Effects of corn sample, mill type, and particle size on corn curl and pet food extrudates

The effects of corn sample, grinder type, and particle size of ground corn on the extrusion of corn curls and pet food were studied. Extrusion runs we re conducted using a twin-screw extruder. Properties of corn curl and pet f ood extrudates were affected significantly by corn samples obtained from di fferent parts of the country (Nebraska, Illinois, and Texas), even though g rinding and extrusion parameters were held constant. The type of grinder us ed to grind the corn had an effect on extrusion properties. The volumetric expansion index (VEI) of extrudate from pin-milled samples was lower than t hat of extrudate from the same corn ground in a hammer mill or roller mill. Small particle size, obtained by grinding corn in a hammer mill with diffe rent screen sizes, produced extrudate with a significantly higher VEI than extrudate from coarse or medium-sized particles.