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February 2015 practical winery & vineyard 65 w i n e m a k i n g shown that the more staves are used, more SO 2 must be added in order to maintain the free SO 2 at its initial level (Figure 7). We analyzed an olfactory marker for oxidation of red wines: 3-methyl-2,4-non- anedione (MND), whose odor is remi- niscent of prune. The analysis in Figure 7 shows that its concentration increases significantly with reduction in free SO 2 in the trial at 10 g/L. However, sensory analysis of these wines does not show the appearance of oxidation faults. This result is not surprising given that the concentrations found in our trials remain below the perception threshold in wine, which is 62 ng/L. Conclusion All results obtained during this study clearly show that oak used in the form of staves is likely to supply oxygen to wines quickly and in large quantity. This result runs counter to the common idea that élevage in the presence of barrel alternatives is reductive-type maturation compared to oxidative-type maturation occurring in traditional barrels. The benefits associated with a moder- ate supply of oxygen during élevage of wine are understood: limitation of reduc- increasing concentrations of French oak staves (Oenostave, Seguin Moreau; 950 cm x 5 cm x 18 mm; medium toast) at the following rates: T2 = 5 g/L, T3 = 8 g/L and T4 = 10 g/L of oak). Under experi- mental conditions, the level of free SO 2 was adjusted each month so that the con- centration was the same for all samples (target free SO 2 = 30 mg/L) during five months of élevage. At the end of this experiment we have tive aromas, stabilization of color in red wines and a refined wine taste. Meanwhile, given the large amount of oxygen supplied by staves, the use of alternatives requires careful monitoring of the free SO 2 level by the winemaker, at the risk of development of oxidative phenomena and, in certain specific cases, the development of spoilage microflora (Brettanomyces D.; Acetobacter sp.). In practical terms, a winemaker should anticipate the loss of SO 2 caused by addi- tion of barrel alternatives to a wine. This loss is dependent on quantity of oak used and its form (chips, powder or staves), the maximum theoretical loss of free SO 2 being possible to reach 0.75 mg/L per gram of oak added. The winemaker should also consider the quantity of oxygen introduced by barrel alternatives in total oxygen bal- ance of the process. That could be impor- tant, for example, for adjusting micro-oxygenation rates used for wine production. PWV Acknowledgments The authors would like to thank Richard Nadal (winemaker from Domaine de Marsalet) and Cyril Fourcade (consultant enologist) for setting up the trials. 7 6 5 4 3 2 1 0 SO 2 (g/HL) MND (ng/L) MND SO 2 added during aging 60 50 40 30 20 10 0 Control 5 g/L 8 g/L 10 g/L Figure 7: Total quantity of SO 2 added to the wine after five months of aging in tank (50 HL) in order to maintain the free SO 2 at 30 mg/L, and the concentration of MND in the wine according to the quantity of staves. Napa Fermentation Supplies is proud to be a West Coast Kärcher distributor since 1989. Our prices are the lowest and we have the complete product line available. We are also a Kärcher repair facility. Kärcher state-of-the-art high-pressure washers are distinguished by infinitely variable operating pressure, water volume and temperature control, as well as precise chemical metering. Heated models incorporate a 90%+ fuel efficient burner system, low fuel shut-off and complete machine shut-off at the trigger gun for maximum safety and performance. NAPA FERMENTATION SUPPLIES Napa Fermentation Supplies (707) 255-6372 • napafermentation.com