Influence of 6 different strains of yeasts on the phenolic composition of Barbera wines obtained with delayed extraction of anthocyanins
2002
Bosso, A. (Consiglio per la Ricerca e la Sperimentazione in Agricoltura (CRA) - Istituto Sperimentale per l'Enologia, Asti (Italy)) | Guaita, M. (Consiglio per la Ricerca e la Sperimentazione in Agricoltura (CRA) - Istituto Sperimentale per l'Enologia, Asti (Italy)) | Follis, R. (Consiglio per la Ricerca e la Sperimentazione in Agricoltura (CRA) - Istituto Sperimentale per l'Enologia, Asti (Italy)) | Di Stefano, R. (Consiglio per la Ricerca e la Sperimentazione in Agricoltura (CRA) - Istituto Sperimentale per l'Enologia, Asti (Italy))
Six different strains of Saccharomyces cerevisiae, among which five were already on the market, have been studied. The aim of this work was to compare their capacity of absorption of polyphenols and their influence on wine colour, working with small amounts of must added of polyphenols. Furthermore, the influence of the different strains of yeasts on chemical and sensory characteristics of wines made from Barbera grapes has been studied. A technique, which consists in delaying the anthocyanins extraction, has been used in order to improve the colour stability of wines during ageing. As a whole, the wines obtained were of good quality and very similar between them, both for tannins content and for the colour. Particularly, at the end of sugar fermentation, the sample fermented with the experimental strain stood out for being more coloured and with higher content of pigments not decolourable by SO2. When the first sensory evaluation was carried out, this sample was evaluated significantly more coloured, more fruity and, on average, less astringent and smoother than the other ones. The control, on the contrary, at the running off, was, on average, the poorest one in tannins and anthocyanins and less coloured. From laboratory experience there is no evidence of differences between the 6 strains concerning the capacity of absorption of polyphenols and their influence on wine colour: the loss in anthocyanins is due much more to the oxidation reactions at the beginning of sugar fermentation than to the absorption by yeasts. During the conservation of wines on lees, there was no evidence of further absorption of polyphenols: as regards anthocyanins, especially the tri-hydroxylated ones (delphinin in particular), they were absorbed more during the second half of sugar fermentation. During the conservation, the anthocyanins absorbed by lees maintained their reactivity and keep evolving like wine anthocyanins
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