Effect of Hot Air Drying Variables on Phytochemicals and Antioxidant Capacity of Jew's Mallow (Corchorus olitorius L.) Leaves

Jew's mallow (Corchorus olitarius L.) is an important vegetable in Egypt. Fresh or dried Jew's mallow leaveshave a wide use and is great demand for domestic as well as export markets. The effects of hot air drying variablesincluding: air temperature (50, 60 and 70 oC), air velocity (0.2, 0.4 and 0.6 m/ s) and trays load (125 – 500 g/ 0.22 m2)on the antioxidant capacity and some phytochemicals content of Jew's mallow leaves were studied. The fresh Jew'smallow leaves exhibited high antioxidant activity (52.29% and 139.55 μmol trolox/ g dry weight, measured by DPPHand ABTS assays, respectively). The leaves had high contents of chlorophyll a and b (649.4 and 317.4 mg/ 100 g), totalphenolics (16.54 mg GAE/ g) and total flavonoids (117.88 mg quercetin equivalent/ g). Drying process resulted indrastic decreases in all studied properties except the β-carotene content. Antioxidant activity and phytochemicalscompounds contents decreased as air drying temperature and velocity decreased, relating to long drying times. Dryingat 60 oC and air velocity 0.6 m/ s had the lowest negative effect on the leaves antioxidant activity. Leaves dried at thehighest trays load (500 g/ 0.22 m2) also, showed the highest antioxidant activity and phytochemicals contents.

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