Utilizacion de sulfuro de hidrogeno y anhidrido sulfuroso en dosis parciales en la fermentacion de uvas sauvignon a dos temperaturas.

In order to obtain less content of total SO2 and acetaldehyde in wines coming from the fermentation of a Sauvignon Blanc must an experiment was carried out based on a completely aleatory design with a factorial structure 20.000. The factors were the following: two fermentation temperatures (20 and 28 deg C) two SO2 levels applied to the must before settling (0 and 50 ppm) two H2S levels applied to the settled must (0 and 10 ppm) and two SO2 levels applied at 1020 g/l density and 20 deg C. The must was clarified with a colloidal suspension of silicon dioxide combined with gelatine, and after resting for 8 hours, 70% decanted and supplemented with 15 g/Hl of selected yeast. The speed of fermentation was controlled and the wine obtained was treated with 100 ppm of SO2, filtered by a cellulose plaque and bottled before being analyzed. The results were analyzed considering the factors of the experiment, their influence on the speed of fermentation and on the physical, chemical and organoleptical characteristic of the wines. It could be established that a large amount of selected yeast on quick settling musts inhibited the development of other microorganisms, even in wines fermented at 28 deg C. The content of acetaldehyde is directly related to the amount of SO2, and this content determines the concentration of SO2 in the different states. It is possible to obtain low levels of SO2 and acetaldehyde in wines fermented at 28 deg C. Significative differences in the degree of browning were not observed, except in musts treated with H2S. Fermentation temperature of 20 deg C produced wines of a better quality than that obtained at 28 deg C. The application of 10 ppm of H2S generated wines with a strong hydrogen sulphide odor, that when treated with copper sulphide was significantly reduced, thus allowing the expression of sulphured off-flavors, with a fruit note, including those fermented at 28 deg C. The partial application of SO2 produced less content of acetaldehyde, total SO2 and combined SO2, than applying the sum of the partial dose before fermentation. In fact, it is possible, through a rational process of vinification, even with traditional systems, to obtain low levels of acetaldehydes and total sulphurs without risking the sanity and good quality of wines.