Greenhouse solar drying and thin layer drying of fresh Kapenta(Stolothrissa Tanganicae)
Aduke, Ngira Rhoda
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The aim of this study was to carry out an experimental investigation on drying fresh Kapenta (Stolothrissa tanganicae), in a Greenhouse Solar Dryer and to evaluate a suitable thin-layer drying model for fresh Kapenta. The nutritional constituents and quality of dried Kapenta produced from a Greenhouse Solar Dryer and that dried in the open sun were also analysed. The Greenhouse Solar Dryer design; Kainji Solar Tent Dryer described by Olokor and Omojowo (2009) was adopted and constructed for this study. The length, width and height of the dryer were 1.5 metres by 1 metre by 1 metre, respectively. A rectangular wooden frame was fabricated and 20 mm diameter plastic pipes clamped on opposite ends to form the Greenhouse frame. Pieces of rock were spread within the base of the wooden frame and covered with black polythene. The Greenhouse plastic was fitted onto the entire Greenhouse framework. Kapenta was placed in a thin layer on a drying rack inside the Greenhouse Solar Dryer from 9.00 am and was dried until a constant weight of the samples was reached. Another set of two samples were placed on a drying rack in the open sun as control samples. The Kapenta in the Greenhouse Solar Dryer dried to a much lower moisture content compared to the Kapenta dried in the open sun. In order to develop a thin-layer drying model, fresh Kapenta was dried by convection in a hot air dryer at different air temperatures. The influence of the drying temperature (35, 45 and 55°C) on the moisture ratio and drying rate has been studied in this research. The experimental drying data obtained for Kapenta under varying temperatures was fitted commonly used thin-layer drying models by using non-linear least squares regression analysis. All the models were compared according to three statistical parameters, i.e. coefficient of correlation ( 2R ), the reduced chi-square ( 2 x ) and the root mean square error (RMSE). It was found that the coefficient of correlation values of Page were higher (0.9804-0.9970), and the corresponding reduced chi-square (0.0002-0.0012) and the root mean square error (0.0081-0.0328) values were lower as compared to the other models, indicating that the Page model is the best to describe drying curves of Kapenta among all the models. Based on Student’s t-test, the Kapenta dried in the Greenhouse Solar Dryer had higher nutritional values of protein fat and carbohydrates that differed significantly at 95% level of significance from the Kapenta dried in the open sun.
The University of Zambia
Solar Greenhouses-Design and Construction
olar Buildings-Design and Construction
- Engineering