Chlorogenic acids, caffeine content and antioxidant properties of green coffee extracts: influence of green coffee bean preparation

Abstract

Chlorogenic acids and caffeine are important for flavor formation as well as the health effect of green coffee brews and its extracts. The content of these compounds was determined by HPLC–DAD analysis in twelve samples of coffee from Robusta and Arabica types of different geographical origin including steamed and decaffeinated coffees. Generally, Robusta coffee extracts contain twice as much caffeine as Arabica, and its content varies from 3.41 % per dry mass in Arabica type from Laos or Rwanda to 8.16 % in Robusta coffee from Indonesia. The highest concentration of 5-O-caffeoylquinic acid (5-CQA) was obtained for both coffees from Uganda. Decaffeination process does not affect the concentration of this main chlorogenic acid, but steaming of the coffee beans with hot water produced a significant decrease in the level of 5-CQA. Antioxidant activity of coffee extracts was measured by CUPRAC and F–C assays, which really measure the reducing power of the sample components. Extracts of green coffee beans from Vietnam possessed the highest antioxidant activity in both assays.