% of Cook of Pet food & Aquatic Feed by the MS3000 Medium Shear Extruder
Typical dry pet food or aquatic feed contain a wide range of ingredients. More often, they contain grains such as corn, wheat or rice. Those ingredients are rich in starch. Other sources of starch can come from potatoes or cassava.
Starch is not well digested in its raw state and needs to be cooked. Pets will suffer digestive problems when the starch is not well cooked. On the other hand, producing high quality fish pellet with the needed functionality requires high degree of starch gelatinization.
In an extruded diet, the starch play a major rule as a source of energy, binding agent and in the case of aquatic feed, it helps in producing the buoyancy needed in the floating fish feed. It also helps in keeping the integrity of the pellet intact in the water environment when the pellet is not immediately consumed by the fish or the shrimp.
When extruded, the conditions of temperature and moisture changes the starch structure as it irreversibly losses its crystallinity and swell to a gel. This is called gelatinization of the starch.
One of the criteria used when testing the efficiency of proper cooking of extruded product is the percent cook. Percent cook is the ratio of gelatinized starch as percent of total starch.
In the pet food industry, a ratio of over 80% is considered acceptable.
As we tested our Medium Shear Extruder, the samples of dog food processed were compared with a premium commercial dog food along with a sample of our High Shear extruded dog food. The degree of cook provided by the preconditioner alone was determined so that we can optimize the contribution of the preconditioner to partial cooking thus utilizing less specific mechanical energy.
Samples of different sizes of Medium Shear extruded floating catfish food were tested also. The following graphs show the excellent results that were achieved.