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72 WINES&VINES October 2018 WINEMAKING PRACTICAL WINERY & VINEYARD considerable. Anthocyanin content varied up to about two-fold in the same cultivar, and tannin concentration varied up to 1.5-fold in response to ripeness or alcohol. These varia- tions gave a two- to three-fold difference in the A:T ratio for the same variety. This study found the A:T ratio was a very poor predictor of polymeric pigment concen- tration. The best single predictor for poly- meric pigment formation over time was initial wine anthocyanin content, which in- creased with more fruit maturity. This result contradicted the importance of A:T from previous literature. Although initial wine anthocyanin content in this study was a strong polymeric pigment predictor, fruit anthocyanin levels did not di- rectly correlate to wine anthocyanin content. Based on findings from this study, winemakers should focus on the initial anthocyanin con- centration of wines — not fruit anthocyanin concentration — because it was the strongest predictor of polymeric pigments in Cabernet Sauvignon and Syrah wines. Maximize polymeric pigmentation This study found that higher fruit maturity increased anthocyanin concentrations and that higher wine alcohol increased tannin levels. Both the increased ripeness and al- cohol led to the highest polymeric pigment concentrations. Therefore, the easiest way to maximize polymeric pigment formation is to use ripe, mature fruit (24°-28° Brix) and make medium- to high-alcohol (14%- 17%) wine. In regions or growing seasons where it is difficult to harvest mature, ripe fruit—but tan- nin levels are not a problem—the focus should be to maximize fruit and wine color. Growers can use vineyard-management practices such as keeping the canopy open, growing low-vigor vines, removing leaves in the fruit zone and implementing deficit-irrigation strategies to encourage maximum color (anthocyanin) development in the fruit. But once grapes are picked, it is difficult for winemakers to increase color; extraction of anthocyanins in the winery is relatively quick, and concentration reaches maximum levels early in fermentation and then declines. The trend of cold soak—holding the must at a low temperature for hours to days before fermentation—has become popular in some regions as a technique to increase color, al- though there is conflicting research on its effectiveness. Cold soak might extract more anthocyanin temporarily, but it does not ex- tract additional tannins and research shows no increase in polymeric pigment formation from cold soak. 1 To maximize polymeric pigment formation in low-tannin varieties such as Pinot Noir or Syrah, use vineyard and winery techniques to increase both color (see above) and tannins in the wine. Efforts to increase tannin levels are most successful at the winery level, although some research found that low-vigor vines within an individual vineyard had higher grape-tannin levels. No relationship has been found between tannin levels of fruit and tannin concentration in the resulting wine. It is difficult to predict tannin extraction from fruit ripeness or matu- rity, but earlier research 2,3,4,5 found that wine- makers can manipulate tannin extraction through extended maceration (minimum of 20 days needed to see differences), increased fermentation temperature (keep as warm as conditions allow without killing yeast) and higher alcohol (an increase of 2%-3% above normal winemaking practices). This article was condensed from the report "Effects of Berry Maturity and Wine Alcohol on Phenolic Content during Winemaking and Aging," published in the Ameri- can Journal of Enology & Viticulture, January 2018. Dr. Caroline Merrell was a post-doctorate research associate in the Viticulture and Enology Program of Washington State University, where she focused on wine chemistry and sensory research. She recently joined California's Jackson Family Wines as a research and development chemist. Melissa Hansen, research program manager for the Washington State Wine Commission, works to make viticulture and enology research supported by the Wash- ington wine industry more accessible to the state's winemakers and grape growers. Hansen spent nearly 20 years as a journalist for Good Fruit Grower magazine and was involved with California's table-grape and tree-fruit industries for 15 years. To see the bibliography for this article, go to winesandvines.com and search under Magazine › Features › October 2018 ACCELERATED DEVELOPMENT OF BOTTLED WINE S ince polymeric pigment formation occurs over time, the trial needed to include bottled wine development, which can add years and expense to the research. To accelerate the aging process, bottled research wines were held in an incubator at higher-than-normal temperatures of 30° C (86° F). Incubated wines were chemically compared to cellar-aged wines at 15° C (60 o F) to determine how the accelerated aging compared to traditionally aged wines. Previous studies found that a 10° C increase in temperature increased the rate of aging reactions by a factor of 2. This study chose 30° C because it would increase the speed of aging reactions by 2.5-fold, but without risk of evaporation or chemical degradation in the bottled wine. One month of incubator aging was determined to be the equivalent of one year in a com- mercial cellar for phenolic development. The incubator-aging technique of four months resulted in the equivalent of wine stored for four years at cellar temperature for polymeric pigment analysis. This accelerated bottled-wine development was for research purposes only and is not recommended as a wine storage technique. Wine aroma evaluation was not part of the overall study nor part of the accelerated aging experiment. Temperatures this high are likely to have a negative effect on aromas. Polymeric pigment formation increased with both increased alcohol and maturity. Note: Wines are represented by harvest maturity (unripe 20° Brix, ripe 24°, overripe 28°) and alcohol level (low 11-12%, medium 14-15%, high 17%). EFFECT OF FRUIT MATURITY AND ALCOHOL ON POLYMERIC PIGMENTS 500 400 300 200 100 0 Unripe- Low Unripe- Medium Unripe- High Ripe-Low Ripe- Medium Ripe-High Overripe- Low Overripe- Medium Overripe- High Total Polymeric Pigment (mg/L) n Syrah n Cabernet Sauvignon