Study of Durif (Vitis vinifera L.) berry ripening phases in relationship to wine styles

[摘要] ENGLISH ABSTRACT: The wines of Durif (Petite Sirah) are known for their exceptionally dark colour and astringency (mouthfeel). The goal of this research project was to assess Durif wine styles, profiles and diversity usingsequential harvest. Grapes were harvested from a Durif vineyard in Paarl, South Africa, at differentstages of ripeness on different dates (sequential harvesting) influencing the grape composition, which,in turn, influences wine composition and sensory attributes. There is not only one optimal harvest datefor a vineyard or specific site and several harvest dates could be adequate. This research projectspanned the 2012 and 2013 vintages. The 2012 was used as a diagnostic year to characterize thevineyard plot and the options for harvest timing.Sequential harvesting was used to determine if Durif follows a berry aromatic evolution (Deloire, 2011).The berry aromatic evolution describes wine styles, which can be achieved by determining harvesttime/period using sugar loading as a berry physiological indicator. These wine styles include a fresh fruit(FF) style, a neutral, spicy or pre‐mature fruit style, a mature fruit (MF) style and later an over ripe style(OR). One of the major findings of this research project was calibrating the model of berry sugaraccumulation for Durif to determine picking windows/dates for specific wine styles.The wines made from sequentially harvested grapes were sensorially assessed using the citationfrequency method (Campo et al., 2010).The sensory analysis was used to find the sensory attributes ofwines from two harvest time points corresponding to fresh fruit and mature fruit style wines. The mainaromatic attributes associated with Durif wines in South Africa were identified. Descriptive analysis wasused to rate the intensity of astringency, bitterness, sweetness, sourness and alcohol perception of thewines and how it changes with harvest timingBerry composition was analysed (fructose, glucose, tartaric acid, malic acid, total anthocyanins and totalphenolics) and it was shown that there were significant changes in berry composition during ripening.The evolution of berry composition during the ripening period highlights the importance of optimizationof the picking date. The wine composition, however, is not directly related to grape composition as it iscompounded by the impact of extraction during fermentation (with increasing levels of ethanol withincreasing sugar levels when using sequential harvesting) on tannin and anthocyanin extractability andyeast metabolism (Gil et al., 2015, Fournand et al., 2006). Must composition (pH, TA, Brix) wasmonitored and showed significant differences between early and later harvest dates. Wine compositionof each sequentially harvested wine was analysed.From the trends observed in the frequency of citation method it is suggested that the berry aromaticripening sequence for Durif exists and fresh or mature fruit style wines can be made. Harvest timingcould be defined as picking ten days after the keypoint to produce fresh fruit style wines and twentythreedays to produce mature fruit style wines according to the results of the 2013 vintage.

[发布机构] Stellenbosch University