Recovery of phenolic antioxidants from the peel fraction of bilberry (Vaccinium myrtillus L.) processing waste

The extraction of phenolic compounds from the peel fraction of bilberry processing waste was investigated. The phenolic content of bilberry peels was 25.3 ± 2.4 mg GAE per gram dry weight and the flavonoid content was 2.85 ± 0.42 mg QE per gram dry weight. Extraction experiments were carried out in batch mode, using ethanol-water mixtures as solvent. A central composite design was used to study the effects of liquid-to-solid ratio (R = 20-40 mL g-1), aqueous ethanol concentration (C = 30-70 vol%), extraction time (E = 90-210 min) and temperature (T = 30-50 °C) on the recovery of phenolic compounds. Under the best conditions (R = 40 mL g-1, C = 70%, E = 210 min and T = 50 °C) over 95% of the phenolics present in the waste were recovered. R, C and T were the most influential factors and all had a positive effect on the extraction efficiency. Based on the statistical analysis of the data, a simplified model was developed which provided an accurate estimation of the extraction yields both inside and outside the design space. Overall, the results of this study strongly support the potential of bilberry processing waste as a source of natural antioxidants and give useful directions on how to improve recovery by proper selection of extraction conditions. © 2014 Trade Science Inc. - INDIA.