In vitro antioxidant activity of coffees brewed using different procedures (Italian, espresso and filter)

The possible effects of different preparation methods (Italian or Mocha, Filter and Espresso) on the antioxidant activities of brewed coffee were assessed using two methods: Ferric reducing power (FRAP) and scavenging capacity (ABTS). In addition, the polyphenol content was estimated. The order of ferric reducing ability per gram of dry matter (dm) of the different brewed coffees tested, in terms of the coffee-making procedure used, was freeze-dried > filter ≈ espresso ≈ Italian. The order of ferric reducing ability per serving was filter > espresso > freeze-dried ≈ Italian. In the case of scavenging activity the order was similar to that described for the FRAP assay. There was a high correlation between the estimated polyphenol contents and the FRAP, or the ABTS values (r: 0.98, P<0.01; r: 0.99, P<0.01, respectively). In the case of FRAP and ABTS assays; a serving of filtered coffee was equivalent to 2653 ± 297 and 1295 ± 262 μg trolox, respectively. In the USA and Northern Europe, the pot containing the coffee is usually kept hot (85 °C) for several hours. We found that antioxidant activity increased significantly (by 34%) after four hours of heating. The cause of this increase would seem to be the formation of Maillard products, due to the heat process. These compounds also appear to be responsible for the fact that antioxidant capacity was higher in dark-roast than in other brewed coffees tested. Antioxidant activity decreased when milk was added to the espresso coffee.