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60 WINES&VINES December 2015 WINEMAKING PRACTICAL WINERY & VINEYARD atmospheric oxygen incorporated during bar- rel topping. 3 V. Vivas and G. Glories measured the sulfate concentrations formed within barrels filled with a 500 mg/L solution of sulfur dioxide, allowing them to quantify oxygen entry after six months of élevage. 2 Data from these authors indicated that the rate of oxygen entry into new barrels was greater than the rate of oxy- gen entry into used barrels. In addition, the rate of oxygen entry de- pends on the type of oak and the position of the bung. They found oxygen entry rates of 10 mg/L per year for two used French oak barrels and 28 mg/L per year for two new barrels from central France. Regarding bung position, the authors found that if the bung is closed without sealing, the annual rate of oxygen entry is 28 mg/L per year. In contrast, if the bung is closed with the traditional technique, with the bung- hole on the side, the rate of oxygen entry is 36 mg/L per year. Furthermore, if the bunghole is sealed with a silicone bung to ensure an airtight seal, the rate of oxygen entry is 45 mg/L per year. The authors determined that 21% of total oxygen entered through the bunghole, 63% of oxygen entered between the staves, and 16% of oxy- gen entered through the wood itself. This re- sult was made possible by performing the study in two barrels that were sealed differently for individual quantification. 2 Oxygen transfer rate For our study, there were 12 new Bordeaux (225 liter) barrels comprising both French and American oak that were either fine or medium grain with medium toast level. The American oak barrels were from Tonelería Victoria (Spain) and the French oak barrels from coo- perage Radoux (France). The daily increase of oxygen within each barrel was determined by considering the mean values that were ob- tained from two optical probes installed in each barrel through a silicone bung. The position of the probes in the barrel—in the lower half and at the top (156 mm and 468 mm from the bung)—was determined in the first part of this study, in which eight probes were immersed at various depths in a barrel. Readings from the probes showed that dis- solved-oxygen (DO) concentrations decreased as the distance from the bung increased. The two submergible oxygen probes (PSt6 sensor, detection limit = 0.001 mg/L, PreSens GmbH, Germany) used for the next stage of the study were chosen after being assessed as being representative of the evolution of DO within an entire barrel. All trials were carried out in a cellar with controlled temperature and humidity (15º to 16º C and 70% to 80% relative humidity). The possible temperature gradient inside the bar- rels was checked, but there was no difference within the liquid inside the barrel. Daily values from the two probes were added to determine the cumulative concentra- tions of dissolved oxygen that reached the model wine in each barrel for each day of the test. It was important to use a non-oxygen scavenger liquid with the same pH and ethanol content as wine that allows for oxygen mass balance calculations. By using a model wine (pure water and ethanol at 15% v/v, 3.5 pH), we were able to calculate the exact OTR in each barrel because there were no compounds to consume the oxy- gen. We evaluated the oxygen reaching the liquid, if wood phenolic reaction with oxygen in the wood really blocks oxygen transfer (our actual measurement suggests the opposite). During wine élevage the same effect occurs as well, therefore we evaluated the oxygen reach- ing the wine inside the barrel through the oak considering oak wood phenolics. The potential roles that the compounds in wood would have in oxygen consumption were considered in these trials, 5,6 allowing for deter- mination of the true OTR of wine barrels. That is, the amount of oxygen that would receive YOUR GATEWAY TO TEXAS Texas Wine And Grape Growers Association 2016 Annual Conference And Trade Show http://www.txwines.org/annual-conference/ February 18-20, 2016 Embassy Suites Hotel & Conference Center 7600 John Q. Hammons Drive, Frisco, Tx • Over 35 Hours Of Educational Sessions • 112 Trade Show Exhibitors • 13 Exhibit Hall Hours • Networking With Texas Wineries And Growers • Texas Size Wine Tastings Contact Office@Twgga.org or 817-41-3201