Pulverization of Coffee Silverskin Extract as a Source of Antioxidant

Coffee silverskin (CS) is waste from coffee roasting process that has a value as source of antioxidant. In this research, two types of variant coffee Robusta and Arabica CS were extracted for their phenolic content, flavonoid content, and antioxidant activity. The extraction was done at 40ºC for 60 minutes using hydroalcoholic solvent. The phenolic and flavonoid content of Robusta CS extract were 816.75 ± 63.24 mg GAE/L and 32.82 ± 2.47 mg QE/L, and antioxidant activity with 54.80% inhibition, while for Arabica CS extract the analysis results were 473.51 ± 56.70 mg GAE/L of total phenolic content, 18.58 ± 2.47 mg QE/L of total flavonoid content, and 26.30% inhibition of antioxidant activity. CS extract was dried into powder. The effect of drying method (freeze drying and spray drying) affecting the phenolic content, flavonoid content, and antioxidant activity was evaluated. Total phenolic, total flavonoid, and IC50 value of spray dried Robusta CS extract were 134.76 mg GAE/ g powder, 4.03 mg QE/ g powder, and 2596.73 ppm respectively, while for freeze dried Robusta CS extract were 162.91 mg GAE/ g powder, 6.31 mg QE/ g powder, and 2139.80 ppm respectively.