Abstract

Traditional processing methods have an impact on nutritional quality of leafy vegetables. This impact may result in increased microbial count, risk of food poisoning and inability to prevent post-harvest losses thereby leading to malnutrition and subsequently food insecurities. Therefore, special processing methods to reduce the contamination while prolonging the shelf life of leafy vegetables are essential. The objective of this study was to determine the effect of time-based oven drying on the microbial profiling of cowpea [Vigna unguiculata (L.) Walp.] leaves. A study was conducted at Limpopo Agro-Food Technology Station laboratory with a constant oven drying temperature of 52°C. Two separate experiments were conducted for raw and cooked cowpea leaves with four treatments viz., 0 (sun-dried), 24, 48 and 72 h of oven-drying arranged in a randomized complete block design with five replications. Relative to control (sun-drying), oven-drying periods 24 h significantly increased Staphylococcus spp. in raw cowpea leaves by 6%, respectively. Relative to control (sun-drying) 72 h oven-drying period significantly decreased Shigella spp. by 92%. In cooked leaves, relative to control (sundrying), 72 h drying periods decreased both Shigella spp. and Staphylococcus spp. by 99 and 21%, respectively. Total coliform units of Salmonella spp., Escherichia coli, Pseudomonas spp. and Bacillus cereus were absent and/or at an undetectable level according to the Tempo Biomerieux system results. Cooking followed by oven-drying had negative effects on microorganism that were responsible for spoilage on cowpea leaves. Therefore, it is advisable to cook then dry leafy vegetables for longer (72 h of oven-drying) to reduce the total count of microorganism; however, this could be crucial to nutritional quality.