Evaluation of Effects of Storage Condition and Processing on Carotenoids, Chlorophyll, Vitamins and Minerals in a Water Leaf (Talinum triangulare)

Abstract

To alleviate hidden hunger on a long term basis, there is need to establish the nutrient composition of vegetables and determine the level of their incorporation into diets to meet body requirements of relevant vitamins and minerals. This research was aimed at evaluating the nutrient composition and changes in nutrients induced by processing and storage of an underutilized leafy vegetable (Talinum triangulare) with good potentials for alleviating micronutrient malnutrition. Changes in carotenoids, chlorophylls, selected vitamins (ascorbic acid, riboflavin, thiamin, vitamin K and niacin) and minerals (potassium, calcium, magnesium, zinc and iron) of T. triangulare leaf during moist heat treatment and storage (28±2°C) were evaluated. HPLC was used to determine the carotenoid profile. Results indicated that the raw leaf contained moderate amounts of lutein (124.03 µg/gdwt) and total β-carotene (45.42µg/gdwt). Cooking and storage significantly (p > 0.05) increased the contents of Total- β-carotene. Cooked leaf samples contained more trans/cis-isomers of β-carotene than raw and stored samples. Initial concentration of chlorophyll a, chlorophyll b and chlorophyll a/b ratio were 2.62, 0.94 mg/100 gfwt and 2.78 respectively. T triangulare was found to be a good source of magnesium, ascorbic acid and zinc. Cooking decreased the contents of chlorophylls, water-soluble vitamins and minerals significantly (p>0.05), but remarkably increased the pro-vitamin A content of T. triangulare. Storage resulted in the reduction of vitamins and minerals. The levels of β-carotene (pro-Vitamin A) in cooked water leaf, riboflavin, ascorbic acid and phylloquinone are adequate to meet their corresponding in Recommended Daily Allowances (RDA) s for children and adults.