Tackling postharvest tomato losses in tropical climates using a passive cooling blanket

• This article describes the design and deployment of a passive cooling system in sub-Saharan Africa. • The cooling system significantly lowered temperature and increased humidity. • Locally grown tomatoes stored inside the cooling blanket showed an increased shelf life by 2 days. • The system's low upfront cost and scalability allow it to be utilized by farmers in various settings, including on farms, in transit on motorcycles and at markets. • The effect of various irrigation regimes and harvest at various ripening stages on postharvest performance in the cooling blanket where successfully tested. In sub-Saharan Africa, >40 % of fruit and vegetables are lost between farm and consumer. Cooling produce after harvest is key to reducing these losses. Passive evaporative cooling offers a promising solution, particularly for smallholder farmers in low- and middle-income countries, but challenges related to cost, scalability and complexity limit its adoption. To address these challenges, we developed the charcoal cooling blanket (CCB), an affordable and scalable solution for storing fresh produce. In a pilot study in the Ugandan tomato supply chain, we tested the CCB against natural shade to improve tomato storage and transport. We also evaluated pre-harvest factors such as ripening stage and irrigation scheduling and post-harvest attributes such as weight, firmness, colour, soluble solids content (SSC) and acidity. CCB reduced the average ambient temperature by 1.5 °C, with a maximum reduction of up to 20 °C during the hottest periods. Relative humidity increased by 10 %, reducing tomato shrinkage. Storage in the CCB resulted in up to 10 % less weight loss, 20 % less firmness loss, slower colour change and a 4 % increase in the SSC/pH ratio compared to ambient conditions. Moderate water stress during cultivation combined with CCB storage reduced weight loss in green tomatoes by 17 %. Overall, CCB increased the quality index and shelf life of tomatoes by up to 60 %. The CCB has shown significant potential for reducing post-harvest losses, making it a viable option for preserving fresh produce and improving food security in low- and middle-income countries.