The phenolic component of red wine is responsible for important elements of flavor and mouthfeel, and thus quality of the finished wine. Additionally, many of these phenolics have been associated with health benefits such as reduction of the risk of developing cardiovascular disease, cancer, osteoporosis and preventing Alzheimer’s disease. While the origins, concentrations, and chemistries of the phenolics in a finished red wine are well known, the fundamental mechanisms and kinetics of extraction of these phenolics from grape skins and seeds during red wine fermentation are poorly understood. This lack of knowledge regarding the extraction mechanisms of phenolics during red wine fermentation makes informed manipulations of the finished wine’s phenolic composition difficult.
The skin cell walls of berries play a very important role during the winemaking process as they can form a barrier to release of important flavor compounds, and is a potential adsorption surface. Commercial wineries have observed that polyphenol extraction levels during winemaking may vary based on grape growing region and/or site. Cell wall composition may be one of the important factors influencing this relationship.
In this work, phenolic extractability of Cabernet Sauvignon from two regions within California (Sonoma and Central Coast) has been studied. The study includes the analysis of phenolic berry composition, wine phenolic content as well as skin cell wall composition of three sites per region. Results showed that berry phenolic content is not directly related to the region were the grapes were grown. Within the same region, sites with high and low phenolic berry amounts were found. Regarding the wines, a relationship between region and phenolic content was found. Wines made from Central Coast grapes presented lower phenolic content than those from Sonoma. In order to understand the connection between wine phenolic content and extractability, skin cell wall material was characterized. Partial least squares (PLS) analysis showed that cellulose and uronic acid content might influence the extractability of phenolics during fermentation.
Authors: Cristina Medina Plaza, Nick Dokoozlian, Ravi Ponangi, Tom Blair, David Block, Anita Oberholster
E&J Gallo Winery, 600 Yosemite Blvd, Modesto, CA 95354, USA
Department of Chemical Engineering. University of California, Davis CA 95616, USA
Department of Viticulture and Enology. University of California, Davis CA 95616, USA
Email: cmedinaplaza@ucdavis.edu
Keywords: Extractability, Cell wall, Phenolics, Red wine