ENHANCEMENT OF TOTAL PHENOLICS AND ANTIOXIDANT PROPERTIES OF SOME TROPICAL GREEN LEAFY VEGETABLES BY STEAM COOKING

This study sought to evaluate the effect of steam cooking on the vitamin C, total phenolics, total flavonoid and antioxidant properties (1,1-diphenyl-2-picrylhydrazyl [DPPH] free radical and 2,2-azinobis(3-ethylbenzo-thiazoline-6-sulfonate) [ABTS*] radical scavenging abilities, reducing property and Fe2+ chelating ability) of some tropical green leafy vegetables: Talinum triangulare, Ocimum gratissimum, Amaranthus hybridus, Telfairia occidentalis, Ipomea batata, Cnidoscolus aconitifolius, Baselia alba and Senecio biafrae leaves. The results of the study revealed that cooking causes a significant (P < 0.05) decrease in the vitamin C (raw [321.4842.0], cooked [198.2638.4 mg/100 g]) content. Conversely, there was a significant (P < 0.05) increase in the total phenol (raw [146.9693.8], cooked [272.91037.5 mg/100 g]), total flavonoid (raw [8.253.0], cooked [12.957.4 mg/100 g]), DPPH radical scavenging ability (raw [15.761.8], cooked [52.892.7%]), reducing property (raw: 28.361.8; cooked: 43.971.6 mg/100 g ascorbic acid equivalent [AAE]), Fe2+ chelating ability (raw [17.475.4], cooked [22.889.2%]) and ABTS* scavenging ability (raw [17.487.3], cooked [57.5113.2 mmol/100 g trolox equivalent antioxidant capacity]). In view of this, it could be concluded that steam cooking decreases the vitamin C content of all the vegetables, while it increased the phenolic content and antioxidant activities.