Panelists performed blind quantitative descriptive analysis using a standard list of descriptors including six odor (overall oaky, fruity, sawdust, vanilla, toasty, spicy) and five taste descriptors (acidity, bitterness, tannic intensity, structure, length). The sensory sessions were organized by series with the same wine aged in fire-bent and immersion/fire-bent barrels. The order of presentation was arbitrary and different for different panelists to obtain more objective data.

The tasting sessions were conducted in tasting rooms following the usual practices in wine tasting and were conducted by a session observer. Before the sensory analysis, the bottle was tasted in order to look for possible off-flavors and was rejected if there was an abnormal odor.

Panel members awarded 0 to 10 points according to the intensity of each descriptor (0 – very weak, 10 – very strong).

The values given by each taster were normalized using the average value for that taster over the entire series. The Independent Student’s T-test was applied to the normalized values to identify the descriptors for which there was a variation in intensity between the barrels made using “immersion” and the “traditional process.”

Only those descriptors showing differences with a probability below 5% were retained for further processing.

• furan and pyran compounds (furfural, 5-hydroxymethyl-furfural, 5-methyl-furfural, furfuryl alcohol, maltol, and ethyl maltol) – class of compounds characterized by toasty and butterscotch odors in pure state;

• aromatic aldehydes (vanillin and syringaldehyde) – class of compounds characterized by vanilla/woody odors in pure state;

• volatile phenols (guaiacol, 4-methyl-guaiacol, eugenol, isoeugenol, o-cresol, m-cresol, phenol, syringol, and allylsyringol) – class of compounds characterized by smoky, phenol and spicy odors in pure state;

Wines aged in barrels where the staves have been bent following hot water immersion are empirically perceived to be less marked by oaky aromas. However, to date, very little scientific data was available concerning the impact of this bending technique on wood/wine exchanges, thus making it impossible to explain the sensory differences noted in empirical observations.

This report presents the results of a two-year comparative study of the two stave bending techniques, focusing on the sensory profiles of wines aged in the different types of barrels and their concentrations of volatile molecules.

In the “traditional process,” raised barrels are preheated (A) for 10 to 15 minutes to a temperature of 100° to 120°C to soften the wood fibers and make them pliable. This process does not cause any major production of compounds arising from toasting; indeed,

any modifications are insignificant compared to those that occur during the toasting stage.

In the process employing bending by “immersion,” the preheating stage (A) is replaced by soaking in hot water (B). The temperature of the water does not exceed 100°C; production of toasting products due to heating are negligible.

Toasting – The heating process that causes chemical modifications in the wood was performed according to the standard “medium-long” protocol used in the cooperage. This stage was identical, irrespective of the type of bending process: heating over a fire or by immersion.