Modification of Parabolic Shaped Solar Dryer for Enhanced Performance in Preservation of Agricultural Produce. Nigerian Journal of Post-Harvest Research, 3(5), 90-99.

Postharvest losses of fruits and vegetables remain high in Nigeria due to continued reliance on traditional sun drying and limited access to electricity-powered dryers. This study presents the modification and performance evaluation of the parabolic-shaped solar dryer (PSSD) integrated with a secondary heat source and an improved airflow system, designed to address the limitations of conventional dryers in maintaining optimal drying conditions during nighttime and cloudy weather. The modified dryer was compared with an existing, non-modified unit under no-load and load conditions, using 190 kg of tomatoes as test material. Temperature, relative humidity, drying rate, colour change and moisture content were monitored during evaluation. Und both conditions, the modified dryer achieved higher internal temperatures and lower relative humidity compared to the non-modified dryer and ambient air, resulting in improved drying efficiency and overall performance. Drying curves exhibited an initial warming-up phase followed by a falling-rate period, with a peak drying rate of 36.6 kg/day observed in the modified dryer. A safe final moisture content of 12.3% was achieved in 96 hours, compared with 120 hours and 13.9% (dry basis) in the non-modified dryer. Colour analysis revealed a decrease in L* (Lightness), a* (Redness), and b* (yellowness) for both systems; however, overall colour difference (ΔE) was consistently lower in the modified dryer (≈18.9) than in the non-modified dryer (≈23.2), indicating superior colour retention. The modification enhanced thermal performance, drying efficiency, and quality preservation, demonstrating its potential to reduce postharvest losses in tomatoes and promote sustainable drying technologies for smallholder farmers.