Amylase utilization for the extrusion of dog diets

Abstract

Effects of amylase addition on extruder parameters, cost of extrusion, kibble quality and digestibility of dog food were measured in two separate experiments. In experiment 1, 120 kilo-novo-α-amilase-unit (KNU)/kg of heat stable α-amylase produced by Bacillus licheniformis was added in liquid form during a preconditioning period. In experiment 2 3684KNU/kg of heat stable α-amylase produced by Aspergillus oryzae was mixed with the ingredients before extrusion. The diets were processed in a single screw extruder and submitted to digestibility and on experiment 1 also to palatability tests. Digestibility was tested using 12 dogs, six per diet. Data were submitted to analysis of variance followed by F-test. Amylase addition altered extrusion parameters in both experiments (P<0.05), with higher output (kg of dry matter [DM]/h; 28% and 43% higher in experiments 1 and 2) and less electric energy consumption (kW to produce 100kg DM; 22% and 29% lower in experiments 1 and 2). Kibble appearance and quality [density (g/L), cutting force (g), and starch gelatinization degree (%)] did not change with enzyme treatment (P>0.05). Likewise, enzyme addition did not change nutrient digestibility, fecal dry matter or food palatability (P<0.05). Taken together our results suggest that amylase promoted the breakdown of amylose chains, thereby reducing the dough viscosity and resistance inside the extruder which allowed for higher product flow and less electricity energy consumption without altering food quality.