Effect of Processing on the Antioxidants (Vitamin C and Flavonoids) Constituents of Selected Leafy Vegetables

Abstract

The effect of different processing methods: fresh milling (FRM), sun drying (SND), oven drying (OVD), steaming (STM) and a combination of these methods on the vitamin C and flavonoids constituents of selected leafy vegetables Vernonia amygdalina, Gnetum africana, Gongronema latifolium and Ocimum gratissimum was evaluated. Results indicated that the leaves were rich sources of vitamin C and flavonoids. Fresh milling of samples was the most effective method of retaining vitamin C and flavonoids in all leaves followed by sun drying which accounted for 19.4-37.7% and 12.8-20.2% losses respectively. However a combination of steaming and oven drying (STM+OVD) had adverse effect on them and accounted for 27.8 65.0% and 18.6-27.7% losses respectively. Loss of vitamin C and flavonoids through different processing methods was significant at P<0.05 and the percentage (%) losses varied from one vegetable to the other.

Keywords: Leafy vegetables, vitamin C, flavonoids.