Solar Drying: A Means of Improving the Quality of Peanuts in Ghana

An indirect, passive, wooden dryer, with a galvanized steel panel (4.5 m2) and four wire mesh shelves (2.62 m2 each), was constructed in Kumasi, Ghana. The dryer was evaluated for its capacity in drying of freshly-harvested in-shell peanuts on a single layer (8.5 Kg), and then up-scaled to four layers (4x18 Kg). Equal amounts of peanuts, dried simultaneously on a concrete floor under the open sun, served as comparisons. The moisture content of solar dried peanuts decreased from 35.85-5.25% and 32.00 %-4.25% in the single-layer and four-layer drying, respectively, in 4 days. Faster drying rates were observed when peanuts had relatively higher moisture contents with R2 values ranging from 0.72-0.95. The average daily solar radiation ranged from 360-592.99 W/m2 and daily energies generated were from 42.24-69.16 MJ. The drying efficiency ranged from 1.50-6.47% in the single-layer drying and 23.07-24.93% in the four-layer drying whereas the thermal efficiency was 3.15-21.60% in the single-layer drying and 3.08-24.93% in the four-layer drying. Peanuts from the solar dryer had lower free fatty acid and peroxide values but higher germination percentage compared to open sundried peanuts. The study suggests that solar drying can be used effectively for improving peanut safety and preserving peanut quality in Ghana.