Pinot Noir grape colour related phenolics as affected by leaf removal treatments in the Vipava Valley

Wine colour depends directly on the quantitative and qualitative profiles of anthocyanins, flavonols and hydroxycinnamic acids, as well as on their involvement in polymerization and co-pigmentation reactions. Pinot Noir is a grape variety with a low natural colour potential, often combined with problems of low colour stability for its wines during aging. The influence of leaf removal timing on grape colour related polyphenols was observed during maturation and at harvest time for the 2009 vintage "real scenario" conditions in two different vineyards in the Vipava Valley (Slovenia), known for its warm but windy climate. With different timing of leaf removal, a different microclimate can be achieved, with different light exposure for the specific plant tissue and different temperatures on berry surfaces. Phenolic compounds were characterised and quantified using HPLC/Vis. Three classes of polyphenols were affected by leaf removal timing, but with differing intensities and with some differences between locations. Hydroxycinnamic acids were affected only slightly, mostly at the beginning of the maturation period. Anthocyanins were significantly affected, while flavonols were the most affected by treatments in both vineyards and their concentration was clearly related to modification of the light within the canopy.