Location: Horticultural Crops Research2011 Annual Report
1a. Objectives (from AD-416)
Objective 1: Determine effects of water management on wine grape productivity and fruit maturity. Objective 2: Integrate the development and use of analytical methods for the evaluation of phenolic compounds and other chemical indicators of quality in fruit, fruit products, and wine. Objective 3: Determine effects of vineyard and vine microclimate on fruit development, vine productivity, and fruit quality, particularly phenolic compounds.
1b. Approach (from AD-416)
Our fundamental approach for conducting the proposed research is based on interdisciplinary work toward grape production systems and connecting production practices to the quality of the harvested fruit or value-added fruit products. Although each team member is responsible for a distinct experimental focus, overall goals and responsibilities of the contributors overlap because the interactions among system processes and properties transcend disciplines.
3. Progress Report
During the past year, a micro-photochemical reactor for grape tannin evolution was evaluated for suitability. We continue to explore the relationship between agricultural practices (i.e. cover cropping and tilling), biotic stresses (i.e. virus status), and genotypes and their effect on fruit primary and secondary metabolites (i.e. sugars, organic acids, anthocyanins, proanthocyanidins). Wine grapes grown in sunny, arid climates that are strategically supplied with a limited amount of water to enhance grape quality are at greater risk of heat injury and reduced productivity. In 2010, we determined that a white, clay-reflectant spray reduced leaf temperature, increased daily net photosynthesis, and increased vine water use efficiency without affecting aroma compounds in berries, but that the effectiveness of the clay-reflectant declined under limited water supply. This finding is important because it identified growing conditions for wine grapes under which a spray application of clay-film could be expected to reduce heat injury and enhance productivity.
1. Grape tannin evolution. Understanding the kinds and quantities of food quality components naturally present in fruit is critical for selective breeding of better fruit traits to improve US production, fruit product processes, and ultimately what reaches the consumer. A controlled model wine study was carried out to examine the evolution of grape skin and seed tannins to assist our understanding of how these compounds change as they oxidize. All monomer and polymer oxidations were dependant on initial solution concentration. As expected, monomer and polymer solutions showed a decrease in measureable phenolics. Due to the complexity of new structures that are formed, and the limitations of currently available analytical techniques, tannin decomposition by oxidation is difficult to study.
2. Black raspberry phytochemicals. A large number of black raspberry samples (n=190) were tested for their anthocyanin (natural phytochemical) content. These results uncovered a vast range of pigments existing within a single species. We also found new black raspberry mutants that contained a novel anthocyanin profile with rutinoside, compared to all previous black raspberry anthocyanin profiles lacking anthocyanins containing rutinosides. This information will provide a valuable baseline for researchers tracking anthocyanin molecular pathways, nutritionists wishing to study the health effects of these compounds, breeders interested in developing new cultivars with improved fruit chemistry traits, and nutraceutical product developers.Ou, C., Du, X., Shellie, K., Ross, C., Qian, M. 2010. Volatile compounds and sensory attributes of wine from cv. Merlot (Vitis vinifera L.) grown under differential levels of water deficit with or without a kaolin-based, foliar reflectant particle film. Journal of Agricultural and Food Chemistry. 58:12890-112898.