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64 practical winery & vineyard February 2015 w i n e m a k i n g 15 g/L, one-half of the initial free SO 2 had been consumed after 32 days of maceration. This significant decrease demonstrates the presence of pronounced oxidation phe- nomena. This result can be explained by two simultaneous phe- nomena. The first corresponds to what we just described, namely the greater supply of oxygen according to the amount of wood used. The second is a result of the disso- lution of oak wood extractives that may catalyze oxidation reactions. 13 This effect can also be observed at a rate of 5 g/L, close to that used in practice, although to a lesser extent. It is well-known that the level of ethanol in the medium plays an important role in the extractability of volatile and non-volatile compounds from oak. We have assessed the effect of alcohol content of the model medium con- taining 10 g/L of oak chips on the change in free SO 2 . In the range of ethanol concen- trations in wine, and under our experimental conditions, its presence does not increase oxidation phenomena and therefore has a negligible effect on the change in the free SO 2 level. Validation of these observations in winery: Red wine élevage The trials were performed on a 2012 Merlot wine from the Bergerac appellation. After malolactic fermentation, the wine was racked, sulfured (initial free SO 2 = 29 mg/L) and then divided into four 50H L stainless-steel tanks. The control wine (with- out staves) was monitored and three tanks treated with 35 30 25 20 15 10 5 0 0 3 6 9 15 18 30 Free [SO 2 ] mg/L Days 12% g/L 13% g/L 14% g/L 15% g/L Figure 6: Impact of the increasing alcohol concentration (% volume) on the change in the level of free SO 2 in a model wine solution supplemented with oak chips (10 g/L) (n = 3). 35 30 25 20 15 10 5 0 0 3 6 9 12 17 20 32 Free [SO 2 ] mg/L Days 0 g/L 5 g/L 10 g/L 15 g/L Figure 5: Impact of the addition of increasing quantities of oak chips on the change in the level of free SO 2 in a model solution similar to wine (n = 3). Celebrating Over 35 Years of Serving the Wine Industry Premium French, American & Eastern European Oak Barrels French Oak Alternatives Tel: (707) 257-3582 sales@bouchardcooperages.com www.bouchardcooperages.com Contact: Yannick Rousseau Tel: (707) 332 4524 • Fax: (707) 224 8734 Email: yannickrousseau@sbcglobal.net Website: www.tonnellerie-de-jarnac-16.com Handcrafted & Authentic TonnellerieDeJarnac_Dir10 11/11/09 3:40 PM Page 1 Custom made - Handcrafted Barrels