Food Extrusion testing machines have many applications within the food industry for texture assessment

Food extrusion can be divided into two categories; forward extrusion and back extrusion. Forward extrusion is when the test sample is placed into a confined container and then forced through an orifice or grid. The foods resistance to this extrusion is then measured. The size of the orifice or grid is usually changeable and the proper selection is contingent upon the product being measured and the textural property of interest. For example, sour cream, when not processed properly, can be grainy. By forcing sour cream through a small orifice, one will either see a smooth force level or a jagged one.

The jagged one happens when the grains alternately become plugged and unplugged in the orifice building then releasing back pressure. Back extrusion is a more common method of food extrusion testing. Back extrusion is typically performed with the product being measured is placed in an open top cylinder, and a piston with a diameter smaller than the cylinder, is forced down into the sample. The results is that the product flows between the space created by the piston and the cylinder and the resulting resistive force is measured. The key factor to consider in back extrusion is the gap between the piston and the cylinder. This is called the “annulus” and the smaller the annulus, the greater the resistance to the flow.