Oxidation of Wines. I. Young White Wines Periodically Exposed to Air

Chardonnay and Sauvignon blanc dry white table wines and a dry sherry from French Colombard plus Thompson Seedless were bottled in screw capped bottles holding 750 ml of wine with 25.0 ml of headspace and stored at 23.5°C (75°F). At weekly intervals the headspace air was replaced with the result that the wine was exposed to about 7 ml of oxygen per liter each week. Analyses of samples covering 10-12 weeks and oxygen exposure of 0 to 80 ml per liter were made. As oxygen exposure increased, fruitiness sensory rating and general quality decreased (for sherry it increased) and oxidation flavor rating increased. Pinking and browning spectral changes are discussed. Total phenol decreased 10-14 mg gallic acid equivalents per liter in 10 weeks exposure to oxygen and this decrease involved primarily the nonflavonoid components — not the flavonoids. Vicinal dihydroxyphenols accounted for only 27-54% of the total phenols oxidized in 10 weeks. Although decrease in total oxygen capacity as measured by uptake under alkaline conditions was only of the order of 4-6 ml over a 10-week exposure to oxygen, total exposure to 60 ml of O 2 /l or so appears to be required to make the transition from table wine to sherry. Exposure to zero oxidation appears best for young white table wine quality although some indication of quality regeneration presumably with increased complexity at about 24 ml O 2 /l exposure was found with the Sauvignon blanc samples.