Influence of yeast strains on sensory properties and composition of volatile compounds of Pošip wine : diploma thesis

Pošip je bijela sorta grožđa koja se uglavnom uzgaja na južnim dijelovima otoka Korčule, osobito na području Čare i Smokvice gdje daje vino vrhunske kvalitete čemu svjedoče brojne nagrade i priznanja. Vino je osebujnog okusa sa svojstvenim aromama suhih marelica i smokava, blistavo, slamnate- zlatnožute boje. U posljednje vrijeme proizvođači rade brojne eksperimente kako bi utvrdili optimalne uvjete za provedbu fermentacije i odabrali odgovarajući soj kvasaca kojima bi se postigao maksimum sortnih i sekundarnih aroma i u konačnici visokokvalitetan proizvod. U ovom radu su korištena dva vina sorte Pošip koja su proizvedena s različitim kvascima. Za određivanje razlike utjecaja različitih sojeva kvasaca provedena je senzorska analiza i izolacija hlapljivih organskih spojeva mikroekstrakcijom vršnih para na krutoj fazi (HS-SPME). Aromatični profil uzoraka vina Pošip određen je vezanim sustavom plinska kromatografija-spektrometrija masa (GC -MS). Najveći intenziteti mirisnih i okusnih obilježja u vinima su bili „voćno“ i „cvjetno“. Uzorak X-16 imao je nešto veće intenzitete „voćnosti“ dok su „cvjetni“ intenziteti bili viši u uzorku X-5. Najzastupljeniji spojevi u oba uzorka vina su spojevi sekundarne arome. U skupini estera dominiraju etilni esteri viših masnih kiselina (2-metilbutil-oktanoat, etil-heksadekanoat, etil-dec-9-enoat, etil-tetradekanoat, etil-linoleat). Najviši udio u oba uzorka vina imao je ester 2-metilbutil-oktanoat čiji je senzorski opis „voćno“. U uzorku X-16 utvrđen je viši udio izoamil-acetata što se može dovesti u korelaciju s rezultatima senzorske analize gdje su obilježja „voćnosti“ viših intenziteta u uzorku X-16. Dobiveni rezultati pokazuju kako različiti kvasci različito doprinose aromi vina.Pošip is a white grape variety that is mainly grown in the southern parts of the island of Korčula, especially in the area of Čara and Smokvica, where it produces top quality wine, as evidenced by numerous awards. The wine has a distinctive taste with its aromas of dried apricots and figs, bright, straw-golden yellow in color. Recently, producers have been conducting numerous experiments to determine the optimal conditions for fermentations and to select the appropriate yeast strain that would achieve the maximum of sorted and secondary aromas and ultimately a high quality product. In this paper, two Pošip wines produced with different yeast strains were used. To determine the influence of different yeast strains, sensory analysis and isolation of volatile organic compounds by headspace solid phase microextraction (HS-SPME) were performed. The aromatic profile of Pošip wine samples was determined by the coupled gas chromatography-mass spectrometry (GC -MS) system. The highest intensities of fragrant and tasty attributes in the wines were "fruity" and "floral". The X-16 sample had slightly higher “fruitiness” intensities while the “floral” intensities were higher in the X-5 sample. The most common compounds in both wine samples are secondary aroma compounds. The group of esters is dominated by ethyl esters of higher fatty acids (2-methylbutyl octanoate, ethyl hexadecanoate, ethyl-dec- 9-enoate, ethyl tetradecanoate, ethyl linoleate). The highest share in both wine samples had the ester 2- methylbutyl octanoate, whose sensory description is "fruity". A higher content of isoamyl acetate was found in the X-16 sample, which can be correlated with the results of sensory analyzes where the "fruitiness" of higher intensities in the X-16 sample was marked. The obtained results showed how different yeast strains contribute differently to the aroma of wine