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28 W i n e s & V i n e s M A R C H 2 0 1 4 Inquiring Winemaker T I M P A T T E R S O N S plit up the harvest of a small vineyard among five boutique wineries, do the winemaking in all cases along similar lines, and no one will be surprised when the results in the bottle all taste and smell noticeably different. But open up five barrels from the same cooperage, with the same toast level, and your jaw may drop at the variation on display. The further you dig into barrel variation— between cooperages, between barrels from the same cooperage, between the staves in a single barrel, between the ends and the bellies of the staves—the more of it you find. Tanks are pretty much tanks, plus or minus a few bells and whistles; barrels are more like snowflakes. The next barrel you buy from Fils et Frères may not be like the last one, and the order from Quercus Expensivus may not really echo the one you used in your barrel trial. This is not the warm-up for a flaming exposé of the shocking mendacity of the world's great cooperages, a sordid tale of fraud in the woodlot. It's a story of how hand-made, artisan products can't and don't come out identical. In fact, we probably don't want barrels to be utterly uniform widgets. But the breadth of variation is something winemakers have to understand and keep an eye on, and every now and then, it might be worth the hassle to open the hood on one and see what's inside. Tom Collins, barrel detective This column isn't exactly ripped from the headlines, but it was inspired by a presenta- tion given by Tom Collins, director of the Food Safety and Measurement Facility at the University of California, Davis, during an all-day session held at Davis in December to focus on winemaking measurements. Before coming to Davis, Collins worked for Trea- sury Wine Estates, where he launched a proj- ect to understand how barrel production and toasting affected oak aromatics, in order to better match cooperage practices with specific wine styles. His talk drew from both the results of the Treasury study and his own later work. Barrel wood contains certain aromatic com- pounds from the start, just by virtue of being oak, like oak lactones (fresh oak and coconut) and others that get produced or amplified by toasting, like guaiacol (smoky, spicy). The duration and temperature of the toasting and barrel-assembly process are the main drivers of the aromatic compounds and properties of the final barrels, and so Collins and his crew inserted thermocouple sensors at various points along the length of beaucoup de staves and tracked them through the toasting pro- cess. Later, they took apart a number of barrels and tested wood scrapings—again, from dif- ferent parts of different staves—and analyzed the aromatic compound content. Since Collins is still working up his data for formal publication, I will spare you some of the charts, tables and statistical numerology. Let's just say he found a ton of variation—a heap, a bunch, a bushel and a peck—at every stage from tree to finished barrel. It all starts with the wood. Different trees— even ones raised right next to each other—go under the axe with slightly different chemical composition and tissue structure. Staves cut from different parts of the tree can differ, and how staves are cut and planed can leave them rougher or smoother, which affects how the wood later responds to heat. And then there's the fire part. Because the fire pot is down on the floor, and the staves are sticking up three feet into the air, it is guaran- teed that the ends of the staves will get more heat treatment than the belly, which virtually guarantees every stave in every barrel will bridge at least two official toast levels and bring two sets of aromatic goodies to the party. Different staves headed for the same barrel may also get slightly differently toasted. Even if the overall fire pot temperature is well-con- trolled, adding a piece of wood to the fire makes that side of the circle hotter (at least for a while) than the other side, generating more of compound X and less of compound Y. Color, it turns out, is not a very reliable indicator of actual toast level and compound content. But the pictures Collins showed of all the staves from a single barrel lined up side by side, with the light and dark areas splattered around like a Jackson Pollack, were indeed worth a thousand words. My favorite from Collins' list of factors that can affect stave and barrel toast levels is what kind of ventilation system is in place in a particular cooperage and how well it is working that day. If these are some of the factors that influ- ence the supply of barrels, the demand for barrels can play a role, too. Mel Knox, barrel broker extraordinaire, distributor of both Francois Frères and Tarransaud, pointed out that if a major wine region like California has a short crop in a particular year, the sup- ply of barrel wood will back up, meaning some staves will dry another year, changing their composition and toastability. Are so-called oak alternatives more reli- able? According to Collins, if they come from Do You Know What's Inside Your Barrel? Highlights • Research has shown a high degree of variability in the toast levels and aromatic compound content of oak barrels. • Because barrels are hand-made prod- ucts, some degree of variation—even along a single stave—is inevitable. • Wineries can benefit from testing barrel aromatics, using the analysis to augment sensory evaluation.