Different extraction methods to produce antioxidants from agro-industrial wastes

This study investigated different extraction techniques for production of antioxi-dants from chestnut shells (CS), a solid waste produced by the chestnut peeling process. Con-ventional and pressurized liquid extractions, ultrasound and microwave-assisted extractions were tested in presence of water as solvent, and the effect of the extraction time and CS concen-trations were examined. The most efficient method was pressurized liquid extraction. The high-est yields of antioxidant species, expressed in mg/mL of extract, were obtained for 10% CS af-ter 60 min of incubation: 0.836±0.018 for total phenols, 0.297±0.003 for ortho-diphenols, 0.173±0.002 for flavonoids and 0.545±0.018 for tannins. Measurement of the radical scaveng-ing activity indicated that all the extracts exhibited an antioxidant power stronger than that showed by commonly used antioxidants. HPLC analysis revealed only quantitative differences among the extracts, and gallic acid was the main simple phenol detected independently of the extraction method used. Its amount ranged from 159.66±0.31 to 284.14±0.72 microg/mL extract.