Ordinary oxygen from the air is one of the many chemical factors that can affect the taste of aging wine, leading to an oenophile’s joy or despair. A study now shows for the first time that it’s possible to continuously monitor the O2 transfer rate and dissolved O2 level in oak wine barrels (J. Agric. Food Chem. 2014, DOI: 10.1021/jf502333d). The analytical technique may allow enologists to probe the mechanisms by which the gas enters casks and modulates the flavors of the aging wine. María del Alamo-Sanza and Ignacio Nevares at the University of Valladolid, in Spain, inserted commercial optical dissolved O2 probes into both American and French oak wine barrels filled with a “model” wine solution of 15% ethanol. Scientists had previously measured O2 levels in aging wine but only at a single time point of six months. The researchers in the new study used the probes to monitor O2 continuously over a year at specific locations in the barrels. The researchers found that half of the O2 that entered the barrels did so during the first two months and that O2 transfer rates into the barrels leveled off over time.