Physical quality of pelleted food. A feed model study.

In this study, a review and experimental work is presented on the relation between processing conditions and functional properties of feed constituents with respect to hardness and durability characteristics of pelleted feed. In the first three chapters, a literature overview is presented which describes the methodologies used to determine hardness and durability characteristics of pelleted feed. The second article deals with the effects of processing conditions on the physical quality of pelleted feed. In the last review, article an overview is presented on the effect of raw material constituents and pellet quality.The effects of processing conditions on changes in starch degree of gelatinization of tapioca meal and protein quality of soy grits (as two model feeds) have been studied. It was concluded that addition of steam and water had a larger effect on changes in the starch degree of gelatinization and the denaturation of protein than the amount of dissipated mechanical energy. Hardness and durability characteristics of pelleted feed were influenced by the amount of dissipated mechanical energy and the amount of steam used.Mixture studies were conducted in which the state of the model feed constituents -starch and protein- was altered and the subsequent effects on pellet hardness and durability were studied. From these studies it was concluded that an increase in the degree of gelatinization, or an increase in the amount of native protein leads to harder and more durable pellets. Possible explanations for these effects such as the change in deformability of the particles that make up the feed mash and the ability of the starch or protein to act as a binder, are described