An investigation of the influence of air-drying on the antioxidant components and antioxidant activity of New Zealand grown tomatoes : A dissertation submitted in partial fulfilment of the requirements for the Degree of Bachelor of Science with Honours at Lincoln University

Abstract

Three New Zealand grown tomato cultivars, Aranka, Encore, and Flavourine, were analysed for antioxidant activity in the hydrophilic (ABTS assay) and lipophilic (LipoFox assay) fractions, total phenolics, ascorbic acid, total lycopene (by two spectrophotometric methods), and colour. The same three cultivars were subjected to an air-drying treatment, and analysed for antioxidant activity, antioxidant components, and colour. In general, there was no significant difference (p<0. 01) between the fresh cultivars in terms of antioxidant activity or antioxidant components. The average values obtained for antioxidant components in the three fresh cultivars were: total phenolics, 613 mg GAE/100 g DM; ascorbic acid, 276 mg/100 g DM; total lycopene 25 mg/100 g DM and 38 mg/100 g DM by the hexane:acetone:ethanol extraction and tetrahydrofuran:methanol extraction, respectively. The total lycopene measured by the latter extraction method was significantly higher (p<0.01) than the former. Antioxidant activity of the fresh cultivars was 2917 μmole TEAC/100 g DM in the hydrophilic fraction, and IC₅₀ 284 mg sample/mL liposomes in the lipophilic fraction. Following air-drying treatment at 42°C for 48 hours, all cultivars showed decreases in total phenolics, ascorbic acid, and antioxidant activity, and increases in total lycopene. Colour analyses of the air-dried tomatoes showed that the colour degradation was minimal, and the colour was, in general, not significantly different (p<0.05) between each of the dried cultivars. Significant correlations (p<0.01) were seen between total phenolic and ascorbic acid contents of the tomatoes.