DURING MATURATION OF WINES ON LEES

Traditional enological practices (« Bâtonnage » or « microoxygenation » techniques) during wine aging on yeast lees include limited repetitive additions of small amounts of oxygen to the wines. Such empirical practices are generally associated with a limited homogenisation of wine and lees. In this study, the potential relationship between oxygen consumption and the presence of wine lees during wine aging was investigated. Strong oxygen uptake rates by yeast lees were observed during wine aging at 14°C on total yeast lees obtained after fermentation of either synthetic medium or red and white grape musts. These specific oxygen utilization rates by yeast lees is always comprised between 3 and 11 µg O2 h -1 10 -9 cells from the second to the sixth month of aging. The initial levels of specific oxygen utilization rates and the time-decay of these rates along wine aging were very dependent on yeast strains. However such oxygen utilization rates by yeast lees could be responsible for the total dissolved oxygen depletion from wines in less than 20 hours at 14°C during aging on total lees. Such results were of parti- cular importance to evaluate the exact timing of oxygen additions during wine aging on lees. Further experiments had to be done to determine the biological or chemical nature of such oxygen consumption by lees. Such oxygen consumption by yeast lees may lead to final reaction products which may exert strong organoleptic effects on the final quality of wines.