Copyright © 2007 Elsevier Ltd All rights reserved.
Composition and antioxidant activity of raisin extracts obtained from various solvents
Received 13 July 2007;
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Abstract
Experiments were conducted to determine if the contents of phenolics and browning reaction products and antioxidant activity of raisin extracts were closely dependent on the extraction solvent. Enhanced extraction yields were obtained from solvent containing higher water concentrations. However, total phenolic content (TPC) was highest for extracts obtained from solvent to water ratios of 60:40 (v/v), whereby the extract obtained from ethanol:water (60:40, v/v) had the highest TPC of 375 mg gallic acid equivalents (GAE)/100 g extract. HMF content was highest in extracts obtained from 60% solvent, regardless of solvent type. The extract obtained from 60% methanol had the highest HMF content at 199 μg/g extract. Although the 60% solvents provided extract with high antioxidant components, the antioxidant activity of raisin extracts obtained from 80:20 (v/v) solvent/water was significantly higher than other raisin extracts obtained from different solvent concentrations. Phenolic acids, HMF, and low-molecular-weight flavonoids were responsible for the antioxidant activity, but not the high-molecular-weight flavonoids.
Keywords: Antioxidant activity; Raisin extract; Bulk oil; Solvent extraction; HMF; Phenolic compounds
Article Outline
- 1. Introduction
- 2. Materials and methods
- 2.1. Materials
- 2.1.1. Raisin extract preparation
- 2.2. Total phenolics
- 2.3. Phenolic and HMF profile analysis by HPLC
- 2.4. Antioxidant activity evaluation
- 2.5. Statistical analysis
- 3. Results and discussion
- 3.1. Extraction yield
- 3.2. Total phenolic content
- 3.3. HMF (hydroxymethylfufural)
- 3.4. Antioxidant activity
- 3.5. Phenolic compounds
- 4. Conclusion
- Acknowledgements
- References







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