Effect of Boiling and Wet Frying on Nutritional and Antinutrients Content of Traditional Vegetables Commonly Consumed in Malawi

Abstract

This study was carried out to evaluate the effects of boiling and wet frying on nutritional and antinutrients content of Amaranth hybridus, Moringa oleifera, Bidens pilosa (black jack), Corchorus olitorius (Jute mallow) and Ipomea batatas (sweet potato) leaves. The edible portions of the vegetables were either boiled or wet fried for ten minutes then dried alongside the raw vegetables under the shade. Crude fats, minerals, vitamins and antinutrients were determined in the dried materials. Wet frying increased the oil content of the vegetables by a range of 15.49% to 28.40 % and was hence associated with lower % ash and mineral contents. Wet frying significantly reduced (P≤0.05) beta-carotene in all the vegetables except in jute mallow. Boiling had no significant effect on beta-carotene in most of the vegetables. Boiling significantly reduced (P≤0.05) ascorbic acid in all the vegetables while wet frying preserved ascorbic acid in all the vegetables. Both boiling and wet frying significantly reduced (P≤0.05) oxalates in all the vegetables except in black jack. Both boiling and wet frying significantly (P≤0.05) reduced the concentration of phytates in most of the vegetables. However, boiling was more effective in reducing the amount of phytates. Boiling reduced higher concentrations of tannins in all the vegetables as compared to wet frying. Boiling was associated with better retention of minerals and beta-carotene, and greater reduction of antinutrients in most of the vegetables. Wet frying was more advantageous in retaining vitamin C. The different species showed differences in retention of various minerals and vitamins.