Study On Extrusion Processing And Mechanism Of Pet Food

The dog food formula and extrusion process were established in the paper and the extrusion technological parameters were optimized through quadratic regression model in which the expansion index and starch gelatinization degree(SGD)were used as the core quality indexes of dog food by Respond Surface Method.The P value was less than 0.001 and R2 were 0.9543 and 0.9588,respectively,which indicated that the model could accurately predict the effects of extrusion parameters on the dog food expansion index and SGD.The optimal technological conditions were:material moisture content 22%,screw speed 35Hz(1Hz=5rpm),feed speed 30Hz(1Hz=2rpm),barrel temperature 150?.In this condition,the expansion index was 1.36,SGD was 89.42%.The water solubility index(WSI),water absorption index(WAI),starch and protein digestibility and texture characteristics were analysed.The results showed that four parameters had significant effects on the physicochemical and textural properties of raw materials.After extrusion,protein digestibility increased 8.8%and SGD increased 62.49%,indicating that extrusion could effectively enhance the protein digestibility.The effects of different storage temperatures and potassium sorbate additive amounts on the growing of molds were investigated.In 23-37?,increasing the barrel temperature and the amount of added potassium sorbate could significantly inhibit the growing of molds.The Gompertz growth model was used to predict the growth of molds at the three different storage temperatures with potassium sorbate content of 0.10%,and four potassium sorbate contents at storage temperature of 23?.The correlation coefficients R2 were 0.9803 and 0.9905,respectively.Therefore,this model had a good fitting.