Characterization of Volatile Aging Markers in Traditional Semi-Dry Huangjiu by Comprehensive Two-Dimensional Gas Chromatography-Time of Flight Mass Spectrometry and Chemometrics

In this investigation, headspace solid-phase microextraction (HS-SPME) coupled with comprehensive two-dimensional gas chromatography-time of flight mass spectrometry (GC × GC-TOFMS) was used to analyze the volatile compounds of traditional semi-dry Huangjiu (Chinese yellow rice wine) of different ages. Furthermore, chemometrics was used to identify the aging markers. The results showed that a total of 351 compounds were identified in Huangjiu of six ages, of which 40 compounds were found in Huangjiu for the first time. The total number of volatile compounds showed an increasing trend with aging time. One-way analysis of variance (ANOVA) and correlation analysis found a strong correlation between the contents of 107 compounds that significantly changed and aging time, among which 55 compounds such as 2-acetylthiophene were found to be significantly correlated with aging time for the first time. Principal component analysis (PCA) and cluster analysis revealed that the aging process of traditional semi-dry Huangjiu could be divided into three stages: short-term aging (1–3 years), medium-term aging (6–12 years) and long-term aging (more than 15 years). By partial least squares-discriminant analysis (PLS-DA), 37 aging markers were selected, the contents of 12 compounds of which decreased significantly while the other 25 increased significantly during the aging process. Ten most representative key aging markers were finally identified based on Pearson correlation coefficients, among which 5 compounds including isoamyl butanoate, butanoic acid, 2-furanmethanol, 2-acetyl-5-methylfuran and o-cresol were defined as key aging markers of Huangjiu for the first time. This study provides a scientific basis for understanding the aging process, evaluating the quality and identifying the age of Huangjiu.