| Abstract | U ovom radu ispitan je utjecaj temperature i vremena sušenja na udio ekstrahiranih fenolnih spojeva (ukupni fenolni spojevi, \(UFS_{_FC}\) i \(UFS_{_PB}\); ukupni flavonoidi, UF; ukupni proantocijanidini UPA) te na antioksidacijsku aktivnost (AA) ekstrakta tropa grožđa. Istraživanje je provedeno na tropu dviju sorti grožđa, Traminac i Portogizac. Sušenje je provedeno u fluidiziranom sloju na različitim temperaturama (60 ⁰C, 70 ⁰C i 80 ⁰C) tijekom 90 minuta, 135 minuta i 180 minuta. Ekstrakcija fenolnih spojeva je provedena iz vlažnog i sušenog tropa grožđa na 80 ⁰C, 50 %-tnom vodenom otopinom etanola tijekom 120 minuta na 200 rpm. Udio fenolnih spojeva i antioksidacijska aktivnost ekstrakata tropa grožđa određena je spektrofotometrijskim metodama. Udio fenolnih spojeva i antioksidacijska aktivnost ekstrakata vlažnog tropa grožđa kod sorte Traminac iznosili su 80,04 \(mg_{GAE}/g_{s.t.}\), 38,36 \(mg_{GAE}/g_{s.t.}\), 47,38 \(mg_{CE}/g_{s.t.}\), 30,74 \(mg/g_{s.t.}\), 0,43 \(g_{inhDPPH}/g_{s.t.}\) za \(UFS_{_FC}\), \(UFS_{_PB}\), UF, UPA i AA. Vrijednosti udjela fenolnih spojeva i antioksidacijska aktivnost ekstrakata sušenog tropa grožđa bile su do 32,7 % i 31,7 % više za \(UFS_{_FC}\) i \(UFS_{_PB}\) i do 16,8 %, 35,4 % i 39,5 % niže za UF, UPA i AA. Udio fenolnih spojeva i antioksidacijska aktivnost ekstrakata vlažnog tropa grožđa kod sorte Portogizac iznosili su 73,83 \(mg_{GAE}/g_{s.t.}\), 39,15 \(mg_{GAE}/g_{s.t.}\), 42,24 \(mg_{CE}/g_{s.t.}\), 30,53 mg/gs.t., 0,35 \(g_{inhDPPH}/g_{s.t.}\) za \(UFS_{_FC}\), \(UFS_{_PB}\), UF, UPA i AA. Vrijednosti udjela fenolnih spojeva i antioksidacijska aktivnost ekstrakata sušenog tropa grožđa bile su do 13,2 %, 22,3 %, 15,3 %, 43,1 % i 20 % niže za \(UFS_{_FC}\) i \(UFS_{_PB}\), UF, UPA i AA. |
| Abstract (english) | The aim of this work was to investigate the influence of temperature and drying time on some of the extracted phenolic compounds (total phenolic compounds, \(TPC_{_FC}\) and \(TPC_{_PB}\); total flavonoids, TF; total proanthocyanidins TPA) and on the antioxidant activity (AA) of grape pomace extract. The study was carried out on two grape varieties, Traminac and Portogizac. Drying was carried out in a liquefied layer at different temperatures (60 ⁰C, 70 ⁰C, 80 ⁰C) for 90 minutes, 135 minutes and 180 minutes. The extraction of phenolic compounds was carried out on moist and dry grape pomace at 80 ⁰C with a 50 % water-ethanol solution for 120 minutes at 200 rpm. The proportion of phenolic compounds and the antioxidant activity of grape pomace was determined by spectrophotometric methods. The content of phenolic compounds and antioxidant activity of wet grape pomace extract in Traminac variety were 80.04 \(mg_{GAE}/g_{db}\), 38.36 \(mg_{GAE}/g_{db}\), 47.38 \(mg_{CE}/g_{db}\), 30.74 \(mg/g_{db}\) and 0.43 \(g_{inhDPPH}/g_{db}\) for \(TPC_{_FC}\), \(TPC_{_PB}\), TF, TPA and AA, respectively. The percentage of phenolic compounds and antioxidant activity of the dry grape pomace extract was 32.7 % and 31.7 % higher for \(TPC_{_FC}\) and \(TPC_{_PB}\), and 16.8 %, 35.4 % and 39.5 lower for TF, TPA and AA, respectively. The levels of phenolic compounds and antioxidant activity of Portogizac wet grape pomace extract were 73.83 \(mg_{GAE}/g_{db}\), 39.15 \(mg_{GAE}/g_{db}\), 42.24 \(mg_{CE}/g_{db}\), 30.53 \(mg/g_{db}\) and 0.35 \(g_{inhDPPH}/g_{db}\) for \(TPC_{_FC}\), \(TPC_{_PB}\), TF, TPA and AA, respectively. The percentage of phenolic compounds and antioxidant activity of the dry grape pomace extract was 13.2 %, 22.3 %, 15.3 %, 43.1 % and 20 % lower for \(TPC_{_FC}\), \(TPC_{_PB}\), TF, TPA and AA, respectively. |
