Antioxidant activity of polyphenol-enriched apple juice

Abstract

This paper shows that it is possible to improve antioxidant activity of apple juice by extraction of polyphenolic compounds from apple pomace, as waste, and their addition to the apple juice. Raw apple juice was prepared by pressing of apple mash. After thermal treatment of raw apple juice, depectinisation, additional clarification and filtration, the clarified juice was obtained. In raw and clarified apple juice soluble solids, acidity, reducing sugar, total sugars and brown component content were determined, as well as total dry matter, ash, acidity, reducing sugar, total sugars, total pectins, cellulose and starch content in apple mash and pomace. The total cotent of phenolics in clarified apple juice and apple pomace extract, determined spectrophotometrically using the Folin- Ciocalteu reagent, was 0.496 mg/ml and 6.505 mg/g, respectively. The antioxidant activity of clarified and polyphenol-enriched clarified juice (with addition of apple pomace extract in the concentrations 0.05 g, 0.1 g, 0.5 g and 1 g of phenolic compounds per liter of clarified apple juice) was examined on stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals. Based on the obtained results it can be concluded that polyphenol-enriched clarified juice was more effective on DPPH radicals than the clarified apple juice.U ovom radu ispitana je mogucnost poboljsanja antioksidativne aktivnosti soka od jabuka dodatkom polifenolnih jedinjenja ekstrahovanih iz tropa, sporednog proizvoda nastalog prilikom dobijanja soka od jabuka. Maticni sok je proizveden standardnim postupkom proizvodnje - presovanjem kase od jabuka. Nakon termicke obrade maticnog soka, depektinizacije, bistrenja i filtriranja dobijen je bistri sok. U maticnom i bistrom soku odredjen je sadrzaj kiselina, suve materije, secera i smedje komponente. Takodje, odredjen je sadrzaj suve materije, kiselina, secera, skroba, celuloze, pektina i pepela u kasi i tropu jabuka. Sadrzaj ukupnih polifenolnih jedinjenja u bistrom soku od jabuka i ekstraktu tropa, odredjen spektrofotometrijski, metodom po Folin-Ciocalteu, iznosi 0.496 mg/ml i 6.505 mg/g. Antioksidativna aktivnost bistrog soka, kao i bistrog soka od jabuka obogacenog polifenolnim jedinjenjima (sa dodatkom ekstrakta tropa u koncentracijama 0.05g, 0.1g, 0.5g i 1g polifenolnih jedinjenja po 1l bistrog soka) ispitana je na stabilne 1,1-difenil-2-pikrilhidrazil (DPPH) radikale. Obogaceni sok od jabuka pokazao je izrazeniju antioksidativnu aktivnost na DPPH radikale od soka bez dodatka ekstrakta tropa.