THE PHYSICAL-PROPERTIES OF EXTRUDED FOOD FOAMS

The extrusion cooking process has led to the production of many novel foamed foods. Their formation is critically dependent on the processing history and the local conditions at the die. The pore size generally decreases with a decrease in foam bulk density, while foamed plastics show the opposite trend. Narrow pore size distributions tend to be associated with foams where the pore size is small compared with the extrudate dimensions. A pendulum impact device has been used to assess the deformation of the different foams as a function of impact energy. The compressive strain increases to a maximum corresponding to the densification of these brittle foams. This contrasts with data for plastic foams.