Effects of microwave heating on the antioxidant activities of tomato (Solanum lycopersicum)

Abstract

The aim of this study is to estimate phytochemical constituents and antioxidant activities of tomato slices treated by microwave heating. Two treatments time were applied, 30 and 300 s. Quantitative analyses of phenols, flavonoids, lycopene, followed by the evaluation of the antioxidant activity by DPPH (2,2-diphenyl-1-picrylhydrazyl) and ion chelating methods, were conducted on ethanolic extracts. Results showed the presence of these bioactive phytonutrients in fresh tomato and that their biodisponibility increases with the duration of the selected heat treatment. The phytochemical content showed important levels of polyphenols (1.92, 1.96, 6.95 mg gallic acid equivalent/g fresh matter) and flavonoids (2.33, 2.57, 10.68 mg RE/g fresh matter), in addition to lycopene (5.772, 31.8654, 40.71 mg/kg fresh matter) of non-treated, treated tomatoes at 30 s and treated tomatoes at 300 s, respectively. Results also revealed a high level of antioxidant activity by both methods with IC50 of 1.69, 1.50, 1.33 µg/ml, for DPPH method and IC50 of 401, 360.5, 299.91 µg/ml, for ion chelating ability. Thus, in our study, we demonstrated that microwave treatments enhance the nutritional quality of tomato slices by enhancing the biodisponibility of some of its content. Higher treatment time gives better results. Keywords: Tomato, Microwaves, Polyphenols, Lycopene, Ion chelating, DPPH radical scavenging