“Key Factor” for Baijiu Quality: Research Progress on Acid Substances in Baijiu

Research on the brewing technology of Dangshen Huangjiu with low biogenic amines and high functional factors

BACKGROUND

Biogenic amines (BA) are hazardous components in Huangjiu (HJ). To ensure the quality of Dangshen Huangjiu (DSHJ), an orthogonal experiment L9 (33) was proposed to optimize the process by the main brewing factors (pre-fermentation temperature, pre- and post-fermentation time) that may affect BA and functional factors in DSHJ. DSHJ was produced with low BA content and high functional factors. Gas chromatography-ion mobility spectrometry combined with a multivariate statistical method (GC-IMS-MSM) was used to analyze the volatile components in the brewing process of DSHJ.

RESULTS

The optimum brewing process parameters of DSHJ were as follows: pre-fermentation temperature, 28 °C; pre-fermentation time, 9 days; post-fermentation time, 18 days. The average content of BA in DSHJ was 33.12 mg L-1, and the sensory score, total phenol content and DPPH free radical scavenging rate of DSHJ were significantly higher than those of HJ. A total of 14 esters, 7 acids, 7 alcohols, 1 ketone, 5 aldehydes and 1 pyrazine in DSHJ and HJ were identified by GC-IMS. There were no significant differences (P > 0.05) in DSHJ and HJ in the soaking rice and saccharification stage. 11 components, such as ethyl acetate, and 12 components, such as acetic acid, were the different components of HJ and DSHJ in pre-fermentation and post-fermentation stages, respectively. In the post-fermentation stage, the contents of 8 components in DSHJ such as ethyl acetate were higher than in HJ.

CONCLUSION

The preparation process parameters of DSHJ optimized by orthogonal experiments can ensure that DSHJ has the advantages of low BA content, high total phenol content and good antioxidant activity. Sensory score and GC-IMS-MSM analysis found that DSHJ prepared using the optimal process had the characteristics of good taste and rich aroma. © 2024 Society of Chemical Industry.

A novel organic acids-targeted colorimetric sensor array for the rapid discrimination of origins of Baijiu with three main aroma types

Given the severe problem of Baijiu authenticity, it is essential to discriminate Baijiu from different origins quickly and effectively. As organic acids (OAs) are the most dominant taste-imparting substances in Baijiu, we proposed a simple, fast, and effective OAs-targeted colorimetric sensor array based on the colorimetric reaction of 4-aminophenol (AP)/4-amino-3-chlorophenol (ACP) under oxidation of Cu(NO3)2 for the rapid discrimination of origins of Baijiu with three main aroma types. Hydrogen ions ionized from OAs induced the protonation of the amino group, which blocked the colorimetric reaction, and the different levels of OAs in Baijiu enabled the array to discriminate different origins of Baijiu. The array was implemented to analyze 10 simple OAs and 16 mixed OAs and further for the discrimination of 42 Baijius with an accuracy of 98%. This method provided an efficient research strategy for a basis for rapid quality analysis of Baijiu.

Caproicibacter sp. BJN0012, a potential new species isolated from cellar mud for caproic acid production from glucose

Acids play a crucial role in enhancing the flavor of strong-aroma Baijiu, and among them, caproic acid holds significant importance in determining the flavor of the final product. However, the metabolic synthesis of caproic acid during the production process of Baijiu has received limited attention, resulting in fluctuations in caproic acid content among fermentation batches and generating production instability. Acid-producing bacteria found in the cellar mud are the primary microorganisms responsible for caproic acid synthesis, but there is a lack of research on the related microbial resources and their metabolic properties. Therefore, it is essential to identify and investigate these acid-producing microorganisms from cellar mud to ensure stable caproic acid synthesis. In this study, a unique strain was isolated from the cellar mud, exhibiting a 98.12 % similarity in its 16 S rRNA sequence and an average nucleotide identity of 79.57 % with the reference specie, together with the DNA-DNA hybridization of 23.20 % similarity, confirming the distinct species boundaries. The strain was able to produce 1.22 ± 0.55 g/L caproic acid from glucose. Through genome sequencing, annotation, and bioinformatics analysis, the complete pathway of caproic acid synthesis from glucose was elucidated, and the catalytic mechanism of the key thiolase for caproic acid synthesis was investigated. These findings provide useful fundamental data for revealing the metabolic properties of caproic acid-producing bacteria found in cellar mud.

GC/MS-based untargeted metabolomics reveals the differential metabolites for discriminating vintage of Chenxiang-type baijiu

The "outstanding and unique aged aroma" of Chinese Chenxiang-type baijiu (CXB)-Daoguang 25 (DG25) mainly originates from a "extraordinary storage technology" of Mujiuhai (a wooden container), so it is mysterious and interesting. In this study, an untargeted GC/MS-based metabolomics was used to reveals the volatile differential metabolites for discriminating six different vintages of DG25 combing with chemometrics. A total of 100 volatile metabolites (including unknowns) were extracted and identified, including esters (41%), alcohols (10%) and acids (7%) so on. Finally, 33 differential metabolites were identified as aging-markers. Among them, 25 aging-markers showed a downtrend, including 17 esters such as ethyl acetate, ethyl hexanoate and ethyl palmitate so on. Moreover, it was interesting and to further study that furans showed a significant downtrend. Statistically speaking, ethyl benzoate played an important role in discriminating vintage of 1Y and 3Y, and the other 24 differential metabolites with downtrend discriminating the unstored (0Y-aged) DG25. Eight differential metabolites, such as ethyl octanoate, benzaldehyde, 3-methylbutanol and 1,1-diethoxyaccetal so on increased during aging of DG25, and they played a statistical role in discriminating the 5Y-, 10Y- and 20Y-aged DG25. This study provides a theoretical basis way for the formation mechanism of aging aroma for CXB.

Unraveling the chemosensory characteristics dependence of sauce-flavor baijiu on regionality using descriptive sensory analysis and quantitative targeted flavoromics

Descriptive sensory analysis, headspace solid-phase microextraction-gas chromatography-mass spectrometry, gas chromatography-flame ionization detector and multivariate statistical analysis were used to elucidate the regional dependence of sauce-flavor baijiu (SFB). Although SFB samples from different regions couldn't be clearly classified by sensory profiles, they could be clearly divided into 5 groups in principal component analysis plot based on quantitative targeted flavoromics analysis. And then, the relationship between sensory attributes and volatile compounds were investigated by network analysis. Twenty regional aroma markers were identified by multivariate statistical analysis to distinguish SFB samples from different regions. Furthermore, the influence of manufacturing operation on SFB in Guizhou region was further analyzed. Thirty-eight potential compounds were significant different in Guizhou SFB samples with different manufacturing operations. This study not only provides a better understanding of regional dependence on SFB flavor, but also further clarifies the inheritance importance of manufacturing operation in traditional SFB production.

Coordination between scientific and technological innovation and the high-quality development of Baijiu industry: The coupling and decoupling perspective

The Baijiu industry is a significant contributor to both the food industry and the light industry. Its high tax characteristics effectively promote the sustainable development of the regional economy. First, the evaluation index system of scientific and technological innovation (STI) and high-quality development of Baijiu industry (HQDBI) were constructed. The entropy-improved CRITIC method was used to measure the weights. Second, the coordination relationship and evolution trend of STI and HQDBI were explored using the coupling coordination model and the Tapio decoupling model. Then, the transfer law and key influencing factors were further investigated using the Markov chain and grey correlation, respectively. The main contribution is the dynamic evolution of the coupling and decoupling relationships from the perspective of multiple Baijiu provinces, and deeply depicts the coordination relationship and evolutionary trends of STI and HQDBI. The results show that: the spatial distribution of the coupling coordination degree shows high values in the east-west and low values in the north-south characteristics. In 2021, a pattern of coordinated development in Baijiu provinces has emerged along the Yangtze River basin. The decoupling state is mainly strong decoupling, but it remains poor in Shanxi. The coordination process is unstable and difficult to achieve leapfrog development. Coordination, sustainability and innovation environment have a greater impact on the coordination of subsystems.

Preparation of layer-assembled W/O/W-type microencapsulated beads and application in solid-state fermentation

In this study, microcapsule beads-0-3-layers (M-0-3 indicates microencapsulated beads with 0, 1, 2, and 3 layers) were prepared, their properties were measured and characterized, and the effects of M-0-3 on solid-state fermentation were investigated. The results showed that in a liquid environment, the releasing glucoamylase activities of M-0-3 were 55.77%, 47.67%, 45.85%, and 42.87% in 360 h, respectively. In the solid environment, the reducing sugar production efficiency of M-0-3 was 29.84%, 27.72%, 19.16%, and 15.93% in 15 days, respectively. Adding M-0-3 improved the alcohol and reduced sugar content while decreasing the residual starch content of the Jiupei, indicating that adding M-0-3 was beneficial to the solid-state fermentation of Baijiu. Solid-state fermentation simulation experiments illustrated that microcapsule beads play a positive role in the production of Baijiu, enhancing raw material utilization and yield of Baijiu production.

Exploring the regulated effects of solid-state fortified Jiuqu and liquid-state fortified agent on Chinese Baijiu brewing

Zaopei is the direct source of Chinese liquor (Baijiu). Adding functional strains to Zaopei is a potential strategy to regulate Baijiu brewing, mainly including the two ways of solid-state fortified Jiuqu (SFJ) and liquid-state fortified agent (LFA). Here, to explore their regulated details, the response patterns of Zaopei microecosystem and the changes in the product features were comprehensively investigated. The results showed that SFJ more positively changed the physicochemical properties of Zaopei and improved its ester content, from 978.57 mg/kg to 1078.63 mg/kg over the fermentation of 30 days, while LFA decreased the content of esters, alcohols, and acids. Microbial analysis revealed that SFJ significantly increased Saccharomycopsis and Aspergillus from the start of fermentation and induced a positive interaction cluster driven by the added functional Paenibacillus, while LFA exhibited a community structure near that of the original microecosystem and led to a simpler network with the reduced microbial nodes and correlations. Metabolism analysis found that both SFJ and LFA weakened the flavor-producing metabolism by suppressing some key enzyme pathways, such as EC 3.2.1.51, EC 4.2.1.47, EC 1.1.1.27, EC 1.1.1.22, EC 1.5.1.10, EC 1.14.11.12. As a result, SFJ improved the raw liquor yield by 28.5 % and endowed the final product with a more fragrant aroma, mainly through ethyl (E)-cinnamate, ethyl isovalerate, ethyl phenacetate with the higher odor activity values, while LFA promoted the yield by 13.2 % and resulted in a purer and less intense aroma through the aroma-active β-damascenone, ethyl heptoate, ethyl phenacetate. These results facilitated the regulated mechanism of SFJ and LFA on Baijiu brewing and indicated that the used functional strains in this study could be applicated in SFJ way for the further industrial-scale application.

Comparison of Aroma Compounds and Sensory Characteristics between Two Different Types of Rice-Based Baijiu

Rice-based Baijiu has gained popularity in the Chinese market. Qingya-flavored Baijiu, a variant of Xiaoqu-fermented Baijiu, employs rice as its primary raw material, with an improved production process compared to traditional rice-flavored Baijiu. We comprehensively characterized and compared the aroma profiles of these two rice-based Baijiu types using static sensory experiments (QDA, quantitative descriptive analysis) and dynamic sensory experiments (TDS, temporal dominance of sensations). Qingya-flavored Baijiu exhibited pronounced plant, oily, and roasted aromas, while traditional rice-flavored Baijiu displayed more prominent fruity, floral, and sour notes. Utilizing GC-O-MS (gas chromatography-olfactometry-mass spectrometry) and multi-method quantification, we qualitatively and quantitatively analyzed 61 key aroma compounds, identifying 22 compounds with significant aroma contributions based on odor activity values (OAVs). Statistical analyses, combining sensory and chemical results, were conducted to predict important aroma compounds responsible for the aroma differences between the two Baijiu types. Aroma Recombination and Omission experiments showed that seven compounds play key roles in the aroma of Qingya-flavored Baijiu, including (2E,4E)-Deca-2,4-dienal, linalool, apricolin, ethyl acetate, ethyl isobutyrate, ethyl caprylate, and ethyl isovalerate.

Preparation of glucoamylase microcapsule beads and application in solid-state fermentation

BACKGROUND

Baijiu brewing adopts the solid-state fermentation method, using starchy raw materials, Jiuqu as saccharifying fermenting agent, and distilled spirits made by digestion, saccharification, fermentation and distillation. In the late stages of solid-state fermentation of Baijiu, the reduced activity of glucoamylase leads to higher residual starch content in the Jiupei, which affects the liquor yield. The direct addition of exogenous glucoamylase leads to problems such as the temperature of the fermentation environment rising too quickly, seriously affecting the growth of microorganisms.

RESULTS

To solve the problem of reduced activity of glucoamylase in the late stage of solid-state fermentation of Baijiu, microcapsule beads (M-B) based on microcapsule emulsion were prepared and the effect of M-B on solid-state fermentation of Baijiu was investigated. The results showed that the release of M-B before and after drying was 53.27% and 25.77% in the liquid state (120 h) and 29.84% and 22.62% in the solid state (15 days), respectively. Adding M-B improved the alcohol by 0.33 %vol and reducing sugar content by 0.51%, reduced the residual starch content by 1.21% of the Jiupei, and had an insignificant effect on the moisture and acidity of the Jiupei.

CONCLUSION

M-B have excellent sustained-release properties. The addition of M-B in solid-state fermentation significantly increased the alcohol content, reduced the residual starch content of Jiupei, ultimately improving the starch utilization rate and liquor yield of Baijiu brewing. The preparation of M-B provides methods and approaches for applying other active substances and microorganisms in the brewing of Baijiu. © 2023 Society of Chemical Industry.

Identification of Chinese baijiu from the same brand based on a graphene quantum dots fluorescence sensing array

The identification of Chinese baijiu is crucial to regulating the international market and maintaining legitimate rights, as the popularity, influence and awareness of baijiu are growing. A graphene quantum dot (GQD) based fluorescence sensor array is designed in this paper. Upon using only GQDs as a single sensing element, combining three different solvents improves the sensing array's detection sensitivity while simplifying material preparation and experimental detection. Adding organic substances creates intermolecular forces between the GQDs and the solvent, causing the fluorescence intensity to change. The sensor array was able to distinguish 21 types of organic matter, different ratios of quaternary mixed organic materials and 17 types of baijiu of the same brand. It also showed excellent performance in the detection of species in blind samples, with the machine learning algorithm successfully distinguishing baijiu from five other distilled spirits. The experiment provides guidance for the practical application of GQDs and provides a simple but effective reference for sensor arrays to detect baijiu.

Integration of Chemometrics and Sensory Metabolomics to Validate Quality Factors of Aged Baijiu (Nianfen Baijiu) with Emphasis on Long-Chain Fatty Acid Ethyl Esters

The storage process of Baijiu is an integral part of its production (the quality undergoes substantial changes during the aging process of Baijiu). As the storage time extends, the flavor compounds in Baijiu tend to undergo coordinated transformation, thereby enhancing the quality of Baijiu. Among them, long-chain fatty acid ethyl esters (LCFAEEs) were widely distributed in Baijiu and have been shown to have potential contributions to the quality of Baijiu. However, the current research on LCFAEEs in Baijiu predominantly focuses on the olfactory sensation aspect, while there is a lack of systematic investigation into their influence on taste and evaluation after drinking Baijiu during the aging process. In light of this, the present study investigates the distribution of LCFAEEs in Baijiu over different years. We have combined modern flavor sensory analysis with multivariate chemometrics to comprehensively and objectively explore the influence of LCFAEEs on Baijiu quality. The results demonstrate a significant positive correlation between the concentration of LCFAEEs and the fruity aroma (p < 0.05, r = 0.755) as well as the aged aroma (p < 0.05, r = 0.833) of Baijiu within a specific range; they can effectively reduce the off-flavors and spicy sensation of Baijiu. Furthermore, additional experiments utilizing a single variable suggest that LCFAEEs were crucial factors influencing the flavor of Baijiu, with Ethyl Palmitate (EP) being the most notable LCFAEE that merits further systematic investigation.

Chinese Baijiu and Whisky: Research Reservoirs for Flavor and Functional Food

Baijiu is a traditional spirit with high reputation in the Chinese community, and whisky, on the other hand, is a renowned spirit in Western culture, with both contributing a major proportion to the consumption and revenue in the global spirit market. Interestingly, starting with similar raw materials, such as grains, diverse production methods lead to different organoleptic profiles. In addition, such enormous attention they attract renders them as a crucial part in food and the related industry. Therefore, great efforts are made in improving product quality and optimizing production processes, such as flavor enhancement, facility development, and deep utilization of byproducts. Given the huge impacts and great involvements of these spirits in the general food industry, research focusing on either spirit is of referential significance for other relevant fields. With the aim of facilitating such collaboration, this review discusses the current research status, in a comparative manner, of both spirits in respect to key production processes-oriented sensory and flavor analysis, deep utilization of byproducts, and spirit-derived functional food investigations. Finally, the internal correlations based on the abovementioned criteria are identified, with research prospects proposed.

The Effects of Ultrasonic and Gamma Irradiation on the Flavor of Potato Wines Investigated by Sensory Omics

Aroma is one of the most fascinating and least-known mysteries of Baijiu research. The volatile compounds (VOCs) of potato wine were evaluated by sensory omics techniques in order to comprehend their overall flavor characteristics and investigate the effects of ultrasonic treatment and gamma irradiation therapy on the aroma of the wine. The findings revealed that a total of 14 flavor compounds were identified by GC-MS. Isoamyl alcohol, ethyl octanoate, and 1,1-diethoxyethane were the key aroma components, according to GC-O analysis. A total of 50 volatile substances were identified by GC-IMS. After being subjected to irradiation and ultrasonic treatment, the alcohol level of the potato wine reduced while the esters content increased. By calculating the relative odor activity value, a total of 29 aroma components were classified as key aroma compounds (ROAV > 1). According to the results of the sensory evaluation-fruity, Fen-flavor, and sweet-and the acceptability of the irradiated and ultrasonicated potato wine were improved. Therefore, the use of ultrasonic and irradiation therapy in potato wine, as well as the overall aroma building of potato wine, can be supported theoretically by this study.

Isolation and Characterization of Yeast with Benzenemethanethiol Synthesis Ability Isolated from Baijiu Daqu

Baijiu, a prevalent alcoholic beverage, boasts over 2000 aroma compounds, with sulfur-containing compounds being the most influential in shaping its flavor. Benzenemethanethiol, a distinctive odorant in baijiu, is known to enhance the holistic flavor profile of baijiu. Despite its importance, there is very little literature on the biotransformation mechanism of benzenemethanethiol. Thus, extensive research efforts have been made to elucidate the formation mechanism of this compound in order to improve baijiu production. In this study, 12 yeast strains capable of generating benzenemethanethiol were isolated from baijiu daqu, and the Saccharomyces cerevisiae strain J14 was selected for further investigation. The fermentation conditions were optimized, and it was found that the optimal conditions for producing benzenemethanethiol were at 28 °C for 24 h with a 4% (v/v) inoculum of 3.025 g/L L-cysteine. This is the first time that yeast has been shown to produce benzenemethanethiol isolated from the baijiu fermentation system. These findings also suggest that benzenemethanethiol can be metabolized by yeast using L-cysteine and benzaldehyde as precursor substrates.

Butyriproducens baijiuensis BJN0003: a potential new member of the family Oscillospiraceae isolated from Chinese Baijiu

Acid-producing bacteria are one kind of crucial species for Baijiu fermentation. The strain BJN0003 with the ability of producing butyric acid was isolated from the cellar mud of Baijiu, and the 16S rRNA gene sequence similarity was 94.2% to its most closely related type species Caproicibacterium lactiferaments JNU-WLY1368T, less than the threshold value of 94.5% for distinguishing genera. Furthermore, the genome of BJN0003 showed a length of 2,458,513 bp and a DNA G + C content of 43.3% through high throughput sequence. BJN0003 exhibited whole-genome average nucleotide identity value of 68.9% to the most closely related species, while the whole-genome digital DNA-DNA hybridization value was only 23.1%, which were both below the delineation thresholds of species. These results indicated BJN0003 could represent a potential novel species of a new genus of the family Oscillospiraceae, and was proposed the name as Butyriproducens baijiuensis. In addition, gene annotation and metabolic analysis showed that BJN0003 harbored the metabolic pathway of converting glucose to butyric acid. The discovery of the new species provided bacterial resource for Baijiu production and the revealing of genetic characteristics would promote the investigation of acid synthesis during Baijiu manufacturing process.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03624-w.

Revelation for the Influence Mechanism of Long-Chain Fatty Acid Ethyl Esters on the Baijiu Quality by Multicomponent Chemometrics Combined with Modern Flavor Sensomics

Long-chain fatty acid ethyl ester (LCFAEEs) is colorless and has a weak wax and cream aroma. It can be used as an intermediate for the synthesis of emulsifiers, and stabilizers and be applied in the production of flavor essence. It is also an important trace component in Baijiu and is attributed to making a contribution to the quality of Baijiu, but its distribution in Baijiu has not been clear, and its influence mechanisms on Baijiu quality have not been systematically studied. Therefore, the distribution of LCFAEEs for Baijiu in different years (2014, 2015, 2018, and 2022), different grades (premium, excellent, and level 1; note: here Baijiu grade classification was based on Chinese standard (GB/T 10781) and enterprise classification standard), and different sun exposure times (0, 6, 12, 20, 30, and 50 days) was uncovered. Thus, in this study, the effect of LCFAEEs on the quality of Baijiu was comprehensively and objectively proven by combining modern flavor sensomics and multicomponent chemometrics. The results showed that with the increase in Baijiu storage time, the concentration of LCFAEEs increased significantly in Baijiu (4.38–196.95 mg/L, p < 0.05). The concentration of LCFAEEs in level 1 Baijiu was significantly higher than that in excellent and premium Baijiu (the concentration ranges of ET, EP, EO, E9, E912, and E91215 were: 0.27–2.31 mg/L, 0.75–47.41 mg/L, 0.93–1.80 mg/L, 0.98–12.87 mg/L, 1.01–27.08 mg/L, and 1.00–1.75 mg/L, respectively, p < 0.05). With the increase in sun exposure time, the concentration of LCFAEEs in the Baijiu first increased significantly and then decreased significantly (4.38–5.95 mg/L, p < 0.05). As the flavor sensomics showed, the concentrations of LCFAEEs in Baijiu bodies were significantly correlated with the Baijiu taste sense (inlet taste, aroma sensation in the mouth), as well as with the evaluation after drinking (maintaining taste) (p < 0.05, r > 0.7). Based on the above, LCFAEEs are critical factors for Baijiu flavor thus, it is essential to explore a suitable concentration of LCFAEEs in Baijiu to make Baijiu’s quality more ideal.

Comparison of the Aroma-Active Compounds and Sensory Characteristics of Different Grades of Light-Flavor Baijiu

This study comprehensively characterized and compared the aroma differences between four different grades of Fenjiu (FJ, the most representative light-flavor Baijiu). Aroma-active compounds were analyzed by liquid-liquid extraction (LLE) coupled with gas chromatography-olfactometry-mass spectrometry (GC-O-MS). A total of 88 aroma-active compounds were identified, and 70 of them were quantified. The results showed that a majority of aroma compounds in high-grade FJ had higher aroma intensities and concentrations. Among these compounds, there were 28 compounds with odor activity values (OAVs) greater than one in all four wines, which indicated that they might contribute to the characteristic aroma of FJ. Temporal dominance of sensation (TDS) and quantitative descriptive analysis (QDA) were used to characterize the sensory differences. The results suggested that high-grade FJ had a rich, pleasant and lasting retronasal aroma perception and exhibited pleasant orthonasal aroma of floral, fruity, sweet and grassy. Partial least squares regression (PLSR) analysis effectively distinguished four kinds of FJ and revealed associations between the orthonasal aroma attributes and the aroma compounds with OAVs >1. There were 15 compounds with variable importance in projection (VIP) values >1, and they were considered potential aroma markers for quality prediction.

Investigation of Solid Phase Microextraction Gas Chromatography–Mass Spectrometry, Fourier Transform Infrared Spectroscopy and 1H qNMR Spectroscopy as Potential Methods for the Authentication of Baijiu Spirits

The baijiu spirit is often the focus of fraudulent activity due to the widely varying prices of the products. In this work, Solid Phase Microextraction Gas Chromatography (SPME GCMS), Fourier Transform Infrared (FTIR) Spectroscopy and 1H qNMR spectroscopy were evaluated as potential methods to authenticate baijiu samples. Data were collected for 30 baijiu samples produced by seven different distilleries. The data from the SPME GCMS and FTIR methods were treated by a Principal Component Analysis to identify clusters that would suggest chemical differences in the products from different distilleries. The results suggest that SPME GCMS has the potential to be a fully portable method for baijiu authentication. FTIR did not appear suitable for authentication but can be used to find the %ABV range of the sample. 1H quantitative NMR (1H qNMR) was utilized to quantify the ethanol concentrations and calculate the observable congener chemistry comprising ester, ethanol, methanol, fusel alcohol, and organic acids. Discrepancies in ethanol content were observed in three samples, and a lack of major congeners in two samples indicates the possible presence of a counterfeit product. Detailed and quantitative congener chemistry is obtainable by NMR and provides a possible fingerprint analysis for the authentication and quality control of baijiu style, producer, and the length of the ageing process.

A Thermodynamic and Kinetic Study on Electrochemical Esterification in Aroma-Enhanced Distilled Liquor (Baijiu)

The development of low-alcohol Baijiu is consistent with demand for the industry’s sustainable development. However, the ester aroma of low-alcohol Baijiu is insipid and unstable—mainly due to the hydrolysis of esters during shelf life—thus reducing the industry scale of low-alcohol Baijiu to a significantly small range. An electrochemical method for improving low-alcohol Baijiu’s ester concentration and stability was investigated from the aspects of thermodynamics and kinetics. The key finding is that the new Baijiu’s ester content obtained through distillation is relatively high, exceeding its content in the thermodynamic equilibrium state. Thus, the ester will be hydrolyzed during shelf life. The idea of applying electrochemical catalytic esterification technology to the production of low-alcohol Baijiu in this study is directly derived from the production practice of Baijiu factories; it provides a direction for the further optimization of low-alcohol Baijiu to facilitate the production of an alternative product that will contribute to public health.