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January 2015 Wines&Vines 153 wine eAst winemAking sumer satisfaction has been posi- tively correlated to color in a variety of products including red wines. Darker color enhances the perception of fruit and flavor in- tensity, and what red wine fan doesn't look for intensity and rich fruit? Anthocyanins, the pigmented phenolics responsible for wine color, are located in the vacuoles of hypodermal cells, right under the grape skin. To move into the juice, anthocyanins have to first exit the vacuoles and then the cells themselves—a process made easier by physical cell damage. Subsequently, anthocyanin extrac- tion occurs more readily in mature grapes with softened fruit tissue. During winemaking, traditional belief dictates that extraction is enhanced late in fermentation by higher alcohol content, but the bulk of evidence indicates that peak anthocyanin extraction actu- ally occurs around the fourth day of fermentation, and slows to nothing after about the 10th day. Moving anthocyanins into must is just the beginning of the story, however. In their mono- meric (non-bonded) state, indi- vidual anthocyanins are unstable at wine pH, which pushes them to change into colorless forms. Last- ing pigmentation is achieved when anthocyanins bind with other compounds to form stable complexes. While scientists have hardly scratched the surface of the complex chemical reactions that produce wine color, two phenom- ena have been well described: co- pigmentation and polymeric pigment formation. Young color Copigmentation, which is most important in the visual appear- ance of young red wines, occurs when anthocyanins bind non-co- valently with other phenolic co- factors. This binding stabilizes the anthocyanin in a colored form, changing light absorption so that color deepens and moves from red toward blue. In V. vinifera culti- vars, the cofactor to anthocyanin ratio is generally around 0.05:2. Copigment formation appears to be limited by cofactor availability, extraction rate and possible sorp- tion onto other grape or yeast components. Studies of copigmentation have largely focused on reactions in- volving malvidin-3,5-diglucoside, the predominant anthocyanin in V. vinifera. In hybrid cultivars, where non-malvidin anthocyanins and monoglucosides are more common, the color shift and en- hancement that comes with copig- mentation is less pronounced. This is one reason that hybrid red wines are described as having "non-vinif- era" color. It's also likely that hy- brid red wine color is affected by the type and amount of acylated non-malvidin anthocyanins, i.e., monomers of perlargonidin, cyani- din, peonidin, delphinidin or pe- tunidin bound to cinnamic or aliphatic acids. These acylated anthocyanins appear in colors ranging from orange to pink and blue, and they may result in "un- typical" red wine color. At the moment, there's more empirical data about production methods that may increase copig- mentation than solid understand- ing of the science that makes it happen. The traditional practice of cofermenting low- and high- cofactor cultivars together (such as Trebbiano and Malvasia with Sangiovese) to enhance color is well documented, but the degree of copigmentation achieved varies by cultivar, region and year. Both high alcohol content (approaching 16%) and warmer fermentation temperatures have been found to disrupt copigmentation forma- tion. In the latter case, extraction of both anthocyanins and cofac- tors increase, but reaction thermo- dynamics limits their bonding capability. long-term color The second type of stable bound anthocyanin compounds is called polymeric pigments, but the moni- ker is deceiving, as not all "poly- meric pigments" are polymers, or pigmented. The name was origi- nally applied to compounds that were observed to resist sulfite bleaching, and it has become a sort of blanket term for any com- plex with anthocyanins bound covalently with other wine com- pounds. Polymeric pigment for- mation shifts color toward brick red and provides the primary source of color in wines upwards of two years old. EASTERN WINE LABS Serving the Analytical needs of East Coast Wineries WWW.EASTERNWINELABS.COM Ph 609-859-4302 Cell 609-668-2854 chemist@easternwinelabs.com AOAC Member EasternWineLab_Mar09.qxp 1/22/09 9:47 AM Page 1 - B E C O PA D - Y E A S T & E N Z Y M E S - C R U S H PA D E Q U I P M E N T - S T E R I L E F I LT R AT I O N - W I N E R Y H O S E - O A K A LT E R N AT I V E S Case By Case Wine and Grape Supplier Your Source for World Class Wine Grapes and Bulk Wines Serving wineries nationwide on a Case By Case basis East and West Coast varieties available: R Winegrapes R Bulk Wine R Juice R Shiners Jim, Owner Northern California Office (707) 671-4126 • jim@casebycasebrokers.com Tom, Domestic and International Sales Southeast Office (864) 401-2297 • tom@casebycasebrokers.com www.casebycasebrokers.com