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

TLDR: In this article, the effects of hot air drying variables including: 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.

Abstract: 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.