Effect of SO2, reduced glutathione and ellagitannins on the shelf life of bottled white wines

This work studied the effect of reduced glutathione (GSH) and/or ellagitannins added at bottling on the shelf life of a white wine with a medium/low SO2 content at two levels (-SO2 and +SO2). After 3 months of bottle aging, the trials with the higher level of SO2 (+SO2) were significantly less colored, more fruity, more soft and less bitter than the corresponding trials with the lower level of SO2 (-SO2). After 6 months, the +SO2 trials were significantly distinguished from the -SO2 trials for the more intense floral and fruity notes and the less intense oxidative notes. The addition of GSH and/or ellagitannins did not extend the shelf life of bottled wines: no complementary effects of these additives to SO2 were observed. The effect of GSH was also studied at higher levels of SO2 and two different levels of dissolved oxygen. The addition of GSH caused a significant increase in the oxygen consumption rate during the first month of bottle aging, but after 1 year, no effects on the oxidation process were observed. GSH, unlike other antioxidant additives, did not increase the consumption of SO2. GSH, like SO2, can most likely react with o-quinones but, most likely, not with the hydroperoxyl radical to yield hydrogen peroxide, which causes an increase in SO2 consumption. The rapid and almost complete loss of GSH was observed during the first months of bottle aging. The possibility of using doses of GSH > 20 mg L-1 and combining enological techniques aimed at controlling the multiple causes of wine oxidation should be taken into account.