A naturally ventilated solar-venturi dryer (NSD) was constructed using locally available materials to improve the quality of dry sweet potato slices (SPS) for small to medium scale farmers. The study investigated the efficiency of the NSD to reduce relative humidity (RH), solar radiation and temperature effect on firmness and color of dried SPS. The maximum temperature inside NSD was 44.4°C (12:00 pm) in an empty dryer and 34.1°C (13:00 pm) for a full filling NSD. The minimum RH in an empty dryer was 13.5 and 15.1% for a full filling NSD. The NSD was able to increase the temperature and reduce the RH at a minimum and maximum efficiency of 38.5 and 84.9% in a fulfilling NSD and 35.2 and 77.6% in an empty NSD. Thickness size and pre-treatment method had a significant (p<0.05) influence on color and firmness of dried SPS. The design of an NSD allows small to medium-scale farmers to process and preserve their produce at low cost, using the already available materials and structures.
Key words: Solar radiation; color; firmness, efficiency.
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