Effect of Extrusion Process Variables on Proximate Composition of Fish and Rice Flour Coextrudates

Abstract

Novel products made out of fish and rice flour are gaining importance due to high nutritional value. The proximate composition of these products largely depends on feed mix and also on the extrusion process variables. In the present research the effect of extrusion process variables like barrel temperature, x1 (100-200°C), screw speed, x2 (70-110 rpm), fish content of the feed, x3 (5-45 %) and feed moisture content, x4 (20-60%) was studied on the proximate composition like protein and fat content of the fish and rice flour coextrudates. Experiments were conducted based on rotatable experimental design for various combinations of process variables and the product proximate composition protein and fat content was evaluated. Second order polynomial regression equations developed has fitted the best based correlation coefficients of 0.99 and 0.94 and also based on observed and predicted plots. ANOVA table indicated that the linear terms of x1, x3 and x4 were found to be significant at P 95 rpm, x3 of about 45 % and x4 of about 20 % has resulted in maximization of fat content of the extrudates. The interaction of the process variables barrel temperature and feed moisture content played a major role on the protein and fat content of the extrudates. Further optimized process conditions obtained using GA has corroborated with the trends of RSM were x1=102.97, x2=107.67, x3=44.56 and x4=59.54 and x1=152.92, x2=109.95, x3=5.027 and x4=52.07 has predicted a maximum and minimum protein content of 46.65 and 12.41 %. The GA based process variables of x1=199.71, x2=70.01, x3=44.87 and x4=20.91 and x1=199.71, x2=109.10, x3=24.15 and x4=58.47 has predicted a maximum and minimum fat content of 3.52 and 0.057 %.