Effect of roasting and brewing on the antioxidant capacity of espresso brews determined by the QUENCHER procedure

This study aimed to evaluate the changes in the antioxidant capacity of coffee after roasting to several degrees, and also the corresponding espresso brews using the direct QUENCHER procedure. In addition, volumetric fractions were collected in partitions during brewing of espresso to observe the extractability of antioxidant capacity in green and roasted beans. Roasting provided a 35% increase in the Trolox equivalent antioxidant capacity after roasting at 220 degrees C for 20 min. Approximately half of the antioxidant capacity can be brewed to espresso beverage from ground coffee independent of the roasting degree. During brewing espresso, 30 mL was shown enough to get the 76% of the antioxidant activity with respect to longer extraction volumes. Extraction of 5-caffeoylquinic acid showed a similar pattern to antioxidant capacity. On dry matter basis, antioxidant capacity of the volume fractions increased both in green and roasted coffee. This indicated that the fraction having higher antioxidant capacity extracts more difficultly during espresso brewing. (C) 2016 Elsevier Ltd. All rights reserved.