strategy was established to continuously improve the teaching efficiency. Based on the above methods, students will have solid theoretical foundation and grasp the ability to solve complicated engineering problems.

To reveal the metabolism characteristics of higher alcohols produced by microbiota in fermentation process of light aroma type Baijiu started by Xiaoqu, gas chromatography flame ionization detection (GC-FID) was used to analyze the dynamics of higher alcohols during the fermentation process of two seasons. High-throughput amplification sequencing revealed the succession of microbial community during the fermentation process. Subsequently, the differences between microbial communities of the two seasons were analyzed via random forest method. Finally, mechanism of synthesis and regulation of higher alcohols were determined by correlation analysis with simulated solid-state fermentation. The total amount of higher alcohols produced in the samples of spring was (179.43±9.57) mg/kg, and the yield was higher in that of autumn, reaching (276.86±26.80) mg/kg. Saccharomyces, Pichia, Rhizopus, Lactobacillus and Weissella were the differentiate genera among the predominant microorganisms in the two-season samples. Among them, Saccharomyces, Pichia and Lactobacillus had significant correlation coefficients with the yield of higher alcohols (ρ>0.6, P<0.05). Saccharomyces cerevisiae produced (43.52±2.43) mg/kg higher alcohols in simulated solid fermentation. Besides, Pichia kudriavzevii and Lactobacillus brevis produced lower levels of higher alcohols (<3 mg/kg). The yield of higher alcohols produced by coculture system was 8.49 mg/kg lower than that of S. cerevisiae (P>0.05), suggesting that P. kudriavzevii and L. brevis could regulate the synthesis of higher alcohols. The regulation microorganisms could effectively control the synthesis of higher alcohols during the fermentation process. This study has guiding significance for the production of high-quality light aroma type Baijiu started by Xiaoqu with low content of higher alcohols and provides a theoretical basis for the flavor regulation of fermented food.

A strain of Bacillus subtilis isolated from strong-flavor Daqu was fermented by solid-state mixed bacteria to study the effect of B.subtilis on the structure and function of microbial flora under different conditions.With the fermentation conditions of strong-flavor Daqu at different stages,the temperature/humidity was 25 ℃/95%,35 ℃/85,43 ℃/70,50 ℃/60,58 ℃/40%,respectively.The disturbance of B.subtilis to the structure and function of microbial flora was studied by solid fermentation of raw materials with wheat as medium.The results showed that the disturbance of B.subtilis could increase the richness and diversity of bacteria at higher temperature,while the fungi decreased slightly;the effects on dominant genera in solid mixed bacteria fermentation system were mainly reflected in the increase of relative abundance of Bacillus and Pichia under 35 ℃/85% and 43 ℃/70% fermentation conditions.The relative abundance of unspecified-Aspergillus,Enterobacter and Lichtheimia was increased under 25 ℃/95% and 50 ℃/60% fermentation condition;and the metabolic pathways related to amino acid metabolism were significantly changed.It can be seen that inoculation of B.subtilis will disturb other microorganisms in solid mixed fermentation system and affect microbial metabolism in the system,and it provides important data for further study of the application of B.subtilis in strong-flavor Daqu.

Reactive carbonyl species (RCS) are toxic and highly reactive materials in liquor fermentation process which bring potential safety hazards to liquor products. In this study, a high performance liquid chromatography analysis method was established to simultaneously determine acrolein, methylglyoxal, crotonaldehyde, 5-hydroxymethylfurfural, formaldehyde and acetaldehyde in Chinese Baijiu. A comprehensive analysis of different flavor liquor samples and wine samples during processing was carried out. The diluted sample was derivatized with 2, 4-dinitrobenzene hydrazine at 50 ℃ for 1.5 h. A Beconsil C₁₈ chromatographic column (250mm×4.6 mm, 5 μm) was used. The mobile phase was acetonitrile and water under gradient elution at a flow rate of 1.0 mL/min. The column temperature was set to 40 ℃, and the diode array detector was selected as dual-channel detection, with detection wavelength of 360 nm (ACR, MGO, CRO, FOR, ACE) and 400 nm (5-HMF), respectively. This method exhibited good linearity with correlation coefficients all above 0.999. The detection limits were in the range of 1-8 ng/mL and the quantitate on limit were in the range of 3-25 ng/mL. The spiked recoveries ranged from 85.39%-105.78%, with RSDs less than 4%. The level of RCS in Maotai-flavor Baijiu and sesame-flavor Baijiu was higher, which was speculated to be related to the high temperature fermentation. In the process of 8 rounds of fermentation and 7 times of liquor extraction, the RCS concentration in Maotai-flavor Baijiu was the highest in the 3rd, 4th and 5th rounds. The RCS of strong-flavor liquor rose to the highest in the process of “accumulation out of cellar”, and the RCS level in the sample of “the double bottom of liquid fermentation” and “the middle layer of liquid fermentation” were ranked first and second, respectively. Our method is stable and sensitive, which is easy to operate, and suitable for detecting RCS in liquor and semi-finished products in fermentation processing.