A Dutch company Almex is the specialist for single screw extruders and ContivarTM expanders, which are in use worldwide at fishfeed, petfood factories, animal feed mills, oil extracting and chemical factories.
Extrusion in feed production
Extrusion is a modern production procedure used during grain processing (cereals, pulses and other agricultural products) for feed mixtures and for petfoods. We differentiate between dry and wet extrusion. The procedures are quite similar, however, during wet extrusion, the material is steamed in a conditioner prior to processing.
Wet extrusion is a process during which high pressure, temperature and mechanical force is used to transform the wetted material, rich in starch, proteins and pulp, into a shapeable material. Gradually, proteins are denaturalized and starch components are gelatinized. When leaving the extruder, the material passes through expansion nozzles in die, where it loses water due to a pressure decrease. Multiple expansion results in the porous brittle structure of the product.
The main advantage of extrusion consists in protein denaturalization and starch component gelatinization, which improves the digestibility of the resulting material for animals. It also significantly reduces the content of anti-nutrition substances and eliminates contaminating micro-organisms. The low moisture content of the extruded material contributes to the product's longer durability.
The principle of expansion is similar to extrusion, but expanders differ from extruders on the outlet end. Expanders do not have a die and material is pressed through a gap between outlet head slide and the body of the expander. They are being installed in front of pellet mills for significant improvement of pelleting process, increase of digestibility and energetic value of the pellets while contemporary treatment against salmonella and other unwelcome bacteria.
Expanders are also used for final product production. Unlike pellets the expandate has particles of uneven size and is highly porous, but its production is cheaper than pelleting. The expandate is suitable for poultry, pigs and cattle.