Issue link: http://winesandvines.uberflip.com/i/718029
60 WINES&VINES September 2016 WINEMAKING PRACTICAL WINERY & VINEYARD Visual seed maturity and tannin extraction This study was born out of a discussion about the vagaries of "phenolic" and "seed" ripe- ness and their putative effect on the chem- istry and sensory properties of red wines. The results indicated that visual "seed ma- turity" may play a lesser role in seed tannin extraction than previously thought. In this context, are there other practical reasons to delay harvest until seeds have turned uni- formly brown? The answer is an absolute yes—at least in the maturity range under study (20.3 o -24.9 o Brix). However, rather than seed tannin extrac- tion, other aspects such as sanitary conditions, aromatic development, sugar accumulation and maintenance of natural acidity should be the points of concern. In the grand scheme of things, "visual seed maturity" appears to be a lesser factor, and winemakers who delay har- vest for the sole prospect of getting less seed tannin extraction may be worried for the wrong reasons. We also wanted to tackle the problem of the potential interaction between length of maceration and fruit maturity. Would ex- tended maceration exacerbate the negative characters associated with unripe fruit? Of practical relevance for winemakers applying this technique, our results indicate that the sensory and chemical outcomes of extended maceration are fairly predictable and inde- pendent of fruit ripeness. These sensory and chemical outcomes include a high concentration of protein- precipitable tannins, a low concentration of anthocyanins and wine color and enhanced astringency. Based on these results, ex- tended maceration seems to have a rather negative impact on the sensory profile of red wines. If the stylistic and/or production goal is to merely enhance tannin extraction, perhaps practices such as saignée can be performed to boost tannin retention while also relieving the logistics of tank turnover in the winery. This study has brought about new ques- tions whose definitive answer may have important practical implications. Among them: What are the factors that control tan- nin extraction during extended maceration? Is there a "true" extraction from the seeds occurring during maceration, or rather is there a desorption phenomenon mediated by the action of ethanol on previously bound tannins? What about seed hydration? Do seeds gain weight during extended maceration resulting from water absorption? (Seeds have comparatively lower water activity than the surrounding must.) If so, may this seed hydration result in cell disruption and re- lease of tannins? Are these findings appli- cable to other grape varieties? For early ripening varieties such as Pinot Noir, it will take less time than Merlot to get from 20 o to 25 o Brix, and thus our results should be applicable to Pinot Noir. Cabernet Sauvignon grapes, on the other hand, ripen under conditions of decreasing rate of accu- mulation of growing degree-days, and the metabolic changes occurring between 20 o and 25 o Brix may not be equivalent to those ob- served in Merlot. Federico Casassa is assistant professor of enology and wine sensory analysis in the Wine & Viticulture Depart- ment at California Polytechnic State University in San Luis Obispo. James Harbertson is an associate profes- sor in the Viticulture and Enology program, part of the School of Food Science at Washington State University in Richland. References and additional graphics for this article are available online at winesandvines.com. The complete report can be found in the American Journal of Enology & Viticulture ajevonline.org/content/64/4/437. Promote your wines to leading Zinfandel enthusiasts and extend your winery's relationship in the market. Join Us! We are champions of Zinfandel— America's Heritage Wine Become part of our proud legacy zinfandel.org • 530-274-4900 Zinfandel Advocates & Producers is a 501(c)(3) non-profit organization. ZAP is dedicated to advancing public knowledge of and appreciation for American Zinfandel and its unique place in our culture and history. You know how good your Zinfandel is...