High Antioxidant Activity of Coffee Silverskin

18 Coffee silverskin (CS) is a thin tegument of the outer layer of green coffee beans and a major 19 by-product of the roasting process to produce roasted coffee beans. CS extracts obtained by the 20 treatment of CS with subcritical water at 25–270 o C were investigated on their antioxidant 21 activity using hydrophilic oxygen radical absorption capacity (H-ORAC) and DPPH radical 22 scavenging capacity assays. The antioxidant activity increased with increasing the extraction 23 temperature and the highest activity was observed with the extracts obtained at 270 o C. The H-24 ORAC and DPPH values of the extracts were 2629 ± 193 and 379 ± 36 mol TE/g of CS extract, 25 respectively. High correlation (R = 0.999) was observed between H-ORAC and DPPH values for 26 the CS extracts. High correlation of the antioxidant activity was also observed with protein and 27 phenolic contents in the extracts. The CS extracts could be useful as a good source of 28 antioxidative materials.