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56 P R A C T I C A L W I N E R Y & V I N E YA R D July 2015 W I N E M A K I N G observed the decrease of vanillin contact during barrel fermentation and élevage in the presence of yeast lees, products of transformation being low odorant vanil- lyl alcohol and vanillyl-ethyl-ester. 5,17,18 The trans-2-nonenal, as any other ali- phatic aldehydes, could interact with tan- nins and sulfur dioxide. L. Blanchard and T. Tominaga have respectively identified furfuryl-thiol and 5-methyl-2-furameth- anethiol (coffee-like smell compounds with very low odor thresholds: 0.4 ng/L and 50 ng/L) as products of transforma- tion of furfural and 5-methylfurfural, respectively, in wine medium. 3,21.22 The survey of a large set of wines aged in oak barrels shows quite differ- ent kinetics of accumulation, but also degradation of main wood compounds in wine (Figure 1). É levage of wine is one of the essen- tial steps in the elaboration of great wines. However, it is well known that sensory results of élevage are not often consistent and pre- dictable. This gives the operation charm because it has an artisan character. But today winemakers desire to obtain results as consistent and as close as pos- sible to their expectations. That is why a robust model using the chemical analysis of wood as input data and allowing the prediction of sensory perception of wood in wine is required. The major difficulties to overcome for development of such a model are the natural variability of wood extractives, knowledge of wood compounds' evolu- tion during élevage and the topic we will see in more detail below: the complexity of the interaction between oak flavors and wine components. Sensory-active wood compounds' evolution in wine Among odorant chemicals, only a few called "impact compounds" can be per- ceived in wine on tasting. The odor activ- ity value (OAV) of a flavor compound (ratio between the amount in wine/sen- sory threshold) is an indicator of the pos- sibility of it being the impact. Élevage brings complexity to wine due to leaching of several strong odorant chemi- cals from the wood and their further transformation into the wine. Important wood chemicals, which could be sup- posed to be impact molecules, include naturally present cis and trans methyl- octalactone (whisky lactones, with a coco- nut flavor in pure state), trans-2-nonenal (sawdust smell), toasting releasing vola- tile phenols: guaiacol, 4-methyl-guaiacol and eugenol (spicy and smoky smells) and vanillin (vanilla smell). On the other hand, some of them are the objects of modification in a wine medium. P. Chatonnet and P.J. Spillman Figure 1. Evolution of some oak flavor compounds in barrel-aged wine. Note: The data used for this plot represents average concentration of studied compounds within a three-vintage survey; cis-WL = cis-whisky-lactone. Source: Seguin Moreau 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 0 2 4 6 8 10 12 14 Vanillinx10 4-methyl-guaiacol x100 Furfural Cis-WL x 10 Months of aging Concentra on of compounds µg/L This text edited and expanded by the author from first publication: Fall 2011. Andrei Prida, Tonnellerie Seguin Moreau, Merpins, Cognac Cedex, France, aprida@seguin-moreau.fr BY Correlation between wood extractives and sensory perception in oak-aged wines 62 Managing nutrition of wine bacteria to minimize the effect of inhibitors, PART II By Magali Déléris-Bou, Sibylle Krieger-Weber, Ph.D., and Goran Milanov, Ph.D. 65 Search for Zinfandel genetic diversity By Michael Penn, Michael Anderson, Jim Wolpert and Andrew Walker 70 Book Excerpt: Understanding Vineyard Soils, Second Edition By Robert E. White T E C H N I C A L R E S O U R C E F O R G R O W E R S & W I N E R I E S Don Neel, Editor practicalwinerylibrary.com Access Practical Winery & Vineyard article archives online.