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. 2022 Oct 3:9:1022600.
doi: 10.3389/fnut.2022.1022600. eCollection 2022.

Characterization of volatile thiols in Chinese liquor (Baijiu) by ultraperformance liquid chromatography-mass spectrometry and ultraperformance liquid chromatography-quadrupole-time-of-flight mass spectrometry

Yan Yan  1   2 , Jun Lu  3 , Yao Nie  2 , Changwen Li  3 , Shuang Chen  2 , Yan Xu  2
Affiliations

Characterization of volatile thiols in Chinese liquor (Baijiu) by ultraperformance liquid chromatography-mass spectrometry and ultraperformance liquid chromatography-quadrupole-time-of-flight mass spectrometry

Yan Yan et al. Front Nutr. .

Abstract

Volatile thiols give a unique flavor to foods and they have been extensively studied due to their effects on sensory properties. The analytical assay of volatile thiols in food is hindered by the complexity of the matrix, and by both their high reactivity and their typically low concentrations. A new ultraperformance liquid chromatography (UPLC) strategy has been developed for the identification and quantification of volatile thiols in Chinese liquor (Baijiu). 4,4'-Dithiodipyridine reacted rapidly with eight known thiols to form derivatives, which provided a diagnostic fragment ion (m/z 143.5) for tandem mass spectrometry (MS/MS). To screen for new thiols, Baijiu samples were analyzed by means of UPLC-MS/MS screening for compounds exhibiting the diagnostic fragment ion (m/z X→143.5). New peaks with precursor ions of m/z 244, 200 and 214 were detected. Using UPLC with quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF-MS) and authentic standards, ethyl 2-mercaptoacetate, 1-butanethiol, and 1-pentanethiol were identified in Baijiu for the first time. Commercial Baijiu samples were analyzed with the new method and the distribution of 11 thiols was revealed in different Baijiu aroma-types. The aroma contribution of these thiols was evaluated by their odoractivity values (OAVs), with the result that 7 of 11 volatile thiols had OAVs > 1. In particular, methanethiol, 2-furfurylthiol, and 2-methyl-3-furanthiol had relatively high OAVs, indicating that they contribute significantly to the aroma profile of Baijiu.

Keywords: Baijiu; UPLC-MS/MS; odor activity value; quantification; thiols.

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Conflict of interest statement

Author JL and CL were employed by Guizhou Guotai Liquor Group Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
Mass spectrometry (MS/MS) spectrum of the derivatized thiols (A). Multiple-reaction-monitoring (MRM) analysis of the derivatized thiol standards (1–8) in positive mode by ultraperformance liquid chromatography (UPLC)–mass spectrometry (MS/MS) (B).
FIGURE 2
FIGURE 2
Analysis of the derivatized Baijiu sample using precursor mode and ultraperformance liquid chromatography (UPLC)–mass spectrometry (MS/MS) screening for compounds releasing a disulfanylpyridin ion (m/z X→143.5) (A). MS spectra of the three unknown peaks by UPLC–MS/MS (B–D). MS peaks observed at 5.06 (unknown #1), 10.83 (unknown #2), and 16.46 min (unknown #3) using ultraperformance liquid chromatography quadrupole-time-of-flight mass spectrometry (UPLC–Q-TOF–MS) and their corresponding elemental composition (E–G).
FIGURE 3
FIGURE 3
Principal component analysis (PCA) of the thiols in four aroma-types Baijiu samples (A). Heat map of thiols (B). The histogram shows the value of variable importance for projection (VIP) (C).
See this image and copyright information in PMC

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