Effects of partial dehydration techniques on the metabolite composition in ‘Refošk’ grape berries and wine

Abstract

The aim of the study was to investigate the impact of the on-vine double maturation raisonnée (DMR) and off-vine berrypartial dehydration in the chamber (PDC) on the chemical characteristics of the grape and wine grapevine cultivar ‘Refošk’. A liquidchromatography-mass spectrometry (LC-MS) system was used for the identification and quantification of phenolics and the HPLC forsugars and organic acids. Berries subjected to DMR partial dehydration reached technological maturity (18.5 °Brix) within 14 days ofcane cutting and those under PDC in 22 days upon harvest. The greatest decline in berry weight was recorded in the PDC treatment(14%), followed by the DMR technique (approx. 8%). Both dehydrations significantly increased titratable and total acidity in berry andwine, while the pH level was significantly lower in DMR treated berries. Compared to PDC, DMR significantly increased the contentof total flavonols and anthocyanins in berries and wine, as well as the total flavanols in berries and stilbenoids in wine. DMR treatedberries contained 1.7-fold higher content of total anthocyanins, up to 2-fold higher content of total flavonols, and 1.6-fold highertotal phenolic content in the skin compared to those from PDC treatment. Moreover, it increased the content of total anthocyanins,stilbenoids, and flavonol glycosides in wine. On the other hand, PDC treatment showed greater impact on phenolics in wine, especiallywith an increase of total hydroxycinnamic acids, flavanols, and total phenolics but with a decrease in anthocyanins contents. The studysuggests that berries subjected to DMR respond differently to partial dehydration than those subjected to PDC, which was evident fromthe accumulation of secondary metabolites. Undoubtedly, DMR showed interesting results regarding berry and wine composition andtherefore it could be introduced in the vineyard for production of dry wine as well.