Influence of storage after membrane filtration on the chemical composition and quality of the Graševina wine sort

Zadatak rada bio je ispitati kako će skladištenje nakon membranske filtracije utjecati na kemijski sastav i kvalitetu vina sorte Graševina. Vino je filtrirano na pilot membranskom filteru. Određen je sastav filtriranog vina standardnim metodama te je prema kemijskom sastavu vino svrstano u određenu skupinu kvalitete. Tijekom skladištenja smanjio se sadržaj ukupnog i slobodnog SO2, neznatno se smanjio sadržaj ukupnih i hlapivih kiselina. Smanjila se antioksidativna vrijednost, boja i bistroća te se smanjio sadržaj flavonoida. Neznatno se povećao sadržaj etanola, pepela i pH vina. Nije došlo do značajne promjene sadržaja šećera. Značajna promjena je smanjenje sadržaja ekstrakta bez šećera i prelazak vina u nižu kategoriju kvalitete. Vino prije skladištenja je pripadalo skupini vrhunskih vina, a nakon skladištenja od 6 mjeseci pripada skupini kvalitetnih vina.The main task of this work was to examine how the storage of the wine sort Graševina after the membrane filtration will influence the chemical composition and quality of the above mentioned. The wine has been filtered on a pilot membrane filter. The composition of the filtered wine was determined by standard methods and classified into a particular quality according to the chemical compositon of the wine. During the wine filtration, the proportion of free and total SO2, as the content of total and vapourated acids decreased. Further more, the proportion of the antioxidant activity, the flavonoids, the limpidity and the intensity of colour has also decreased. On the other hand, the proportion of alcohol, ash and the pH number has slightly increased. Regarding the contretation of sugar, no significant change has been detected. A solemn alteration was the decrease of the proportion of the extract without sugar, which resulted in lower quality of the wine sort. Before the storage, the wine was rated as premium quality, and after six months it is aligned only in quality wine