Characterization of Aroma and Non-Volatile Profiles of Chinese Dark Soy Sauce Using HS-SPME-GC-MS, GC-IMS, and HPLC-MS During Preparation Process

Flavor is the core quality attribute of dark soy sauce, which undergoes complex chemical transformations during blending, heat holding, concentration and sun exposure. In this study, three complementary analytical techniques including headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS-SPME-GC-MS), gas chromatography–ion mobility spectrometry (GC-IMS) and high-performance liquid chromatography–mass spectrometry (HPLC-MS) were integrated to perform an exploratory compositional profiling for the dynamic variations in volatile organic compounds (VOCs) and non-volatile compounds (NVCs) throughout dark soy sauce preparation using samples from one continuous industrial production run. In total, 187 VOCs were tentatively identified by HS-SPME-GC-MS (categorized into Metabolomics Standards Initiative (MSI) Levels 2 and 3) and 91 signals by GC-IMS (distinguishing between monomer and dimer peaks), and 1199 NVCs were characterized via HPLC-MS. Although the compound categories remained consistent across all stages, their relative abundances exhibited obvious dynamic differences. High-temperature holding yielded opposite variation trends between volatile and non-volatile heterocyclic compounds. The concentration step promoted the accumulation of non-volatile lipids as well as volatile aldehydes, heterocycles and benzenoids, accompanied by a sharp loss of acids and alcohols. During sun exposure, volatile aldehydes and benzenoids increased while furans decreased, and non-volatile components remained relatively stable. Combined with the observed metabolite variation patterns, the joint effects of the Maillard reaction, caramelization and photo-oxidation can well interpret the above-mentioned changes in flavor-related substances. This exploratory dataset provides useful references for process optimization and flavor regulation of brewed dark soy sauce.