Total antioxidant capacity, total phenolic content and iron and zinc dialyzability in selected Greek varieties of table olives, tomatoes and legumes from conventional and organic farming

Marina Drakou, Angeliki Birmpa, Antonios E. Koutelidakis, Michael Komaitis, Efstathios Z. Panagou, and Maria Kapsokefalou

Laboratory of Food Microbiology and Biotechnology of Foods, Department of Food Science and Human Nutrition, Agricultural University of Athens, Greece.

Abstract

The objective was to compare 10 types of table olives, 11 types of tomatoes and tomato products and 18 types of legumes from conventional or organic farming for selected nutritional properties. All products were tested for their total antioxidant capacity (TAC) (Ferric Reducing Antioxidant Power (FRAP) assay) and total phenolic content (Folin-Ciocalteau method). Tomatoes and legumes were further tested for iron and zinc dialyzability after in vitro digestion. Ascorbic acid content of tomatoes was also measured. The study resulted that the nutritional properties of olives, tomatoes and legumes tested were different among the various cultivars but, in most cases, not between products from organic or conventional farming. Natural black olives, cherry and santorini tomatoes and lentils exhibited superior nutritional properties.

Keywords: Bioavailability, iron, legumes, organic products, table olives, tomatoes, total antioxidant capacity, zinc.