Dry & semi-moist pet food

Most dry and semi-moist pet foods are made either on an expander or an extruder. First, the raw materials are blended either manually or automatically by computer in accordance with recipes developed by animal nutritionists. This mixture is fed into an expander, and steam or hot water is added. The mixture is then subjected to steam, pressure, and high heat while being extruded through dies that determine the shape of the final product and puffed like popcorn. The food is allowed to dry and afterwards often sprayed with fat, digests or other compounds to make it more palatable. This cooking process kills bacteria, but the sterility of the final product may be affected during the subsequent drying, fat coating, and packaging process.

Other pet foods are baked at high temperatures rather than extruded. This gives a dense, crunchy kibble that is palatable without the addition of sprayed on palatability enhancers. Measured by volume, not by weight, animals can be fed about 25% less of a baked food than of an extruded food.