Catfish Lab Report

2. Materials and Methods

2.1 Materials

Freshly harvested live-catfish (Clarias gariepinus) of about 6 months old, averagely weighing 524±20 g with an average length of 42±2 cm each were obtained from the Fisheries Research and Teaching Farm of the Federal University of Technology, Akure (FUTA), Ondo State, Nigeria. Common salt (NaCl–Mr. ChefTM) used for brine was purchased from a local market in Akure. The convective dryer (Model 2012, Korea) was obtained from Dickem Aquatech Nigeria Limited., Isashi, Lagos and installed for use in the food processing laboratory of the Department of Food Science and Technology, FUTA. Other chemicals used for analyses were of analytical grade.

2.2 Methods

2.2.1. Experimental design for catfish processing

A

Eight of which were equidistantly fixed around the wall of the cylindrical drying chamber with connections to a temperature regulator. The dryer was a double walled insulated stainless steel of 2 cm thickness and contained a set of three mesh trays in the drying chamber on which the brined catfish were arranged. The dryer was preheated to the desired temperature while the samples were being prepared to ensure temperature stability when the fish will be introduced. A dry bulb thermometer was hung inside the dryer through the vent at the top to monitor the temperature. The fish were occasionally checked to ensure no case hardening occurred during drying. The drying of catfish at 90, 110 and 130oC was done for 27hr, 24hr:40 min and 12hr:49 min, respectively. Samples with similar temperature factor were dried as a batch. Dehydrated catfish were cooled and muscle parts milled with the aid of a blender (MARLEX Electroline, Dabhel, Daman (UT)), sealed in polyethylene and labelled prior analyses. The production of dehydrated catfish is represented in Fig. 1.

2.2.4. Determination of proximate composition

Analysis of the proximate composition of the dehydrated catfish was done by the method of Association of Official Analytical Chemists (AOAC, 2005) to determine the percentages of moisture, crude protein, crude fat and ash contents.

2.2.5. Determination of rancidity

Significance was accepted at p<0.05. The data was fitted into RSM models. To correlate the response with the independent variables, multiple regressions were used to fit the coefficient of the polynomial model which was further subjected to backward regression/ transformation analysis to improve the fit. The lack-of-fit, coefficient of determination (R2), adjusted R2, predicted R2 and adequate precision were used to evaluate the quality of the fitted model. The response surface plots were prepared to represent a function of two independent variables while fixing the other variable at the optimal value. Predicted numerical multi response optimisation was done using the desirability concept. The fitted quadratic response model is as described in Eq. 1 (Awolu and Layokun,