Characterization of Functional Physical Properties of The Dry Pet Food Manufactured with Animal, Plant, and Microalgae Ingredients

Abstract

The aim of the thesis is to gain better understanding on the effects of defatted microalgae biomass (Desmodesmus sp.), vital wheat gluten and potato protein on physical qualities of extruded dry pet food. Two experiments were conducted to investigate the effects. In the first experiment, microalgae (DMG) replaced poultry meal partially, at inclusion rate of 10%, 15% and 20%. Higher inclusion rates of DMG resulted in lower moisture content, lower water activity, but higher hardness and durability. Increasing extrusion water rate and decreasing screw speed improves expansion of pellets made with 15% and 20% DMG. Only extruded pellets produced with 20% DMG achieved acceptable water activity (< 0.6). In the second experiment, poultry meal is replaced with vital wheat gluten and potato protein at ratio 1:1. The experiment showed that the plant proteins improved expansion ratio, hardness, and durability but extruded pellets have high moisture content and unacceptably high-water activity (both were > 0.6). The results obtained from the thesis shows that microalgae biomass, vital wheat gluten and potato protein may be used in place of animal protein to improve physical qualities of extruded feeds, especially pet food. Keywords: extrusion, Desmodesmus sp., microalgae, vital wheat gluten, potato protein, physical quality, expansion ratio, moisture content, water activity, hardness, pellet durability index, pet food.