###### Abstract  
Distilled liquors are important products, both culturally and economically. Chemically, as a complex mixture, distilled liquor comprises various chemical compounds in addition to ethanol. However, the chemical components of distilled liquors are still insufficiently understood and compositional differences and similarities of distilled liquors from different cultures have never been compared. For the first time, both volatile organic compounds (VOCs) and non-VOCs in distilled liquors were profiled using mass spectrometry-based metabolomic approaches. A total of 879 VOCs and 268 non-VOCs were detected in 24 distilled liquors including six typical Chinese baijiu and 18 typical Western liquors. Principal component analysis and a correlation network revealed important insights into the compositional differences and similarities of the distilled liquors that were assessed. Ethyl esters, a few benzene derivatives, and alcohols were shared by most distilled liquors assessed, suggesting their important contribution to the common flavor and mouthfeel of distilled liquors. Sugars and esters formed by fatty alcohol differ significantly between the assessed Chinese baijiu and Western liquors, and are potential marker compounds that could be used for their discrimination. Factors contributing to the differences in chemical composition are proposed. Our results improve our understanding of the chemical components of distilled liquors, which may contribute to more rigorous quality control of alcoholic beverages. distilled liquor; metabolomics; volatile compounds; HS-SPME-GC-TOFMS; non-volatile compounds; GC-TOFMS +
Footnote †: journal: Medical  
and baijiu [8]. However, the chemical components of distilled liquors are still poorly understood, because non-VOCs, which often influence the overall flavor volatility and perception, also exist in distilled liquors [9]. For instance, we recently detected lichenysin (a macro-molecular cyclic lipopeptide) in baijiu [9; 10], and caramel is often manually added into aged whisky and brandy [2; 11]. The chemical compounds in distilled liquors from different cultures may vary given the use of different raw materials, production processes, and the maturation conditions. For example, most Western liquors are fermented by yeasts, which significantly differs from baijiu, whose fermentation is driven by various microorganisms (bacteria, yeasts, and filamentous fungi) [3]. In addition, baijiu is produced through solid-state fermentation and distillation, whereas Western liquors are produced by submerged fermentation and distillation. Hence, it is reasonable to deduce that the composition of Chinese baijiu and Western liquor is different. However, to the best of our knowledge, these compositional differences and similarities have never been compared. Metabolomics, as a holistic and powerful approach, may be suitable for analyzing the complete chemical composition of distilled liquors. Metabolomics focuses on the comprehensive measurement of large-scale small molecular metabolites in complex biological and abiotic samples and is the third most commonly employed omics technology, after genomics and proteomics [12; 13]. Powered by the unparalleled sensitivity and specificity, high resolution and wide dynamic range of MS [14], automated sample processing, and advanced metabolomic protocols, high-throughput GC-MS is a reliable tool for chemical profiling, and has been extensively applied in the analyses of components from foods and beverages [15; 16]. Thus, metabolomics is ideally positioned for the metabolite profiling of distilled liquors. We could also establish more rigorous quality control of distilled liquors through metabolomics. For example, Chinese baijiu is produced through mixed culture fermentation, solid-state fermentation, and simultaneous saccharification and fermentation. The nature of Chinese baijiu production makes it susceptible to environmental factors.