Ultrasound -assisted extraction of phenolics from grape pomace

Abstract

Grape pomace is a by-product of wineries. It is one of the most potent antioxidant sources due to its high phenolic content. In this thesis study, ultrasound – assisted extraction of phenolic compounds from grape pomace has been investigated. The effects of concentrations of solvent, extraction temperature and extraction time were studied. Folin-Ciocalteu method was used to analyze the effects of process parameters on the total phenolic content of the extracts. When fixing the extraction temperature and extraction time with 45oC and 20 minutes and concentration of ethanol was varied from 10% to 90%, the highest phenolic content was 9.23 μg FAE/mL at 90% ethanol. Moreover, the highest phenolic content was 5.87 μg FAE/mL, when extraction temperature was set from 40oC to 55oC, while ethanol concentration was 90% and the extraction time was also fixed with 20 minutes. Finally, the different levels of extraction time were set from 10 minutes to 40 minutes at 90% ethanol and 55oC of extraction temperature, the highest phenolic content was 6.14 μg FAE/mL at 40 minutes. Therefore, the highest phenolic content in the extracts (6.14 μg FAE/mL) was obtained using 90% aqueous ethanol as solvent, applying 40 minutes of extraction time and extraction temperature at 55oC. Keywords: Grape pomace, total phenolics, ultrasound, extraction.