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Pooled samples for each type of vinegar by combining 1 mL of each product were prepared to evaluate the metabolomic differences among the three types of vinegar. For metabolite extraction, 450 µL of methanol containing internal standards (2-chloro-L-phenylalanine, 1 mg/mL in water) was added to 50 µL of each sample or pooled samples, and then the mixture was vortexed and sonicated for 5 min. The extracted solution was filtered and dried using 0.2 μm polytetrafluoroethylene (PTFE) syringe filters (Chromdisc, Daegu, Republic of Korea) and a speed vacuum concentrator (Biotron, Seoul, Republic of Korea), respectively. The dried extracts were re-dissolved in methanol to make 5 mg/mL solution.

An ultrahigh-performance liquid chromatography (UHPLC) system consisting of a Vanquish binary pump C system coupled with a Vanquish™ Split Sampler CT (Thermo Fisher Scientific, Bremen, Germany) was used for chromatographic separation. Mass spectrometric detection was performed using an Orbitrap Exploris™ 120 system (Thermo Fisher Scientific). Chromatographic separation was achieved using an ACQUITY UPLC HSS T3 column (100 Å, 1.8 µm, 2.1 mm × 100 mm; Waters Corp., Milford, MA, USA). The injection volume was 5 μL.

To obtain MS spectral data, UHPLC–ESI–MS/MS analyses of liquid extracts were performed using an Orbitrap Exploris™ 120 mass spectrometer (Thermo Fisher Scientific, Germany) coupled with a Vanquish binary pump C UHPLC system and a Vanquish™ Split Sampler CT autosampler. Mass spectra were acquired over an m/z range of 100–1500. All analyses were performed in triplicate in random order to minimize analytical bias.