Evaluation of effects of storage condition and processing on carotenoids, chlorophyll, and micronutrients in Gnetum africanum leaf

Abstract

Purpose: The aim of this study was to investigate the effects of ambient temperature storage condition (27-29°C) and domestic cooking on contents of carotenoids, chlorophylls, vitamins and minerals in the leaves of Gnetum africanum. Research method: Carotenoids were separated and analyzed by HPLC. Total-carotene content, vitamins and minerals were assessed spectrophotometrically. Main findings: Results indicated that G. africanumwas rich in lutein (528.87 µg g-1 (dry weight basis) and total β-carotene (248.10 µg g-1). There was no statistical increase in total β-carotene content due to cooking, but there was a decrease due to storage. Total β-carotene isomerized more during thermal processing than in storage. Cooking decreased (p>0.05) the contents of chlorophylls, water soluble vitamins and minerals. Cooking and storage of G. africanum resulted in significant losses in ascorbic acid, riboflavin and niacin. Cooking also reduced the potassium, calcium, magnesium and zinc. Iron contents of cooked and stored samples were higher than that of the raw sample. Research limitations: We had to travel over 600 km to use facilities for carotenoid analysis. Originality/value: The concentrations of lutein, β-carotene and certain micronutrients in G. africanumare much higher than typical contents in conventional edible leafy vegetables. The results of this study therefore provide evidence that G. africanum leaf could be an important contributor for improving the nutritional status of rural and urban people.