Aroma components analysis of Summer Black grape under two-crops-a-year cultivation

【Objective】The aroma components in summer and winter grapes of Summer Black grape cultivated in twocrops-a-year system were analyzed, in order to provide theoretical basis for improving its aroma quality and promotion of two-crops-a-year cultivation.【Method】Eight-year-old Summer Black grape vines which cultivated under a two-crops-ayear cultivation were used as the material, the summer and winter grapes were collected at veraison, ripening and late ripening stages. Headspace-solid phase microextraction(HS-SPME) and gas chromatography-mass spectrometry(GC-MS) were used to qualitatively and quantitatively analyze the aroma components of these three stages of summer and winter grapes, and the changes of duration days, meteorological indexes and berry physicochemical indexes in different developmental stages between summer and winter grapes were monitored.【Result】From budding to ripening, the daily temperature increased gradually in summer grapes, while decreased gradually in winter grapes. In winter grapes, the veraison was earlier and the duration of ripening process was longer than summer grapes. The soluble solids content and titratable acids content in ripen winter grapes were higher than that in summer grapes. A total of 48, 51, 47 and 52, 56, 56 aroma components were identified in summer and winter grapes at veraison, ripening and late ripening stages, respectively, including aldehydes, alcohols, esters, ketones, terpenes and acids. The total content of aroma components in the three stages of winter grapes were 472.83, 1020.27 and 836.43 μg/L, respectively, which were all significantly higher than that in summer grapes(459.39, 638.57 and 659.20 μg/L, respectively) (P<0.05, the same below). The content of aldehydes was the highest in ripen Summer Black grape, followed by alcohols. In ripen summer and winter grapes, the contents of aldehydes were 446.34 and 600.18 μg/L respectively, and the contents of alcohols were 120.21 and 163.44 μg/L respectively. The monomer aroma components were mainly C₆ compounds, among which the compound with the highest content was hexanal with grass and apple fragrance, followed by 2-hexanal, (Z) -3-hexanal and hexanol, showed herbaceous and fruity flavors. The content of the above monomer aroma compounds in winter grapes of Summer Black grape was all significantly higher than that in summer grapes.The most representative eight differential aroma compounds in ripen summer and winter grapes were 2-hexanal, ethyl acetate, citronellol, phenethyl alcohol, nerol, (Z) -3-hexanal, geraniol and ethyl caprylate, and the contents of these differential compounds in winter grapes were significantly higher than that in summer grapes.Through the analysis of climate conditions, compared with the summer grapes, the cold environment and drier climate in the late growing season of winter grapes were the main reasons for the significantly higher aroma content in winter grapes of Summer Black grape than that in summer grapes.【Conclusion】The difference of aroma compounds composition and contents between summer and winter grapes under two-crops-a-year cultivation is the result of the comprehensive effect of meteorological factors, the climate conditions in winter grapes growing seasonis more favorable for grape aroma quality improvement.