African Journal of Food Science and Technology

Abstract

Ascorbic acid is the only major nutrient derived from citrus fruits and dark green leafy vegetables consumed by a large proportion of the populace.This study was aimed at examining the overall effect of heat on ascorbic acid in selected fruits and vegetables. Citrus fruits and dark green leafy vegetables were sampled from the fruit and vegetable Market inMakurdi, Benue State,Nigeria. Ascorbic acid content of the dark green leafy vegetables and fruits were also determined while in the fresh state at ambient temperature of 37°C. The dark green leafy vegetables (pumpkin and bitter leaf) and juice from the fruits (orange and grape) were subjected to high temperatures of 50°C and 70°C by placing them in a water bath set at the respective temperatures. The study showed that the citrus fruits contained more ascorbic acid(61.18mg/100ml; 45.24mg/100ml) as compared to that of dark green leafy vegetables(41.75 mg/100ml; 38.71mg/100ml) in their fresh state at ambient temperature (37°C). In their fresh state, oranges had the highest amount of ascorbic acid while bitter leaf had the least ascorbic acid content. They all lost some amount of ascorbic acid when subjected to higher temperatures of 50°C and 70°C. However, the dark green vegetables lost more ascorbic acid than the citrus fruits when subjected to heat. Thus, it is advised that blanching should be the most appropriate means of cooking leafy vegetables and less heat applied to citrus fruits during processing especially while making fruit concentrates and juices. It is best to take citrus fruits raw in order to get maximum amount of the ascorbic acid content.