Aroma characteristics of 'Yeniang No.2' (Vitis heyneana var. adenoclada) wine produced by two-crop-a-year cultivation system

In this study, the wine was prepared using 'Yeniang No.2' grapes cultivated under a Two-crop-a-year overlapping generations cultivation system as raw material. The physicochemical indicators of raw materials and wine were detected by conventional detection methods. The volatile flavor substances of wine were detected by headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS), and the aroma characteristics were evaluated by orthogonal partial least squares discriminant analysis (OPLS-DA) combined with odor activity value (OAV). The results demonstrated that compared to the first-crop grapes, the second-crop 'Yeniang No.2' grapes exhibited lower berry mass, higher total soluble solids content and darker red-yellow hue. The second-crop wines showed significantly higher levels than the first-crop wines of dry extract, titratable acidity, tannins, reducing sugars, total phenols, and anthocyanins (P＜0.05), alongside deeper color intensity and stronger red hue in the wine body. A total of 52 volatile flavor substances were identified from the wine samples. The aroma characteristics of the two-crop grapes wine samples were different. Based on the standards of P＜0.05, variable importance projection (VIP) value＞1 and OAV＞1, 6 key differential volatile flavor substances that could be used to distinguish the two crops grapes wine samples were screened out, including ethyl isopentate, isopentyl acetate, ethyl decanoate, isopentyl octoate, 4-ethylphenol, and 4-ethylguaiacol. The fruity and floral characteristics of the first-crop grape wine sample were more prominent, while the chemical aroma characteristics of the second-crop grape wine sample were more obvious.