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Leaf removal (LR) treatments improve the photosynthetic capacity of the remaining leaves and induce flavonoid synthesis as a stress response in the common grapevine (Vitis vinifera L.). However, excessive exposure of grape berries to UV‐B radiation as a result of cultural practices in the Mediterranean climate may have negative effects on berry composition. This 2‐year study determined the effects of defoliation on the autochthonous red grape variety 'Babica' in a Mediterranean climate (wine‐growing region Dalmatia, Croatia). Six leaves were removed before flowering (FLR) and at the end of véraison (the onset of grape ripening; VerLR) and were compared to the untreated control. Yield parameters, sugar content, grape must pH, total polyphenols (TP), total anthocyanin (TA) content, and individual anthocyanin compounds were measured in grape skin extracts and wines. However, the greater mean daily temperature during the vegetation period and lesser rainfall before harvest in 2018 increased yield per vine, average cluster weights, density, and total acidity, compared to 2017. Both defoliation treatments significantly reduced TP in grape extracts, but these differences were not observed in wine. Compared to the control (NLR), VerLR treatment significantly reduced TA in grape skin extracts and wine. Significantly lesser TP concentrations, in grape skin extracts and wine, as well as TA were noticed during the 2017 season. VerLR treatment reduced the concentration of nine individual anthocyanins compared to the control in grape skin extracts, while this effect was not observed in wine. Season year was a statistically significant source of variability of the individual anthocyanin contents in wine. Under specific environmental conditions LR can decrease polyphenols, especially anthocyanins, and negatively impact grape and wine quality. [ABSTRACT FROM AUTHOR]

Abstract: Twelve samples of commercially available wines produced in three different wine-growing sub-regions of Croatia were analysed, to determine their polyphenolic content and associate the concentration levels of these compounds with the geographical origin of wine. Total phenols were analysed according to the Folin–Ciocalteu method. Fifteen individual polyphenols were analysed by a reverse-phase HPLC method that used gradient elution and diode array detection. Wines made in Central and Southern Dalmatia were richest in total phenols and individual polyphenols. Flavonols and trans-resveratrol pattern were the basis for the classification of samples according to their geographical origin and type of wine. [Copyright &y& Elsevier]