Effect of extrusion process parameters on pellet crumbliness in fish feed production

The article presents the results of studying the pellets crumbliness index of a pilot batch of extruded compound feed for pike-perch. The regimes of extruded pellets fish compound feed production with minimal crumbling were defined using a mathematical model. A 3-factorial central composite design was implemented to obtain a mathematical model of the process of extrudate resulting in the second-degree polynomial. The process influencing factors include the feed mixture moisture W (%), extrusion temperature T (°C) and steam pressure P (MPa). Experimental studies were conducted according to the experimental plan. The experimental data obtained were entered into the planning matrix. Experimental data was processed in a program prepared in Microsoft Excel.  As a result, an adequate second-order mathematical model describing the dependence of the crumbliness index on the feed mixture moisture before extrusion, extrusion temperature and steam pressure was obtained. The mathematical model adequacy was tested based on Fisher's variance ratio. The Fisher criterion is an important statistical tool for verifying the adequacy of the model and analyzing the variance. The analysis of the obtained model and its graphical interpretation are presented. A good extrusion process mathematical model was developed. The fundamental principles of feed mixture processing on a single-screw extruder and the choice of its rational parameters ensure the production of extruded compound feed pellets for pike-perch with minimal crumbling were studied. A minimal crumbling is provided at the following values of the factors - feed mixture moisture before extrusion is 32%, extrusion temperature is 132 °C, and pressure is 0.4 MPa. In the selected levels of factors, the calculated value of extruded pellets crumbling was 1.02%.