Browsing by Author "Wiid, Stephanie Cezanne"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Study of Durif (Vitis vinifera L.) berry ripening phases in relationship to wine styles
    (Stellenbosch : Stellenbosch University, 2016-03) Wiid, Stephanie Cezanne; Deloire, Alain; Buica, Astrid; Stellenbosch University. Faculty of Agrisciences. Dept. of Viticulture and Oenology.
    ENGLISH ABSTRACT: The wines of Durif (Petite Sirah) are known for their exceptionally dark colour and astringency (mouth feel). The goal of this research project was to assess Durif wine styles, profiles and diversity using sequential harvest. Grapes were harvested from a Durif vineyard in Paarl, South Africa, at different stages 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 date for a vineyard or specific site and several harvest dates could be adequate. This research project spanned the 2012 and 2013 vintages. The 2012 was used as a diagnostic year to characterize the vineyard 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 harvest time/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 sugar accumulation for Durif to determine picking windows/dates for specific wine styles. The wines made from sequentially harvested grapes were sensorially assessed using the citation frequency method (Campo et al., 2010).The sensory analysis was used to find the sensory attributes of wines from two harvest time points corresponding to fresh fruit and mature fruit style wines. The main aromatic attributes associated with Durif wines in South Africa were identified. Descriptive analysis was used to rate the intensity of astringency, bitterness, sweetness, sourness and alcohol perception of the wines and how it changes with harvest timing Berry composition was analysed (fructose, glucose, tartaric acid, malic acid, total anthocyanins and total phenolics) 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 optimization of the picking date. The wine composition, however, is not directly related to grape composition as it is compounded by the impact of extraction during fermentation (with increasing levels of ethanol with increasing sugar levels when using sequential harvesting) on tannin and anthocyanin extractability and yeast metabolism (Gil et al., 2015, Fournand et al., 2006). Must composition (pH, TA, Brix) was monitored and showed significant differences between early and later harvest dates. Wine composition of each sequentially harvested wine was analysed. From the trends observed in the frequency of citation method it is suggested that the berry aromatic ripening sequence for Durif exists and fresh or mature fruit style wines can be made. Harvest timing could be defined as picking ten days after the keypoint to produce fresh fruit style wines and twentythree days to produce mature fruit style wines according to the results of the 2013 vintage.