Antioxidant assays – consistent findings from FRAP and ORAC reveal a negative impact of organic cultivation on antioxidant potential in spinach but not watercress or rocket leaves
Article first published online: 16 OCT 2013
© 2013 The Authors. Food Science & Nutrition published by Wiley Periodicals, Inc.
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Food Science & Nutrition
Volume 1, Issue 6, pages 439–444, November 2013
How to Cite
Food Science & Nutrition 2013; 1(6): 439–444
- Issue published online: 12 NOV 2013
- Article first published online: 16 OCT 2013
- Manuscript Accepted: 27 AUG 2013
- Manuscript Revised: 21 AUG 2013
- Manuscript Received: 4 JUN 2013
- The University of Southampton
- Vitacress Salads Ltd
- leafy salad crops;
- organic agriculture;
Watercress (Rorippa nasturtium-aquaticum), wild rocket (Diplotaxis tenuifolia), and spinach (Spinacia oleracea) are commercial crops reported to have high concentrations of antioxidants, possibly contributing to disease prevention following human consumption. Following analysis of supermarket-purchased salad leaves, we report the antioxidant content potential of these species using two comparable techniques assessing the consistency between the assays – by the ferric reducing antioxidant power (FRAP) assay and the oxygen radical absorbance capacity (ORAC) assay. The leaves were harvested from both conventionally and organically managed crops, to investigate whether organic agriculture results in improved crop quality. Watercress had the highest FRAP and ability to scavenge free radicals, followed by spinach and rocket. For watercress and rocket, there was no significant effect of organic agriculture on FRAP and ORAC, but for spinach, the antioxidant potential was reduced and this was significant at the 5% level of probability for FRAP but not ORAC, although the trend was clear in both tests. We conclude that there is variation in salad crop antioxidant potential and that FRAP and ORAC are useful techniques for measuring antioxidants in these salad crops with similar ranking for each salad crop studied.