Evaporative cold storage for African indigenous vegetables

High postharvest losses of African indigenous vegetables (AIVs) like amaranth and African nightshade limit both their availability for consumption and processing. Evaporative cold storage is proposed to address these losses in rural areas. A mixed-method approach was used. This included a qualitative strengths, weaknesses, opportunities, threats, and analytical hierarchy process (SWOT-AHP) evaluation, as well as experimental studies on the impact of evaporative charcoal coolers and brick coolers on vegetable quality. Overall, AIV value chain stakeholders perceived evaporative cold storage as highly necessary, given the expected benefit of reducing postharvest losses as AIV production increases. Its perceived main strengths were: maintaining vegetable quality, extending shelf-life, and the possibility to operate without electricity. However, knowledge of its establishment and operation, dependence on environmental conditions, high labour input, and potential user conflicts are key weaknesses and threats to be addressed. Compared to ambient conditions, temperature reduction (2.0 °C–8.5 °C and 2.4 °C–11.2 °C), and relative humidity increase (15.5 %–47.1 % and 10.3 %–49.3 %) were attained in the evaporative charcoal cooler and brick coolers, respectively. Fresh weight loss was reduced by 75.2 % and 64.0 % for amaranth, and by 72.8 % and 64.7 % for African nightshade in the charcoal and brick coolers, respectively, enabling shelf-life extension from 3 to 6 days. Nutritionally, proteins, minerals (Ca, P, K, Mg, Fe, Zn), and bioactive compounds such as total phenolic acids and flavonoids were maintained during evaporative cold storage. In conclusion, first, the SWOT-AHP analysis can guide the design and support the adoption of evaporative cold storage technologies, and second, evaporative coolers are viable options for maintaining quality and reducing postharvest losses of perishable crops such as African nightshade and amaranth in rural regions.