Effects of blanching time/temperature combination coupled with solar-drying on the nutritional and microbial quality of indigenous leafy vegetables in Kenya

Abstract

The abundance of indigenous leafy vegetables during the rainy seasons and the traditional preservation systems leads to post-harvest losses on nutrients. There is need to reduce these losses by seeking an alternative relatively cheaper, hygienic and locally adaptable preservation method. Solar drying could be a useful dehydration option. No sufficient data is available on a suitable combination of solar drying and blanching protocol for preservation of ILVs in Kenya. This study investigated the effects of controlled blanching time/temperature combination coupled with solar-drying on the nutritional and microbial load of three ILVs in finding a suitable preservation technique. The ILVs commonly consumed in Kenya, spiderplant (Cleome gynandra), slenderleaf (Crotalaria ochroleuca) and cowpeas (Vigna unguiculata) were used. Two blanching conditions (80oC/10 min and at 90oC/5 minutes) were tested. Blanching at 100oC for 30 min, followed by open sun-drying was used as control, while conventional oven drying of the ILVs was used as standard for comparison. Greatest nutrient loss was observed for ILVs that were blanched at 100oC for 30 min, then sundried. Most nutrients were retained at 80oC/10 min compared to those retained at 90oC/5 min. Microbial load (5.3-5.6 cfu/g) was significantly lower for solar dried ILVs (p<0.05) blanched at 90oC/5 min. This indicates that blanching at 80oC/10 min followed by solar drying is a potential option to be used as a local preservation technique for ILVs in Kenya.