Effect of Soaking Time and Volume of Water on the Ascorbic Acid Content of Three Nigerian Green Leafy Vegetables

Abstract

Freshly harvested leaves (Heinsia crinata, Talinum triangulare, and Venonia amygdalina) were subjected to different pre-processing treatments; slicing, slicing with salt and squeeze-washing; a portion of whole leaves was used as control. Each sample was soaked twice; in 1 litre and 2 litres of distilled water for 480 min. The 2, 6-dichlorophenol-indophenol Titrimetric method was used to determine the ascorbic acid (AA) content of the fresh leaves. During soaking, the trend of loss was monitored for each treatment every 120 min. The AA content of fresh H. crinata was 73.42 mg/100 g of which 49.7–71.9% was lost; fresh T. triangulare had 337.30 mg/100 g of which 54.9–93.2% was lost and fresh V. amydalina had 121.00 mg/100 g of which 49.9–89.1% was lost during soaking. The pre-processing treatments increased the degree of AA loss in the three leafy vegetables and the higher the soaking time, the higher the AA loss.

Keywords: Ascorbic acid, soaking, Heinsia crinata, Talinum triangulare, Vernonia amygdalina