Optimisation of antioxidant activity of grape cane extracts using response surface methodology

Solid-liquid extraction and response surface methodology were used to optimise conditions for the antioxidant activity of grape cane extracts. The independent processing variables were ethanol concentration, temperature and solvent to solid ratio. Ethanol concentration and temperature significantly affected antioxidant activity measured by the Trolox equivalent antioxidant capacity (TEAC) assay and the oxygen radical absorbance capacity using fluorescein (ORAC(FL)) method (p <= 0.01), whereas the solvent to solid ratio did not significantly affect the activity (p > 0.05). Antioxidant activity of the extracts, determined by the TEAC assay, varied from 85.6 to 238.6 mu mol Trolox equivalents/g of dry sample. ORAC(FL) values ranged from 308.4 to 1302.7 mu mol Trolox equivalents/g of dry sample. Ethanol concentrations of 40.4% and 55.4% were optimal for the highest antioxidant activities measured by the TEAC assay and the ORAC(FL) method, respectively. The optimal temperature was 83.6 degrees C. Antioxidant activity correlates with total phenolic content of extracts. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.