engleski

Influence of Temperature and Drying Duration on Extraction Yield of Phenolic Compounds from Grape Pomace Variety ˝Portogizac˝

The aim of this work was to investigate the influence of drying temperatures and duration of drying on extraction yield of phenolic compounds (total phenolic compounds, TPC ; total extractible proanthocyanidins, TPA ; total flavonoids, TF) as well as on antioxidant activity (AA) of grape pomace extracts. Drying was performed in a fluidized bed drier at different temperatures (60 °C, 70 °C and 80 °C) during 90 min, 135 min and 180 min. Extractions of phenolic compounds were performed from undried and dried grape pomace at 80 °C using 50% of aqueous ethanol solution during 120 min. Grape pomace extracts were analysed spectrophotometrically using Folin-Ciocalteu micro-method at 765 nm [1], method based on acid hydrolysis and formation of red colour at 540 nm [2], and the aluminium chloride colorimetric assay at 510 nm [3], for TPC, TPA and TF, respectively. AA of extract were evaluated by spectrophotometric method at 515 nm against stable 2.2 diphenil-1-picrylhydrazyl radical (DPPH•) [4]. Content of phenolic compounds and antioxidant activity of extracts obtained from undried grape pomace were 73.83 mgGAE/gdb, 30.53 mg/gdb, 42.24 mgCE/gdb, and 0.35 ginhDPPH/gdb for TPC, TPA, TF and AA, respectively. Drying temperature and time influenced the content phenolic compounds and results for extracts obtained from dried grape pomace compounds were lower up to 13.2 %, 43.1 %, 15.3 % and 21.0 % for TPC, TPA, TF and AA, respectively.

grape pomace ; drying ; phenolic compounds

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