Effects of Pre-Treatments and Drying Temperatures on Drying Rate and Quality of African Catfish (Clarias gariepinus)

Abstract

Effects of pre-treatments and drying temperatures on the drying rate and the quality of African Catfish Clarias gariepinus was examined by drying samples of catfish under four different temperatures (40 ⁰C, 45 ⁰C, 50 ⁰C and 55 ⁰C) and four different pre-treatment methods (Salting, Sugaring, Blanching, and Control) using an experimental dryer. Drying of the fish samples for all the pre-treatments at 40 ⁰C to 55 ⁰C occurred in the falling rate period only showing that the predominant mechanism of mass transfer in drying process of catfish is that of internal mass transfer. The drying rate increases with increase in temperature for all the pre-treatment methods and decreases with time. The statistical analysis using a factorial design shows that drying rate was significant at (F; 0.05) but there is no significant difference in the pre-treatment methods as well as the interaction between drying temperature and the pre-treatment. The quality parameters (Protein, crude fat and Ash) measured decreases with increase in the drying temperature for all the samples with the blanched samples having the highest value of % protein of 55.94 at 45 ⁰C. The sugared samples have the least value of 43.82% at 55 ⁰C. The control has the highest amount of Ash 5.36% at 40 ⁰C and 4.04% for blanched samples at 55 ⁰C. Generally the values are higher for blanched samples and low for the sugar treated samples.

Keywords: Temperature, pre-treatment, falling rate, drying rate, quality.