Abstract

In rural areas of South Africa, different traditional processing methods such as cooking, sun-drying and appropriate storage are used predominantly to process leafy vegetables, however, these methods are casual due to levels of nutritional losses they cause as they increase prevalence of micronutrient deficiencies resulting in food insecurities. Therefore, these cause havoc in the rural populace. The objective of this study was to determine the effect of time-based oven-drying on essential mineral elements 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. Forty-eight and 72 h oven-drying periods significantly decreased raw cowpea leaf Fe, K, Mn, Na, Zn, P and S content. Relative to control, 48 h oven-drying period decreased K, Mn and Na by 6, 9 and 13%, respectively. Similarly, 72 h oven-drying period significantly decreased Fe, Zn, P and S content by 11, 16, 18 and 57%, respectively, in raw cowpea leaves. In cooked cowpea leaves, the decrease was observed in Zn and S mineral elements by 16 and 39%, respectively. In contrast, 72 h significantly increased cooked cowpea leaf Ca, Fe, K, Mg, Mn and Na content by 8, 8, 3 and 14%, respectively.