Evaluation of Polyphenols and Antioxidant Activity of Coffee and Coffee Beverages

Abstract

Coffee is one of the most popular beverages. Beside caffeine as bioactive ingredient other nutritional-physiological active compounds may contribute to the valuable properties of coffee beverages. Coffee has been identified as a rich source of polyphenols which are well-known for their antioxidant properties and health benefits. Green and roasted coffee beans from different origins (Coffea Arabica from Nicaragua, Brazil and Ethiopia and Coffea Robusta from Ecuador) as well as coffee beverages prepared by commonly used procedures as espresso and filter coffee were analyzed in regard to their content of polyphenols and their antioxidant properties. Total polyphenols were determined using the Folin-Ciocalteu assay. Antioxidant activities were determined with the DPPH* radical scavenging method as well as with the ABTS-radical assay in terms of their Trolox Equivalent Antioxidant Capacity TEAC. In the different coffee beans and coffee beverages the content of total polyphenols was determined in the range of 39,6 to 55,8 mg/g with the highest amounts in Robusta coffee from Ecuador followed by the Arabicas in the order Ethiopia, Nicaragua and Brazil. The same trend was observed with the corresponding coffee beverages with higher amounts in espresso (32,6 - 39,7 mg/g) than in filter coffee (26,4 - 29,2 mg/g). All the coffee beans and coffee beverages possessed high antioxidant capacity in the same order and in correlation to the content of polyphenol compounds with TEAC-values of 0,15 - 0,41 mmol TE/g. In conclusion the highest antioxidant activity was observed in Robusta from Ecuador, green coffee beans showed higher antioxidant activity than roasted coffee beans and espresso better radical scavenging capacity than filter coffee. The results of this study indicate that coffee beverages have high antioxidant and radical scavenging properties in correlation with the content of polyphenols and are a good source of dietary antioxidants.