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60 practical winery & vineyard February 2015 w i n e m a k i n g constant topping up with sulfur dioxide, he established that the transfer of oxygen through the wood was limited, amount- ing to between 2 and 5 ml of oxygen per liter per year. Almost 60 years later, N. Vivas in Bordeaux, 15 F. Feuillat in Dijon 3 and M. Moutounet in Montpellier 9 took up this research while emphasizing other aspects—particularly measurement of wood porosity—an indirect way to esti- mate the extent of gas exchange across the mass of wood. The use of barrel alternatives for aging in stainless steel tanks makes any exchange between the wine and the atmosphere impossible. But as with barrels, the high porosity of oak wood means oxygen trapped in oak pores can progressively dissolve in the wine. The first studies carried out by F. Feuillet, 2 and more recently by others, agree on the measurement of the total porosity of oak wood: 63% on average. 8 It is therefore pos- sible to estimate the maximum quantity of oxygen contained in 1 g of dry wood to be 0.4 mg. With reasonable, traditional use of staves (a rate of 8 g/L), the wine can there- fore receive a maximum theoretical supply of 3.2 mg/L of oxygen. This paper presents the first results relating to the study of oxygen supplied by staves: from development of a proto- col for measurement of extractable oxy- gen from wood to the study of the impact of using staves on oxidation markers (SO 2 and MND). Equipment and methods The samples came from 15 staves of French oak cut either into small staves of 3 cm x 5 cm x 2 cm or into chips using an industrial grinder. The samples were taken from stocks at the Seguin-Moreau cooperage. Half of the samples were toasted (medium toast) according to the cooper's protocol. Before use, the sam- ples were weighed using a precision balance. The oak samples were macerated (about 16 g/L) in an alcohol-water solu- tion previously desorbed using nitrogen ([O 2 ] final less than 50 g/L). The dissolved oxygen was measured using a PreSens sensor placed on the wall of the flask. The level of dissolved oxygen was mea- sured at regular intervals in the solution that had been prepared in a hermetically sealed flask and placed in a thermostati- cally controlled chamber. The analysis of the 3-methyl-2,4-non- anedione (MND) was performed by liq- Coarse grain Fine grain O2 max., mg/L 3,50 3,00 2,50 2,00 1,50 1,00 2A O 2 max. mg/L Figure 2A and 2B. Box-plot representation of the maximum O 2 level measured in alcohol-water solution. The vertical line corresponds to the median of the measured values. Figure 2A: Comparison of coarse and fine grain. Figure 2B: Comparison of toasted and non-toasted staves. Toasted oak Non-toasted oak 4,00 3,00 2,00 1,00 ,00 Page 1 O 2 max. mg/L 2B