RESUMO
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 24.5micromol Trolox/g cells (fresh weight) by the DPPH assay, and 21.3micromol 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.
Assuntos
Antioxidantes/metabolismo , Parede Celular/química , Flavonoides/metabolismo , Fenóis/metabolismo , Compostos de Sulfidrila/metabolismo , Vitis/química , Vinho/microbiologia , Leveduras/química , Compostos de Bifenilo/metabolismo , Cromanos/metabolismo , Cromanos/farmacologia , Recuperação de Fluorescência Após Fotodegradação , Microbiologia de Alimentos , Mananas/metabolismo , Mananas/farmacologia , Picratos/metabolismo , Polifenóis , Leveduras/ultraestruturaRESUMO
36 semi-industrial fermentations were carried out with 6 different yeast strains in order to assess differences in the wines' chemical and volatile profile. Two of the tested strains (Y3 and Y6) showed the fastest fermentation rates throughout 3 harvests and on 2 grape varieties. The wines fermented by three of the tested strains (Y5, Y3 and Y4) stand out for their high amounts of esters and possessed the highest fruity character. Wines from strains producing low amounts of esters and high concentrations of medium chain fatty acids, higher alcohols and six-carbon alcohols were the least appreciated at the sensory analysis. The data obtained in the present study show how the yeast strain quantitatively affects the final chemical and volatile composition of cava base wines and have repercussions on their sensory profile, independently of must variety and harvest year.
