Extrusion cooking was applied to the processing of pet foods from animal by-products having high moisture content (i. e., swine liver and guts) as main raw materials. To obtain the extruded product of good shape-holding property, various combinations of the material and the running conditions of twin screw extruder were examined.
Good textured products were obtained when the 4: 1 Mixture of liver and wheat flour or the 3: 2 mixture of guts and wheat flour was processed. Increase in the content of the animal by-products resulted in decline of shape-holding property of the extruded products. Optimal speed of screw revolution was found to be 150-170 rpm.
Good shape-holding property was achieved when 71% of the mixture of liver an d guts was combined with 11% of corn flour,9% of dehulled soybean meal and 9% of wheat flour (see Table 4, running No.12). Although the addition of 12% of feather meal into the material caused the inferior shape-holding property, the property was satisfactorily improved when the material containing feather meal was processed at high barrel temperature such as 103°C (Table 4, running No.14). It was found that the gelatinization of starch and/or the gelation of dehulled soybean meal were necessary to obtain good textured products in which the broken pieces of liver and guts were distributed in the stable structure.

View full abstract

for the purpose of making efficient use of animal by-products(stomach, intestines and liver), a pet food was produced using twin screw extruder, and the storage test, the nutrient analysis and the palatability test of the extruded products were carried out.
Bacterial counts of animal by-products used as materials were markedly reduced by the extrusion cooking. Coliform was not detected at all from extruded products. Increase of acidly due to oxidation of fat was not observed during the storage of the extruded products. There was little or no difference of the quality between storages at 25°C and 4°C for 26 days.
As the results of nutrient analysis, it was confirmed that the contents of protein, fat and carbohydrate of the products were within the desirable range of nutrient requirements for dog.
In palatability test using 10 beagle dogs, feed intake decreased as the time proceeded, but it increased by moistening the pet foods with suitable amount of water.

View full abstract