A determination of the role of fruit maturity in the sensory properties of
This project attempts to clarify the consequences for wine flavor that result from harvesting fruit at different maturities. It aims to do a complete study (from a sensory and chemical analyses point of view) from the vineyard to the resultant wines. During the current funding period we did the descriptive sensory analysis of the 2006 wines, did chemical analyses of the 2006 wines and had a winemaker panel evaluate the quality of a subset of the 2006 wines. We harvested the 2007 grapes from a single vineyard at six time-points over a fourteen week period (August 23 to November 28, 2007). The samples spanned maturity levels from what would be considered early/normal harvest (average Brix=21) to late harvest (average Brix=30.8). The fresh grapes were evaluated by a trained descriptive sensory panel and by Napa Valley winemakers. The trained panel found subtle but consistent differences among grapes harvested at different times and these results were very similar to those found in 2006. Specifically, lower Brix grapes were more sour in skin and pulp, had more vegetative skins and had greener, more bitter seeds, whereas higher Brix grapes were sweeter, more fruity, more squishy with browner and nuttier seeds and more raisin-flavored skins. The Napa winemakers each used their own method to determine whether the sample grapes were ready to be harvested and in 2006 as well as 2007 they all agreed that grapes from harvest 1 through 3 were not ready to be picked. However, for harvests 4 through 6 there were some differing clusters of winemakers. Additionally, grape berry samples were prepared and frozen for chemical analyses. There were differences between the 2006 and 2007 grapes in the concentration of tannins, anthocyanins and 2-methoxy-3isobutyl pyrazine concentrations. The 2007 wines were made and will be evaluated by a trained sensory descriptive panel (in April) and Napa Valley winemakers (in June). The descriptive analysis of the 2006 wines showed that wines made from grapes with higher initial sugar content were higher in dark fruit, dry fruit and spicy flavors and lower in sourness as well as lower in fresh and cooked vegetative flavors. Additionally, for higher initial sugar concentration musts adding water prior to fermentation had a larger effect on the wine sensory attributes than adding water after fermentation. The winemakers thought that wines made with grapes harvested between 24.7 and 26 Brix were of better quality, and would receive the highest retail price. Wine chemical analyses of 2006 and 2007 wines are on-going.