|Suppliers of barrels with Water Immersion coopering
|Keystone Cooperage (West Coast sales: Pickering Winery Supply)
||Cabernet Sauvignon, Cabernet Franc, Chambourcin, Merlot, Syrah, Zinfandel
|Premier Wine Cask/Barrel Associates, Dargaud & Jaegle
|Seguin Moreau Napa Cooperage/Aquaflex barrels
||Chardonnay, Pinot Noir
||Cabernet Sauvignon, Petite Sirah, Zinfandel, Sauvignon Blanc
|T.W. Boswell / Eau barrels
||Chardonnay, Pinot Noir, Cabernet Sauvignon
For example, the occurrence of oaky descriptors in both parts of Table III means that the
oaky descriptor was significantly more intense for traditional process in 10 tasting sessions
during the entire study, whereas it was more intense for water-immersion in one tasting session.
The probability calculated reveals that 10 uses for the first case is an indicator of systematic
difference, while one single use for the second case is not.
Key: * = panel 1 by default. “
” = intensity of the descriptor was higher following heating by immersion; “
” = intensity of the descriptor was higher for the traditional process.
• lactones (trans- and cis-whisky-lactones) – class of compounds characterized by coconut and woody odors in pure state.
Under the reducing conditions in wine, furfural tends to be converted into furfural alcohol, so the “total furfural” content was calculated (combined concentrations of furfural and furfural alcohol).
These analyses were carried out at regular intervals, as shown in Table 1.
Preliminary studies had revealed that the wine matrix (variety, wine composition, and use of barrel such as presence of lees, oxygen, etc.) played an important role in determining the concentration of substances extracted from the oak.5 Consequently, it was not possible to apply the standard Student’s T-test to assess the difference in impact between the “traditional” and “immersion” processes.
The Student’s T-test for paired samples (immersion compared to traditional process) was used. The difference between the concentration of molecules released by oak wood in the two types of barrels was calculated for each type of wine. This test, to determine whether the average of these differences was significantly different from 0, consisted of comparing pairs of samples taken from the same wines aged in barrels produced by bending following immersion and the traditional process.
Sensory analysis of wines
Descriptors with significant differences in intensity (risk
threshold less than 5%) are presented in Table II. The “+”
sign indicates that the intensity of the descriptor was higher
following heating by immersion and the “-” sign that it was
higher in the control (fire bending).
One can observe a lack of agreement between panels I and II for wine-1, 2, 3, for some common descriptors found (toasty for wine -1 and sawdust for wine -2). The only wine where students and staff had similar findings was Wine-8. This fact shows the different perception of sensory differences between wines analysed by each panel. That is why the analysis of all of the study data is required in order to establish a common and rigorous conclusion.
Certain descriptors were used very frequently in different tasting sessions to describe various wines. This led to the assumption that heating by immersion produced systematic differences compared to the controls, irrespective of the type of wine or the period when it was tasted by the tasting panel.
To verify this hypothesis, the probability of the significant differences for each descriptor used for all the wines studied were calculated, assuming that the probability that the significant differences for each descriptor given in a specific case (wine X tasting) was 5%, to reflect the risk threshold of 5% chosen
for the sensory analyses. The other assumption was the independence of the events (tasting sessions). The results are in Table III.
Table III shows the frequency of use of descriptors where intensities were higher:
• for fire bending (fire bending line)
• for water bending (water bending line).