| Popis: |
Les auteurs étudient la clarification des vins en flux tangentiel avec un ultrafiltre pilote muni de membranes organiques. Les débits de perméat sont faibles (30 l x h-1 x m-2) mais le colmatage peu important. Les pourcentages de retentat sont peu élevés (0,3 à 0,7 %). Les produits ainsi clarifiés présentent de faibles turbidités et des indices de colmatage très bas. Cette technique entraîne une rétention importante des polysaccharides et des composés phénoliques des vins rouges. Les qualités organoleptiques sont légèrement affectées dans les premiers mois qui suivent l'opération, mais les différences entre les vins témoins et ultrafiltrés sont difficiles à détecter après douze mois de conservation des échantillons.+++Wine clarification with a tangentiel flux through a pilot ultrafilter with organic pads (breaking point 50,000 Daltons.) has been studied. Porosity is low (30 l x h-1 x m-2), but the blockage of the filter is hardly possible as the percentage of retentiveness is limited (0.3 % to 0.7 %). The finished wines thus clarified have a perfect sparkling clarity and a low blockage potential. The type of sterilization, however, used with this type of filter-pads made it impossible to obtain a complete erradication of all microorganisms in the filtrate. Close filtration has little influence on the aromatic flavours and aromas of white wines although macromolecules are highly affected. A 76 % to 88 % fall in the amount of polysaccharides may be observed. In the same way the phenolic compounds in red wines are affected. The more mature, the richer in alcohol and colour the wine is, the greater the effect of close filtration upon the wine; this may provoke a visible fall in the colour intensity. Close filtration improves tartric stability but has hardly any effect at all on protein stability in white wines. When applied to young wines, close filtration does not show a significant change in the organoleptic analysis compared to more traditional filtration processes, particularly when tasted after a six months period of ageing. When close filtration is applied to more mature wines, the organoleptic analysis may detect it during the first months after the filtration, but it tends to disappear and it is hardly traceable after a year or two. It is surprising to note that on such red wines the organoleptic analysis cannot detect the differences between two samples, one which had undergone close filtration and one which had not, despite a major changes in the chemical analysis particulary concerning the colour and the amount of polysaccharides. |
