Sensory quantitative descriptive analysis (SQDA) was used to analyze the flavor structure of nine samples of three aroma types (Nongxiangxing, Jiang-flavor and Zhima-flavor) of Shanzhuang Laojiu, and the results showed that there were significant differences in flavor and taste attributes among the aroma types. Liquid-liquid extraction coupled with gas chromatography-mass spectrometry (LLE-GC-MS) was used to analyze the composition of volatile compounds in these samples, and a total of 74 volatile flavor compounds were identified at high concentrations, manly including esters, alcohols and acids. Based on their aroma activity values (OAVs), 10 characteristic compounds contributing to the aroma of Shanzhuang Laojiu were identified. Partial least squares (PLS) analysis and correlation analysis were used to study the correlation between the sensory attributes and the characteristic aroma compounds, and the results showed that the Jiang, Qu and empty-cup aromas all had good correlation with acetic acid; ethyl butyrate, ethyl caproate, ethyl octanoate, butyric acid and capric acid were the main flavor compounds responsible for the alcoholic, ester, grain-like, sweet and fruity aromas; and the caramel-like and burnt aromas were highly correlated with ethyl myristate, ethyl oleate, ethyl linoleate and 2,3-butanediol. This study may lay the foundation for future research of the flavor formation mechanism of the three aroma types of baijiu.

Gas chromatography-ion mobility spectrometry (GC-IMS), gas chromatography-flame ionization detector (GC-FID), gas chromatography-mass spectrometry (GC-MS) and sensory evaluation were used to study the chemical flavor and sensory characteristics of sauce-flavor baijiu from four different origins in China. Totally 152 volatile compounds were identified, including esters, alcohols, ketones, and aldehydes. Through partial least squares discriminant analysis, 17 differential markers with variable importance in projection (VIP) value greater than 1 were selected from the 39 main volatile compounds to distinguish sauce-flavor baijiu from different origins. Sensory evaluation showed differences in the flavor characteristics of baijiu samples from the four origins which could be effectively identified by sensory evaluation and gas chromatography (GC). This study also clarified the material basis of the flavor difference, whose results provide a theoretical basis for the design of sauce-flavor baijiu body.

The cellar is the fermentation equipment and the main habitat of functional microorganisms for traditional Nongxiangxing Baijiu, and the quality of cellar mud largely determines the quality of Baijiu. Long-term practice and a large number of studies have shown that among the three major indicators that determine the quality of pit mud, the physicochemical factors are the basis, the microbial communities are the core, and the sensory indicators are the guide. The former two are interdependent and interact with each other, jointly acting on the last one. This paper presents a comparison of the research methods and findings on cellar mud quality in recent years in order to provide a quick overview of the cellar mud quality evaluation system and research evolution for the industry and to facilitate the production and subsequent research of Nongxiangxing Baijiu.

In order to improve the thermal stability of cutinase AFLACUT-2, the mutants were predicted and screened based on the change of free energy (ΔΔG) for protein folding, and the enzymatic properties of the selected mutant were characterized. The results showed that the thermal stability of mutant Q163M was significantly improved without affecting the enzymatic activity, which retained 86.09% of its activity when incubated at 40 ℃ for 168 h, compared with that of the wild-type strain. At 60 ℃, the half-life of the mutant was 1.68 times higher than that of the wild-type strain. In addition, compared with the wild-type strain, mutant Q163M showed better tolerance to an acidic environment. The mechanism for improved thermal stability of mutant Q163M was elucidated by intermolecular forces and molecular dynamic simulation. These results provide a basis for rationally modifying the thermal stability of cutinase and improving its capacity for the aqueous-phase synthesis of flavor ester at high temperature.