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p r a c t i c a l w i n e r y & v i n e ya r d J U ly 2 0 1 4 69 with another phenolic compound created by the toasting process, 4-methyl- 2,6-dimeophenol (see Figure 2). The evo- lution of these two phenolic compounds can explain why the toast impact can seem very dominant in the first few months the wine is in barrel, especially with open grain, and then is tamed down as the wine ages in the barrel. The second layer would be best charac- terized by pastry-like aromatics such as vanillin. Our analysis shows this com- pound only starts being released in signifi- cant quantity in the wine after 60 days in the barrel, once the wine soaks into the wood (see Figure 3). Here there is very little difference between the open and tight grain. The fresh oak and spice aromatics are likely to come predominantly from a third layer, deeper in the stave. At that depth within the stave, the impact of the toasting process has been much less. The wood has not been modified as much by heat and flames. The concentration in the wine of cis- whisky-lactones and eugenol, for exam- ple, increase after two to three months and even faster after eight months. In addition, the concentration of these com- pounds is significantly higher for the wine aged in tight-grain barrels (see Fig- ures 4 and 5). Tannins interact and soften The studies found that open-grain barrels release more tannins (ellagitannins) into the wine over time than tight-grain bar- rels. We expect this is due to more fiber and parenchyma material being in contact with the wine. But for both open grain and tight grain, tannins released by the oak barrel follow a very different trend compared to other compounds. Their concentration increases linearly between one and eight months, and then decreases after eight to nine months in barrel, as the tannins soften. This softening is due to several reac- tions: polymerization, oxidation and pre- cipitation as well. The most important is the polymerization, by which tannins from the grape (polyphenols) combine with tannins from the oak (ellagitannins). This combination forms new tannin com- pounds that contribute to a softer, rounder, silkier mouthfeel. By polymerizing, tannins lose some of their astringency. This is why it is often said that tannins from the oak provide a "coat- ing," a softening of the grape tannins. Tan- nin combinations are believed to be a critical element in the perfection of many gustative dimensions of wine (structure, tex- ture, density, creaminess and suppleness). Among the new tannin compound families created by this polymerization process, one is particularly striking: Acu- tissimin A. It is formed by the combina- tion of a polyphenol from the grape (flavonoid) and an ellagitannin from oak (vescalagin). In 2003, scientists estab- lished for the first time that red wine aged in oak barrels contained flavono- ellagitannins formed during aging, and which were not present in oak or wine separately. Among these flavono-ellagi- tannins, scientists also established that Acutissimin A had an extremely high anti-carcinogen effect.** We would like to think this is the French coopers' contribution to the French paradox. Perhaps there is a hid- den attribute to oak tannins and grain, beyond being a crucial tool to adapt élevage to the specificity of each wine. PWV * An experiment was carried out with medium- toasted, 30-liter barrels made with tight grain and medium/open grain. The wine was red Bordeaux from Margaux AOP. Two barrels per grain type were filled after malolactic fermentation, and the wine was analyzed for several compounds at regular intervals during one year of élevage. The wood-wine exchange was greater in this small barrel because the wood contact surface with the wine in a 30L barrel is 2.3 times greater than for a 225L barrel. ** Dr. Stéphane Quideau at Institut Européen de Chimie et Biologie of Pessac, together with other scientists, found that when the oak tannin vescalagin interacts with phenols in red wine aged 18 months in barrels, Acutissimin A is created. In separate studies this phenolic compound has been shown to be much more effective than certain drugs in stopping the growth of cancerous tumors. "DNA Topoisomerase Inhibitor Acutissimin A and Other Flavono-Ellagitannins in Red Wine," Dr. Stéphane Quideau et al., November 2003, Angewandte Chemie International Edition. W I N E M A K I N G Open Grain Tight Grain Aging duration (days) 30 25 20 15 10 5 0 0 50 100 150 200 250 300 350 Ellagitannins (mg/L) Ellagitannins (mg/L) Figure 6. open/medium-grain barrels release more ellagitannins than tight grain. In both grain types, concentration of ellagitannins increases after two months, peaks around eight months, and then decreases, as tannins polymerize. Cis-Whisky lactone content/PercepŸon threshold Aging (days) 5 4 3 2 1 0 0 73 119 253 340 Open Grain Tight Grain Figure 4. tight-grain barrels release more whisky lactone (associated with fresh wood smell, coconut and whisky) over time. the per- ception threshold is 74 ug/L in red wine. verti- cal axis shows ratio between the measurement and the perception threshold in ug/L. Open Grain Tight Grain Aging (days) 30 25 20 15 10 5 0 0 50 100 150 200 250 300 350 Figure 5. tight grain releases larger concen- tration of eugenol. the perception threshold can vary, therefore the graph only shows concentration. aromatic associations are cooking spices and cloves. the softening of tannins through polymerization. the acutissimin a family is an example of these new compounds formed during barrel aging.