Raw material changes and their processing parameters in an extrusion cooking process

In this work, the effects of raw material and process parameters on product expansion in a fish feed extrusion process were investigated. Four different recipes were studied with a pilot-scale twin-screw co-rotating extruder according to a set of pre-defined processing conditions. In the four recipes, wheat and protein contents were adjusted and compared with a reference sample. It has been found that a dimensionless equation can well correlate the process parameters and product bulk density for the four different recipe extrusion. The average deviation of the correlation for bulk density is 2.4%. The experimental data show that product expansion decreases with increase of protein content. Several different methods have been applied to quantitatively correlate the changes of raw material composition with product bulk density.