Identification of regionalmarkers based on the flavor molecular matrix analysis of sauce-aroma style baijiu.

BACKGROUND: Baijiu is a very complex system and its flavor substances are endogenous, influenced by raw materials, starter, production process, production region and other factors. The production region directly affects the composition of flavor substances and quality of baijiu. However, identification of baijiu region is challenging because the corresponding relationship between the production region and baijiu quality is not clear, and the identification of regionalmarkers is indeterminate. In this study, the differences in volatile components of sauce-aroma style baijiu from four representative regions were investigated. RESULTS: A total of 94 volatile compounds were identified in samples tested. Additionally, it was verified that 35 potential flavor substances had important contributions to the aroma of sauce-aroma style baijiu. Meanwhile, nine potential regionalmarkers were screened through multivariate analysis. Further, based on distribution of volatile compounds and the results of sensory evaluation combined with multivariate analysis, a molecular matrix and correlation network were established according to the results of addition experiments, which showed that six substances had a significant impact on the flavor of the tested samples. CONCLUSION: Six key flavor substances (ethyl octanoate, ethyl 2-methylpropanoate, propyl acetate, ethyl heptanoate, 2-nonanone and butyl hexanoate) were considered as important regionalmarkers to effectively identify the production region of sauce-aroma style baijiu. © 2023 Society of Chemical Industry.

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.

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.

Uncover the Flavor Code of Roasted Sesame for Sesame Flavor Baijiu: Advance on the Revelation of Aroma Compounds in Sesame Flavor Baijiu by Means of Modern Separation Technology and Molecular Sensory Evaluation.

Baijiu occupies an important position in the food industry of China and is deeply recognized as the national liquor of China. According to the flavor characteristics, Baijiu is artificially divided into 12 categories. The sesame flavor of Baijiu was accidentally discovered after the founding of the People's Republic of China. Sesame flavor Baijiu is known for its special aroma of roasted sesame, which attracts people's attention. Modern flavor extraction, separation technology, and flavor analysis technology, greatly promote the identification and evaluation of trace components and aroma compounds in Baijiu. Of note, it has successfully identified which aroma compounds are responsible for the special roasted sesame aroma in sesame flavor Baijiu. On this basis, this paper summarizes the extraction methods, detection techniques, analysis methods, aroma expression, and sensory evaluation methods that have been applied for the verification and evaluation of trace components and aroma compounds in Baijiu. More specifically, the research progress on the revelation of aroma compounds in sesame flavor Baijiu is systematically summarized. Next, people will focus on the changing mechanisms of aroma compounds and the metabolic regulation in Baijiu during brewing, which will be helpful for industrialization and the modern production of Baijiu.

"Key Factor" for Baijiu Quality: Research Progress on Acid Substances in Baijiu.

Baijiu is the national liquor of China, which has lasted in China for more than 2000 years. Abundant raw materials, multi-strain co-fermentation, and complex processes make the secrets of baijiu flavor and taste still not fully explored. Acid substances not only have a great influence on the flavor and taste of baijiu, but also have certain functions. Therefore, this paper provides a systematic review for the reported acid substances, especially for their contribution to the flavor and functional quality of baijiu. Based on previous studies, this paper puts forward a conjecture, a suggestion, and a point of view, namely: the conjecture of "whether acid substances can be used as 'key factor' for baijiu quality "; the suggestion of "the focus of research on acid substances in baijiu should be transferred to evaluating their contribution to the taste of baijiu"; and the view of "acid substances are 'regulators' in the fermentation process of baijiu". It is worth thinking about whether acid substances can be used as the key factors of baijiu to be studied and confirmed by practice in the future. It is hoped that the systematic review of acid substances in baijiu in this paper can contribute to further in-depth and systematic research on baijiu by researchers in the future.

Unraveling variation on the profile aroma compounds of strong aroma type of Baijiu in different regions by molecular matrix analysis and olfactory analysis.

Among 12 aroma types of Baijiu, the strong aroma type of Baijiu (Nongxiangxing Baijiu) is well received by customers for its rich and full aroma profile. According to the aroma characteristics of different geographical locations, Nongxiangxing Baijiu can be divided into Jianghuai, Sichuan and North categories. However, the reasons for the differences in Nongxiangxing Baijiu flavor in different regions are still unclear. Hence, representative brands (i.e., Gujinggong, Luzhou Laojiao and Banchengshaoguo) of Nongxiangxing Baijiu from three representative regions were chosen to explore their differences in profile aroma compounds. In this study, a total of 50, 41, 35 potential aroma compounds in Banchengshaoguo, Gujinggong, and Luzhou Laojiao samples were respectively identified by direct injection combined with gas chromatography-olfactometry/mass spectrometry (GC-O/MS). Among them, 18 aroma compounds were further recognized as important aroma compounds owing to their high flavor dilution (FD) value, Osme value, and odor activity value (OAV) ≥ 1. Moreover, the relationship between the above potential aroma compounds and the aroma profile of the three representative samples was analyzed by molecular matrix analysis. The results showed that various aroma compounds contributed differently to the flavor characteristics of Nongxiangxing Baijiu. In particular, 13 aroma compounds were tentatively defined as crucial profile aroma compounds due to their high aroma expression intensity and remarkable contribution to the flavor characteristics of Nongxiangxing Baijiu in different regions, and these crucial profile aroma compounds may be the reason for the difference in aroma profile of Nongxiangxing Baijiu from distinct regions.

Correction: Unraveling variation on the profile aroma compounds of strong aroma type of Baijiu in different regions by molecular matrix analysis and olfactory analysis.

[This corrects the article DOI: 10.1039/D1RA06073B.].