Design and fabrication of a direct passive solar dryer for tilapia fish filets

A direct passive solar dryer was designed and fabricated using plywood, aluminum foil and nails. A factorial experiment design having two factors at three levels and laid out in a completely randomized form was set up to dry tilapia fish fillets from a moisture content of 75% (wb) to a final moisture content of 15% (wb). Control experiment was also carried out. The moisture content changes, drying rate, bacterial and fungal loads were also noted. It was evident from the result, that the average drying time for fish fillets in the solar dryer is 33 h whereas the control experiment had an average value of 35 h. The collection and drying system efficiency were 53.88 and 47.51%, respectively. The bacterial count in CFU g^-1 (colony forming unit gram^-1 of product) ranged between 0.5×10³-1.2×10⁴ CFU g^-1 in the dried fish. On the other hand, in the control experiment the count was very high, with a maximum value of 2.5×10⁴ CFU g^-1. The fungal count in CFU g^-1 (colony forming unit gram^-1 of product) ranged between 0.3×10³-1.2×10⁴ CFU g^-1 in the dried fish. Whereas in the control experiment, the count is 3.0×10⁴ CFU g^-1. The drying rate was also found to decrease with time due to moisture depletion.