Effect of Cluster Sunlight Exposure on Rotundone Concentration in Noiret Grapes and Wine

Download or read book Effect of Cluster Sunlight Exposure on Rotundone Concentration in Noiret Grapes and Wine written by Laura Homich and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: It is generally recognized that wine quality begins in the vineyard; therefore, it is important to understand how the vineyard environment and management techniques impact the development of specific compounds which contribute to or detract from wine quality. The aroma impact compound rotundone was recently identified as the main contributor to the spicy, black pepper aroma in many grapes, wines, herbs, and spices. While the mechanism of rotundone formation remains unknown, it has been determined that mesoclimate plays an important role. Knowing this, studies have suggested that viticultural practices which alter canopy microclimate, such as fruit zone leaf removal, may be useful tools for manipulating rotundone concentrations in the fruit and therefore black pepper character in wines. This two-year study sought to identify the presence of rotundone in the Noiret (interspecific hybrid of Vitis) variety and to determine if and how the timing and duration of cluster sunlight exposure affect rotundone concentration in the fruit, and black pepper aroma intensity in the vinified wines. The timing of sunlight exposure was evaluated through comparison of pre-veraison (LR) and post-veraison (PVLR) single event leaf removal treatments, while the duration was assessed through comparison of a maintained 100% sunlight exposure (MSE) treatment with an undefoliated control (CON). Enhanced point quadrat analysis (EPQA) was used to evaluate the impact of each treatment on vine canopy density and light availability in the fruiting zone. Stable isotope dilution analysis, solid phase extraction and microextraction, and gas chromatography-mass spectrometry techniques were used in combination to assess rotundone concentration and the dynamics of its development in the fruit. Descriptive analysis was used to evaluate the black pepper aroma intensities in wines vinified from the vineyard treatments, and these ratings were plotted against wine rotundone concentrations to determine if a correlation exists. This study successfully identified the presence of rotundone in the Noiret variety for the first time. During both seasons, the MSE treatment reduced canopy density and increased fruit light availability as compared to the CON. The leaf removal treatments did not result in differences in canopy characteristics at any time during 2014. In 2015, however, fruit sunlight exposure was increased in the leaf removal treatments, albeit only temporarily. Rotundone was not detectable in fruit sampled before or at veraison. No significant differences in rotundone concentration for either treatment comparison were observed in the 2014 fruit at harvest; however, rotundone concentrations after veraison were significantly (p