Evaluation of the Influence of Common Viticultural Practices on the Chemical and Sensory Characteristics of Wine

AVF Proj. ID: 221 / /Cat.:
Primary Investigator(s): David Block, Lynn Epstein, Sanliang Gu, Douglas Gubler, Russell Molyneux, Jean VanderGheynstby

The goal of this project is to find critical viticultural parameters that affect the chemical and sensory characteristics of the final wine. Once these parameters are identified, winemakers and vineyard managers can use computational methods developed in our lab in order to suggest the best vineyard practices to use to achieve specific target characteristics in their final wine. In the past, we have taken two complementary approaches to this problem. First, we have developed tools for searching through large existing databases of viticultural information to find the most critical factors. A Decision Tree Analysis algorithm has been developed in our lab for this purpose, and several decision metrics have been evaluated with an exact probability metric, Po, being chosen as the most effective. However, due to a lack of appropriate commercial databases combining viticultural data with sensory or chemical characteristics of finished wine, we switched the focus of this part of the grant to study the effects of weather on Cabernet quality using historical weather and wine quality data. Our initial models have fairly good predictive capacity. Second, we are producing Cabernet Sauvignon wines from existing viticultural trials at the Oakville Experimental Station. For the past three harvests, we have produced 37 wines from grapes harvested from vines differing in parameters such as rootstock, irrigation, trellis, pruning, row orientation, and vine density. Chemical analysis of the wines from the first harvest was completed in the previous grant year; sensory analysis of the first year wines was completed this year yielding some interesting preliminary results. The data indicate that all eight aroma descriptors (cocoa, blackberry, cherry, dried fruit, green pepper, black/white pepper, cooked vegetable, and olive) are functions of the viticultural treatments studied and all except cocoa are a function of crop weight/pruning weight ratio. We are now working to find the underlying causes of these effects and have begun to set up more systematic studies examining the factors identified as important. Finally, a systematic microoxidation has been initiated to examine the effect of this procedure on vegetative characteristics and phenolic profile.