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The moisture diffusivity and activation energy of three tilapia fish varieties were determined under convective drying process (CDP). A locally fabricated drying system was used for the experiment at 60, 90/60 and 90 o C drying air temperatures. The drying rate showed falling rate period for all the drying processes with no sign of constant rate period. The moisture diffusivity values which increased with the increase in drying air temperature varied from 7.821 x 10-11 to 4.591 x 10-10 m 2 /s. The predicted Arrhenius constant and activation energy were 2.221 x 10-10 m 2 /s and 23.79 kJ/mol respectively.

BACKGROUND: Aflatoxin-contaminated grain consumption over the years has been known to result in serious health hazards for its consumers. The present study investigated the effects of harvest seasons and drying methods on aflatoxins in freshly harvested maize. A 2 × 3 × 3 × 3 × 3 factorial design was used; two harvesting seasons (dry and wet), maize varieties (P3966W, P4063W and P4226), moisture contents (0.15, 0.12, and 0.10 g kg −1 ), modern fabricated solar dryer (MFSD), hybrid biomass dryer (HBD) and open-air drying (OAD) methods, and packaging materials (plastic, jute and polyethylene bag) were studied, respectively. In total, 162 samples (n = 162) of maize grains (250 g each) were dried. The freshly harvested maize was shelled, dried, stored and analyzed for aflatoxins using high-performance liquid chromatography. The data obtained were subjected to statistical analysis.RESULTS: P3966W and P4063W with an initial moisture content of (0.226 and 0.234 g kg −1 ) reached a safe level of 0.10 g kg −1 using MFSD within 2-3 days, HBD within 2-3 days and OAD within 5 days. Variety P4226 with an initial moisture content of 0.228 g kg −1 reached a safe moisture level of 0.10 g kg −1 in 2, 3, and 7 days using MFSD, HBD and OAD, respectively. Aflatoxin concentration (56.00 ± 8.89 ∼g kg −1 ) was highest in P4063W at 0.15 g kg −1 moisture content, which exceeded the maximum permissible limits of 4 ∼g kg −1 recommended by the World Health Organization. CONCLUSION: Variety, type of dryer and season affect aflatoxin contamination of maize. The adoption of MFSD drastically reduced the duration of drying and consequently controlled contamination by aflatoxins.

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