IMPROVED FISH DRYING USING A POLYTHENE SOLAR DRYER

摘要

Post-harvest fish losses along Lake Turkana beaches were estimated to be about 60%. One of the main causes of loss was the low technology used in sun drying, resulting in high contamination of fish with sand. Further, the drying process is slow, resulting in a product that is of low quality with a short shelf life, consequently loss of income to fishers. It was therefore essential to identify, test and adapt appropriate technology to shorten drying time, improve product quality and increase shelf life of fishery products. This study assessed the effectiveness and efficiency of drying fish using solar dryer made of polythene (PE) sheets compared to the traditional open drying. Five drying systems consisting of a bamboo solar dryer on the ground, a raised solar dryer, a plywood solar dryer with black and another with white polythene sheet, were tested. Fish was harvested, split, washed and dried using the different systems. The temperature inside the drying chamber increased from 33 °C to 56 °C, representing an increase by factor of 69.6%. The temperature inside the fish increased from ambient temperature to a maximum of 62.9 °C, indicating an increase factor of 90.6%. Comparatively, the maximum temperature attained under open drying was 42.5 °C, which indicates an increase factor of 28.8%. The enhanced temperature during solar drying reduced drying time from 48 hours to 30 hours. The drying ratio in solar dryer was about 0.28-0.30 compared to 0.29 under open drying. The water activity attainedwithin 30 hours under solar dryer was 0.39-0.41 compared to 0.39-0.55 under open drying. The results demonstrate that solar drying is more effective and efficient than open drying. In addition, solar dried fish products are of higher quality, with significantly less sand, have a firm texture, fresh fish odour and an extended shelf life of over six months. Solar dryers also have lower operating costs than mechanized dryers. In conclusion, solar dryers shorten drying time, improve product quality, extendthe shelf life of the products, reduce costs and thus improve income to fishers.