Distribution and sensory characteristic of ethyl 2-hydroxy-3-methylbutyrate enantiomers in different flavor types Baijiu

In this study, the ethyl 2-hydroxy-3-methylbutyrate (E2H3MB) in Baijiu was analyzed by liquid-liquid extraction (LLE) combined with gas chromatography (GC) and Chiral gas chromatography-mass spectrometry (Chiral-GC-MS), the gas chromatography analysis conditions were optimized, and the enantiomeric distribution of E2H3MB in 12 flavor types Baijiu was investigated. The olfactory threshold and sensory characteristics of the E2H3MB enantiomer in water and volume fraction 46% ethanol solution were evaluated by three-alternative forced-choice (3-AFC) threshold determination method. The results showed that the CYCLOSIL-B chromatography column (30 m×0.25 mm×0.25 μm) had a good separation effect on E2H3MB. When the heating rate was 1.5 ℃/min and the carrier gas flow rate was 1.0 ml/min, the separation of E2H3MB enantiomer was the optimal, and the separation degree (R)=5.0＞1.5. Except for rice-flavor, light-flavor (Qingxiangxing) and Chi-flavor Baijiu, only (R)-configuration E2H3MB ((R)-E2H3MB) was detected in other types of Baijiu, and there were significant differences in the (R)-E2H3MB contents in the same type of Baijiu (P＜0.05). The results of sensory characteristics results indicated that in water and volume fraction 46% ethanol solution, the olfactory threshold of (R)-E2H3MB was approximately 2.1 times that of (S)-configuration E2H3MB ((S)-E2H3MB) ((R)-configuration 38 μg/L); (S)-configuration 18 μg/L, and about 1.9 times ((R)-configuration 322 mg/L; (S)-configuration 173 mg/L), both configurations exhibited pleasant sweet and fruity aromas. The research results were conducive to the refinement of Baijiu flavor wheel, providing a reference basis for studying the distribution of enantiomers of chiral flavor substances in Baijiu and enriching people’s understanding of chiral flavor substances in Baijiu.