Polyphenol composition of grapes

Analize polifenolnog sastava su važne zbog njihovog značajnog utjecaja na boju, trpkoću, gorčinu i oksidativnu razinu. Jedino grožđe s visokim i ujednačenim razinama polifenola može dati crno vino prikladno za starenje. Cilj ovog rada bio je odrediti polifenolni sastav pokožice i sjemenke grožđa sorte Teran. Uzorci su uzimani na dvije lokacije u Vinogorju Istra i to na području Kosinožići i Motovunu, u četiri navrata tijekom dozrijevanja grožđa u razmacima od tjedan dana. Analiza je provedena primjenom spektrofotometrijskih metoda kojima je određen udio ukupnih fenola i udio ukupnih antocijana. Pokazalo se da je udio fenola u uzorcima ekstrakta pokožice sa područja Motovuna veći u odnosu na one s područja Kosinožića. U udjelu ukupnih fenola kod uzoraka ekstrakta sjemenke nema značajne razlike. Udio ukupnih antocijana se također ne razlikuje značajno između uzoraka s obje lokacije.The analysis of polyphenol composition is important because of their significant influence on color, astrigency, bitterness and antioxidative properties. It is maintained that only the grapes containing high and balanced level of polyphenols can yeld red wine which is suitable for maturing. The puropse of this work was to determine polyphenolic composition of grape skin and seeds of the Teran variety. Samples have been harvested on two locations in Istria wineyards, Kosinoţići and Motovun, in four occasions during maturation of grapes in weekly intervals. The analysis has been conducted by the use of spectrophotometryc methods to determine the content of total phenols and total anthocyans. It has been shown that the content of phenols in the samples from Motovun of extracts of grape skin is higher than in those from the location of Kosinoţići. The content of total phenols in extracts from the seeds there is no significant difference. Total anthocyan content as well doesnt show significant difference between samples from the two locations