Untargeted Headspace-Gas Chromatography-Ion Mobility Spectrometry in Combination with Chemometrics for Detecting the Age of Chinese Liquor (Baijiu)

Aroma Release and Consumer Perception During Cider Consumption

Flavor is an important property affecting consumer acceptance, yet little is known about the correlation between the sensory attributes, volatile compounds, and consumer preference during cider consumption. This study was the first to evaluate which sensory attributes of commercial apple ciders in China were preferred by Chinese consumers. Meanwhile, GC-MS and GC-IMS were conducted to characterize the aroma release both in orthonasal and retronasal olfactory perceptions. The sensory analyses exhibited that Chinese consumers preferred "sweet cider", and sensory attributes such as "a-tropical fruit", "f-fruity" and "t-sweet" were the most popular. A total of 63 volatile compounds were identified using GC-MS, while both the variety and concentrations of these compounds detected by GC-IMS were lower. Finally, partial least squares (PLS) analysis was used to establish two models based on sensory data, and orthonasal and retronasal volatile compounds. The two models had 32 and 29 compounds with variable importance in projection (VIP) values > 1, respectively. The results revealed that the compounds with high correlation with "t-sweet" and "f-fruity" were roughly the same in two PLS models, whereas the number of compounds contributing positively to "t-sour" and "f-fermented" changed significantly.

Advancing Stable Isotope Analysis for Alcoholic Beverages' Authenticity: Novel Approaches in Fraud Detection and Traceability

BACKGROUND

Alcoholic beverages have been popular for thousands of years due to their unique flavors and cultural significance. However, the industry's high profit margins have led to increasingly sophisticated counterfeiting practices. Stable isotope analysis has emerged as one of the most promising techniques for addressing authenticity and traceability challenges in alcoholic beverages. Scope and approach: This review presents a comprehensive summary of the principles and recent advancements in the application of stable isotope techniques for authenticity assessment. It examines their use in detecting fraud (e.g., identifying edible alcohol, exogenous water, carbonylation, and trace compounds), vintage identification, and geographical origin determination across various alcoholic beverages, with a particular focus on wine, Chinese baijiu, and beer.

CONCLUSIONS

Stable isotope analysis is a powerful tool for verifying the authenticity of alcoholic beverages, offering effective solutions to combat counterfeiting, mislabeling, and adulteration. Future studies should focus on understanding the ecological, biological, and hydrometeorological factors influencing isotope signatures and develop advanced multi-isotope and chemometric approaches to improve reliability. Expanding global databases and integrating emerging technologies such as artificial intelligence (AI) and machine learning will further enhance the effectiveness and accessibility of stable isotope techniques, ensuring safer and higher-quality alcoholic beverages for consumers worldwide.

Evolution of aroma compounds in round soy sauce aroma type baijiu during aging and the effect of aging markers on the lasting aroma in finished glass

Soy sauce aroma type Baijiu (SSAB) is a complex blend of seven rounds of raw SSAB, each with distinct aroma profiles that evolve during maturation. Tracking the aging of individual rounds is crucial for understanding flavor development. The round 1-4 SSABs were analyzed by gas chromatography-mass spectrometry and an electronic tongue over one-year aging. Results showed that short/medium-chain esters decrease while long-chain esters, acids, aldehydes, pyrazines, ketones, and furans increase. Kinetic analysis showed that short/medium-chain ethyl esters reach equilibrium in the esterification-hydrolysis reactions, whereas long-chain ethyl esters favor esterification, with their reaction quotient (Qc) diverging from the equilibrium point. Linoleic acid ethyl ester, identified as a key aging marker, was found to reduce the volatilization rate of critical aroma compounds in the finished glass, thereby prolonged the duration of lingering aromas. These findings provide a foundation for improving SSAB blending and storage, highlighting aging's key role in enhancing Baijiu quality.

A two-step framework integrating lasso and Relaxed Lasso for resolving multidimensional collinearity in Chinese baijiu aging research

The aging process is crucial for Chinese Baijiu production, significantly enhancing the spirit's flavor, aroma and quality. However, aging involves a complex interplay of numerous compounds, and the extensive duration required for aging leads to a scarcity of samples available for scientific research. These limitations pose a challenge in analyzing high-dimensional data with collinearity, complicating the understanding of the intricate chemical processes at play. In this article, a two-step framework was proposed that integrated Relaxed Lasso regression models with Lasso-selected predictors to address this issue. Baijiu samples subjected to various aging conditions were analyzed using direct GC-MS and HS-GC-MS, and the obtained data was processed by this approach. The results demonstrate significantly superior performance compared to other methods, including PLSR and Gradient Boosting. Analyses were also performed on a previously documented dataset, yielding enhanced results and underscoring the method's advantage in processing high dimensional data with multicollinearity. Moreover, this method proved effective in screening of potential indicative compounds, highlighting its utility in Baijiu aging research.

Chemical Composition and Flavor Characteristics of Cider Fermented with Saccharomyces cerevisiae and Non-Saccharomyces cerevisiae

Cider flavor has a very important impact on the quality. Solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) combined with gas chromatography-ion mobility spectrometry (GC-IMS) tested different kinds of non-Saccharomyces yeasts and Saccharomyces cerevisiae (S. cerevisiae) co-inoculated for the fermentation of cider to determine differences in aroma material, and the determination of odor activity value (OAV) is applied less frequently in research. Through Rhodotorula mucilaginosa, Debaryomyces hansenii, Zygosaccharomyces bailii, and Kluyveromyces Marxianus, four different strains of non-Saccharomyces yeast fermented cider, and it was found that, in both the chemical composition and flavor of material things, compared with monoculture-fermented cider using S. cerevisiae, all differences were significant. Co-inoculated fermentation significantly improved the flavor and taste of cider. As in the volatile compounds of OVA > 1, octanoic acid (Sc 633.88 μg/L, co-inoculation fermented group 955.49 μg/L) provides vegetable cheese fragrance and decanoic acid, ethyl ester (Sc 683.19 μg/L, co-inoculation fermented group 694.98 μg/L) a creamy fruity fragrance, etc., and the average content increased after co-inoculated fermentation. Phenylethyl alcohol, which can produce a rose scent, was relatively abundant in cider samples and varied greatly among the groups. Moreover, the contents of ethyl lactate and 1-butanol in the Sc+Rm (ciders fermented by S. cerevisiae and R. mucilaginosa) were the highest of all of the cider samples. Different types of non-Saccharomyces yeast produced cider with different flavor characteristics. This study demonstrates that different species of non-Saccharomyces yeast do have an important impact on the characteristics of cider and that co-inoculation with non-Saccharomyces yeast and S. cerevisiae for cider fermentation may be a strategy to improve the flavor of cider.

Application of GC-IMS coupled with chemometric analysis for the classification and authentication of geographical indication agricultural products and food

Geographical indications (GI) are used to protect the brand value of agricultural products, foodstuffs, and wine and promote the sustainable development of the agricultural and food industries. Despite the necessity for the traceability and recognition of GI product characteristics, no rapid, non-destructive approaches currently exist to identify, classify, and predict these properties. The application of gas chromatography-ion mobility spectrometry (GC-IMS) has increased exponentially due to instrument robustness and simplicity. This paper provided a detailed overview of recent GC-IMS applications in China for the quality evaluation of GI products and food, including agricultural products, as well as traditional Chinese food and liquor. The general workflow of GC-IMS coupled with chemometric analysis is presented, including sample collection, model construction and interpretation, and data acquisition, processing, and fusion. Several conclusions are drawn to increase partial least squares-discriminant analysis (PLS-DA) model precision, a chemometric technique frequently combined with GC-IMS.

Machine learning based age-authentication assisted by chemo-kinetics: Case study of strong-flavor Chinese Baijiu

The aged Chinese liquor, Baijiu, is highly valued for its superior organoleptic qualities. However, since age-authentication method and aging-mechanism elucidation of Baijiu is still in the exploratory stage, high-quality aged Baijiu is often replaced by lower-quality, less-aged product with fraudulent mislabeling. Authentic high-quality strong-flavor Baijiu was analyzed by gas chromatography-mass spectrometry. Total esters decreased with aging, while acids, alcohols, aldehydes, ketones, terpenes, pyrazines increased. Although concentrations of partial compounds showed non-monotonic profiling during aging, a close positive linear correlation (R² = 0.7012) of Baijiu Evenness index (0.55-0.59) with aging time was observed, indicating a more balanced composition in aged Baijiu. The reaction quotient (Qc) of each esterification, calculated by the corresponding reactant and product concentration, approached to the corresponding thermodynamic equilibrium constant Kc. This result demonstrated that the spontaneous transformation driven by thermodynamics explained part of the aging compositional profiling. Furthermore, an aging-related feature selection and an age-authentication method were established based on three models combined with five ranking algorithms. Forty-one key features, including thirty-six compound concentrations, four esterification Qc values and the Evenness index were selected out. The age-authentication based on neural network using forty-one input features accurately predicted the age group of Baijiu samples (F1 = 100 %). These findings have deepened understanding of the Baijiu aging mechanism and provided a novel, effective approach for age-authentication of Baijiu and other liquors.

FT-IR combined with chemometrics in the quality evaluation of Nongxiangxing baijiu

Recently, there has been an increasing demand for developing a reliable method to assess the quality of liquor in the baijiu industry quickly and accurately. The present study sought to establish a strategy for rapid quantitative analysis of the primary flavor components in Nongxiangxing baijiu. Under the experimental conditions, 7 of the 10 major flavor components in Nongxiangxing baijiu could be quantified effectively, such as ethyl butyrate (R²p = 0.9942), ethyl lactate (R²p = 0.9438), n-butanol (R²p = 0.9048), isobutanol (R²p = 0.9696), acetic acid (R²p = 0.9600), butyric acid (R²p = 0.8448), caproic acid (R²p = 0.9971). This result indicates that FT-IR combined with quantitative chemometric modeling could be a potential approach for rapid quality assessment of Nongxiangxing baijiu. Overall, this study provides a theoretical basis for subsequent related studies on Nongxiangxing baijiu.

Synergy of physicochemical reactions occurred during aging for harmonizing and improving flavor

Numerous counterfeit vintage Baijiu are widely distributed in the market driven by economic interest which disturb the market economic rules and damage the reputation of particular Baijiu brand. Found on the situation, the Baijiu system variation during aging period, aging mechanisms and discrimination strategies for vintage Baijiu are systematically illuminated. The aging mechanisms of Baijiu cover volatilization, oxidation, association, esterification, hydrolysis, formation of colloid molecules and catalysis by metal elements or other raw materials dissolved from storage vessels. The discrimination of aged Baijiu has been performed by electrochemical method, colorimetric sensor array or component characterization coupled with multivariate analysis. Nevertheless, the characterization of non-volatile compounds in aged Baijiu is deficient. Further research on the aging principles, more easy-operation and low-cost discrimination strategies for aged Baijiu are imperative. The above information is favorable to better understand the aging process and mechanisms of Baijiu, and promote the development of artificial aging techniques.