title: Antioxidant Generation during Coffee Roasting: A Comparison and Interpretation from Three Complementary Assays.
abstract: Coffee is a major source of dietary antioxidants; some are present in the green bean, whereas others are generated during roasting. However, there is no single accepted analytical method for their routine determination. This paper describes the adaption of three complementary assays (Folin-Ciocalteu (FC), ABTS and ORAC) for the routine assessment of antioxidant capacity of beverages, their validation, and use for determining the antioxidant capacities of extracts from coffee beans at different stages in the roasting process. All assays showed a progressive increase in antioxidant capacity during roasting to a light roast state, consistent with the production of melanoidins having a higher antioxidant effect than the degradation of CGAs. However, the three assays gave different numbers for the total antioxidant capacity of green beans relative to gallic acid (GA), although the range of values was much smaller when chlorogenic acid (CGA) was used as reference. Therefore, although all three assays indicated that there was an increase in antioxidant activity during coffee roasting, and the large differences in responses to GA and CGA illustrate their different sensitivities to different types of antioxidant molecule.
authors.affiliation: Institute of Chemistry and Biological Chemistry, Zurich University of Applied Sciences, Einsiedlerstrasse 31, CH-8820 Wädenswil, Switzerland. opit@zhaw.ch.
authors.forename: Sebastian E W
authors.initials: SE
authors.lastname: Opitz
authors.affiliation: Institute of Chemistry and Biological Chemistry, Zurich University of Applied Sciences, Einsiedlerstrasse 31, CH-8820 Wädenswil, Switzerland. smrk@zhaw.ch.
authors.forename: Samo
authors.initials: S
authors.lastname: Smrke
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, 530004 Guangxi, China. bernard_a_goodman@yahoo.com.
authors.forename: Bernard A
authors.initials: BA
authors.lastname: Goodman
authors.affiliation: AG, Gupfenstrasse 5, 9240 Uzwil, Switzerland. marco.keller@buhlergroup.com.
authors.forename: Marco
authors.initials: M
authors.lastname: Keller
authors.affiliation: AG, Gupfenstrasse 5, 9240 Uzwil, Switzerland. stefan.schenker@buhlergroup.com.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schenker
authors.affiliation: Institute of Chemistry and Biological Chemistry, Zurich University of Applied Sciences, Einsiedlerstrasse 31, CH-8820 Wädenswil, Switzerland. yere@zhaw.ch.
authors.forename: Chahan
authors.initials: C
authors.lastname: Yeretzian
keywords: ABTS; Folin-Ciocalteu; ORAC, flow injection analysis; antioxidant assays; coffee