Antioxidant activity of lees cell surface during sparkling wine sur lie aging

Given the importance of the interactions between wine and lees cell surface during sparkling wine aging, and in view of recent results proving the antioxidant potential of yeast cell wall biomolecules, the antioxidant capacity of lees cell surface was investigated to establish its possible role in the antioxidative effect of lees. The surface antioxidant activity of lees from wines with different aging periods was determined on the whole cell by two widely used methods (DPPH and FRAP assays), obtaining maximum values of 24.5 μmol Trolox/g cells (fresh weight) by the DPPH assay, and 21.3 μmol Trolox/g cells (fresh weight) by the FRAP assay. Lees surface antioxidant activity was influenced by base wine characteristics and inversely related to sur lie aging period. Conversely, the percentage depletion of lees surface antioxidant activity during aging was mainly determined by the length of aging, regardless of wine characteristics. To examine the influence of cell wall thiol groups and adsorbed polyphenols on lees' protective effect, their presence on cell surfaces was assessed. They accounted for 25 ± 11% and 54 ± 7% of the antioxidant activity measured by DPPH, respectively, and 0.3 ± 0.1% and 39 ± 8% measured by FRAP, respectively. Only a part of the remnant antioxidant activity of lees surface measured by FRAP could be theoretically explained by the presence of cell wall mannans.