Characterization of volatile organic compounds in wild thyme (Thymus serpyllum L.) from central and northern China based on comprehensive GC × GC-TOFMS and chemometrics

To optimize the compatibility with target ingredients in food processing and ensure standardized application, it is essential to characterize thyme's volatile organic compounds (VOCs) from specific species and origins. In this study, 116 VOCs were identified in thyme samples from four main Chinese production regions by two-dimensional gas chromatography/time-of-flight mass spectrometry (GC × GC-TOFMS). Among them, eight compounds- thymol (5.27 %-13.28 %), eucalyptol (9.25-12.23 %), thymoquinone (11.16-15.98 %), etc.- were identified as the most abundant constituents. Samples NX, WQ, JB, and NM were classified into different chemotypes: thymol/eucalyptol/thymoquinone/<i>p</i>-cymene, thymoquinone/eucalyptol/thymol, thymoquinone/eucalyptol/<i>p</i>-cymene, and thymoquinone/carvacrol/isoborneol, respectively. Forty odor-active compounds were determined through relative odor activity value (ROAV) analysis. Furthermore, the variable importance in projection (VIP) method was applied to identify 14 and 5 VOCs as potential markers for thyme volatility and odor activity, respectively. These findings provide a valuable reference for expanding the application of Chinese thyme as a culinary herb in the food processing industry.