Issue Date: May 4, 2009
Barrel Chemistry, Chemistry As Label Art
Oak has long been the wood of choice for cooperages that manufacture WINEMAKING BARRELS. But producers of ciders, vinegars, specialty liquors, and even some wines have been trying barrels made of other woods, including acacia, chestnut, cherry, and ash. This practice is opening up new flavor-imparting possibilities, Estrella CadahÍa of Madrid-based National Institute of Agricultural & Food Research & Technology tells Newscripts. But "there is very little information about the chemical composition of these woods that would provide support to predict the sensorial differences found in the wines, vinegars, and spirits produced in these kinds of woods," she says.
So CadahÍa and her colleagues at the institute and Intona, a cooperage in Spain's Navarra region, did what many inquisitive, chemo-savvy agricultural and food researchers might do: They harvested extracts from wood samples, fired up the gas chromatograph/mass spectrometer, and identified wood's volatile—and presumably more sensorially significant—components.
The researchers detected a cornucopia of 110 compounds, 13 of which they say had not been seen before (J. Agric. Food Chem., DOI: 10.1021/jf803463h). The enologically inclined scientists were also able to discern that lignin, wood's second most abundant carbohydrate polymer after cellulose, generally was the primary source of volatile compounds for each wood. Toasting, a heat-treating step in barrel-making, tended to increase concentrations of the compounds.
Some of the woods had signature compounds. Oak, for example, was the only wood with cis and trans isomers of β-methyl-γ-octalactone and isobutyrovanillone, whereas benzyl salicylate and p-anisaldehyde appeared exclusively in cherry, which also had the richest and most abundant overall profile of volatile compounds.
The analysis suggests that each wood has its own composition of volatile chemicals that the scientists say would likely confer a "characteristic sensorial profile," but it also bolsters the age-old wood choice made by most vintners. "The oak turned out to be the most balanced," the researchers remark. "Although it provides a lot of volatile compounds to the aroma and flavor of aged wines, it can do so without masking their primary and secondary aromas."
Winemakers have yet to embrace non-oak barrels, but CadahÍa says the new analysis suggests that nontraditional barrels "can open new expectations" for what she suspects would be "special personality wines."
As the owner and operator of the Roots Run Deep Winery in Yountville, Calif., Mark Albrecht knows he is a modern-day practitioner of an ancient chemical art. And the name of his Cabernet Sauvignon—Educated Guess—along with the most CHEMISTRY-INTENSE LABEL on any wine bottle today, reminds drinkers that winemaking is, in Albrecht's words, "an equal portion of art and science."
The beautiful composition of chemical formulas and scribblings, for which Albrecht and a label designer consulted with wine chemists at places such as Cornell University, Virginia Tech, and the University of California, Davis, honor and annotate a selection of the many reactions by which the juice of grapes becomes one of the world's most beloved and storied fermented drinks. The conversion of sucrose to glucose and fructose and the correlation of sulfur dioxide with acetaldehyde, which can confer a rotten-apple taste at too-high concentrations, are among the half-dozen components of wine chemistry arranged on the label.
The label does have a knack for attracting highly educated clientele. "The Harvard Alumni Club got excited and began pouring it there," Albrecht notes, adding that he receives a handful of e-mails each week, many from people with Ph.D.s. Incidentally, Educated Guess is aged in barrels made of American and French oak.
- Chemical & Engineering News
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