Phenol content and antioxidative activity of must and wine Malvasia istriana

Ovaj rad opisuje ovisnost fenolne strukture mošta i vina Malvazije istarske o različitim terminima berbe (rani, normalni, kasni), podlogama uzgoja (420 A i Kober 5BB) te broju pupova (20, 30 i 40). Udjel ukupnih fenola mošta i vina određivan je spektrofotometrijskom metodom prema Folin-Ciocalteu, baždaren na standard galne kiseline i izražena u mg/L ekvivalenta galne kiseline (GAE). Udjel ukupnih fenola uspoređivan je sa njihovom antioksidativnom sposobnosti koja je mjerena prema metodi DPPH (2,2-difenil-1-pikrilhidrazil) i BCB (izbjeljivanje pomoću β-karotena). Udjel pojedinih fenolnih spojeva prisutnih u moštu i vinu mjeren je HPLC metodom. Dobiveni rezultati ukazuju da je obzirom na fenolni udjel za uzgoj grožđa sorte Malvazija istarska najpogodnija podloga Kobber 5BB sa 30 ostavljenih pupova. Glavninu udjela određivanih fenolnih spojeva mošta i vina činili su (+)-katehin i (-)-epikatehin, dok su uz njih kod mošta značajniji udio imale hidroksibenzojeve kiseline (protokatehinska i galna), a kod vina hidroksicimetne kiseline (kava i p-kumarinska).This study describes phenol structure of must and wine Malvasia istriana depending on different term of harvest (early, regular, late) rootstocks (420 A and Kober 5BB) and bud load per vine (20, 30 and 40 buds). Total phenol concentration of must and wine samples was determined spectrophotometrically according to the Folin-Ciocalteu method, calibrating against gallic acid standards and expressing results as mg/L gallic acid equivalent (GAE). Content of total phenols was compared with their antioxidant activity measured with two different methods: DPPH (2,2-diphenyl-1-picrylhydrazyl) and the BCB (β-carotene bleaching). Concentartion of some phenol compounds in must and wine was measured by HPLC method. The obtained results indicated that regarding phenols content the rootstock Kober 5BB appeared to be more suitable for growing Malvasia istriana grape, with reference to the number of shoots developing from the real bud load of 30 buds per vine. The main phenolic content of must and wine are (+)-catechin and (-)-epicatechin while along with them in must significant quanitity makes hydroxybenzoic acids (protocatechuic and gallic) and in the wine is higer quantity of hydroxycinamic acids (caffeic and p-coumaric)