| Abstract | Antioksidacijska aktivnost polifenola prisutnih u vinu predmet je brojnih istraživanja najviše zbog njihovog blagotvornog utjecaja na ljudsko zdravlje, ali i na organoleptička svojstva vina. U grožđu, pa tako i u vinu polifenolni spojevi su zastupljeni u dvije osnovne grupe: flavonoidi i neflavonoidi. Predstavnici flavonoida su flavonoli, flavanoli, flavan-3-oli i antocijani, a neflavonoida fenolne kiseline (hidroksibenzojeve i hidroksicimetne), te stilbeni, antocijanidi i proantocijanidi. Polifenolni sastav vina primarno ovisi o kultivaru, ali i o ampelotehničkim zahvatima u vinogradu, te o tehnologiji proizvodnje vina. Antioksidansi imaju vrlo bitnu ulogu u redukciji slobodnih radikala čime se sprječava oksidacija daljnjih važnih molekula u nizu reakcija. Međutim, jedan od glavnih problema tijekom vinifikacije je proces tamnjenja vina, koji se dijeli na enzimsko i neenzimsko, a za što su odgovorni fenoli, posebice o-difenoli. Enzimsko tamnjenje obuhvaća reakcije hidroksilacije fenola, a neenzimsko tamnjenje reakcije oksidacije i polimerizacije fenola. Sve te reakcije utječu na promjenu boje vina, pri čemu bijela vina poprimaju nepoželjnu smeđu boju, dok crvena vina postaju mekša i manje trpka. Mjerenje antioksidacijske aktivnosti temelji se na inhibiciji slobodnih radikala, kelaciji metalnih iona i lipidnoj peroksidaciji, a najčešće primjenjene metode su ORAC, DPPH i ABTS. |
| Abstract (english) | Antioxidant activity of polyphenols present in wine is the subject of numerous studies mainly due to their beneficial effects on human health, but also the organoleptic characteristics of wine. In grapes and wine polyphenolic compounds are present in two main groups: flavonoids and nonflavonoids. Representatives of flavonoids are flavonols, flavanols, flavan-3-ols and anthocyanins, and of nonflavonoids are phenolic acids (hydroxybenzoic and hydroxycinnamic), stilbenes, anthocyanidins and proanthocyanidins. Polyphenolic composition of the wines primarily depends on the cultivar, the viticultural practices in the vineyard and the wine production technology. Antioxidants play crucial role in the reduction of free radicals by which the oxidation of downstream molecules is prevented. However, one of the main problems during the vinification process is wine browning, which is divided into enzymatic and non-enzymatic, and for which the phenols, especially o-diphenols are responsible. Enzymatic browning involves the hydroxylation reaction of phenols and non-enzymic browning can arise through several reactions which includes oxidation and polymerization. All these reactions affect discolouration of wine, where white wines take on unwanted brown color, while red wines become softer and less bitter. Measurement of antioxidant activity is based on inhibition of free radicals, chelation of metal ions and lipid peroxidation, and applied methods are ORAC, DPPH and ABTS. |
