Characterization of Odor-active Compounds in Sweet-type Chinese Rice Wine by Aroma Extract Dilution Analysis with Special Emphasis on Sotolon

The aroma characteristics of sweet-type Chinese rice wine were studied by sensory analysis, aroma extract dilution analysis (AEDA), and quantitative analysis. Sensory evaluation demonstrated that a caramel-like note was the most distinctive characteristic for sweet-type Chinese rice wine. AEDA was carried out on the extract of a typical sweet-type Chinese rice wine sample. Thirty-nine odor-active regions were detected in the sample with a flavor dilution (FD) factor ≥8, and 37 of these were further identified. Among them, sotolon and 2- and 3-methylbutanol showed the highest FD factor of 1024, followed by 2-acetyl-1-pyrroline (tentatively identified), dimethyl trisulfide, 2-phenylethanol, and vanillin with a FD factor of 512. Sotolon was identified as a key aroma compound in Chinese rice wine for the first time. AEDA results indicated that sotolon (caramel-like/seasoning-like) was the potentially key contributor to the caramel-like descriptor of sweet-type Chinese rice wine. The concentration of sotolon in Chinese rice wine was further quantitated by Lichrolut-EN solid-phase extraction coupled with microvial insert large volume injection method. The content of sotolon ranged from 35.93 to 526.17 μg/L, which was above its odor threshold (9 μg/L) for all Chinese rice wine samples. The highest concentration of sotolon was found in the sweet-type Chinese rice wine, which highlighted the important aroma role of sotolon for this particular type of Chinese rice wine.