Kinetic matching approach applied to ABTS assay for high-throughput determination of total antioxidant capacity of food products

Antioxidant data based on ABTS assay are dependent on reaction time because the applied standard compound (Trolox) presents a scavenging kinetic profile different from that of polyphenol-rich foods. Hence, in this work we propose a kinetic matching approach for ABTS assay. This methodology is based on selecting a standard compound that presents a kinetic profile similar to the sample, which provides the same antioxidant capacity independent of the selected reaction time. To demonstrate the feasibility of this approach, several food products containing different phenolics were analyzed. By selecting the appropriate standard for espresso coffees (standard phenolic mixture), green teas ((−)-epigallocatechin gallate), black teas (hesperetin), white wines (morin) and enological tannins (tannic acid), total antioxidant capacity can be determined in 5–15 min corresponding to a sample throughput of 64–192 h−1. Total antioxidant capacity values were converted to a common basis, through a factor estimated from the reactivity of the kinetic matching standard compound and Trolox, providing higher antioxidant data for espresso coffee (45.2–93 mM of Trolox). Red wine samples (23–33 mM) had higher antioxidant capacity than white wines (3.2–6.5 mM), while black tea (11.1–18.2 mM) showed lower results than green tea (20.4–25.5 mM). Moreover, considering the antioxidant value expressed on a weight basis as milligrams of vitamin C per serving of sample, green teas and red wines were those that presented higher antioxidant intake, 765 ± 51 and 688 ± 71 mg of ascorbic acid per serving, respectively.