What is Extrusion and why Extruding?

What is Extrusion?Screws & Choke Plates

What is Extrusion and why Extruding?  A question I am sure many would ask.  Several definitions for extrusion exist – from the traditional “forcing material through a die or hole” to definitions focussing on other aspects of extrusion as well.

Extrusion, as it is applied in the animal feed industry, could not be discussed without focussing on extrusion as a Thermal Process.  By extruding feed ingredients and formulations, we involve heat energy as part of the extrusion process.

Therefore, a more descriptive definition in terms of animal feed manufacturing could be :

  1. Extrusion is a Thermal Process,
  2. where we knead and cook starchy and / or protein-based ingredients under specific moisture conditions,
  3. into a plastic-like dough of viscosity we can control during the process.
  4. We achieve primary “thermal cooking” through friction between feedstock (the formulation or ingredients we are extruding) and the internal extruder barrel components.
  5. We can also apply additional heat externally via
    • Barrel Jackets or Heater Bands, or
    • Direct injection of steam into the barrel at appropriate positions.
  6. Apart from creating a thermal effect as discussed above, we also apply shear forces to the dough creating very specific extrusion end results that could be controlled during operation.
  7. The mix of operating conditions as discussed above leads to gelatinisation of starch; denaturing of protein; minimising of anti-nutritional factors and neutralisation of microbial counts in feed ingredients and by-products used in animal feed manufacturing.

A more in-depth discussion of how temperature is generated is discussed in the Extrusion defined page of this website.

A complete Extruder is composed of various parts or zones in order to make it functional as the following diagram shows:What is Extrusion and Why Extruding?

  1. Mass Flow Surge Bin – making feedstock available for extrusion without flow-interruption.
  2. Volumetric Feeder – extracts feedstock from Surge Bin in “first-in-first-out” manner
  3. Preconditioner – conditions feedstock with steam and / or water or other liquids.  Some Thermal Processing starts taking place in the Preconditioner.
  4. Extruder – extrusion cooking of feedstock.  Primary point of Thermal Processing.
  5. Restriction Head – used for processing Oilseeds or in some cases wet products such as By-Products
  6. Cutter Head – used to produce shaped feeds such as Aquatic Feeds, Petfoods or other shaped animal feeds.

Why should we extrude?

Extrusion, just like any other feed milling process, has to be justified before money is invested into an extrusion line.  At least the following boxes should be ticked before we can justify an investment in extrusion:

  1. To minimise the effect of any “anti-nutritional” factors present in the Feed Ingredients we are using to make feeds with.  Soybeans is a classic example as it contains Anti-Nutritional Factors that prevents farmed animals to utilise the full nutritional value thereof.  Fortunately the majority of anti-nutritional factors are heat sensitive – extrusion is one of the most effective Thermal Processes available.
  2. To fulfil specific Process Requirements.  Do we need to shape final products for application as Petfood or Aquatic Feed?; do we have to sterilise a By-Product? do we have to control product density (as for floating aquatic feeds)?; etc.  Our page Effect of Extrusion outlines such potential process requirements.
  3. To maximise nutritional value of feed.  The main purpose of making animal feeds is to provide nutrition and to ensure safe feeds for farmed animal.  Extrusion processing maximises the digestibility of
    • Protein
    • Fat
    • Fiber

and therefore helps to produce edible meat, milk and eggs at the lowest cost per kilogram.

Remember : the ultimate goal is to maximise cash inflow into and minimise cash outflow from the business.  There is more than one way through which Extrusion can help achieving this goal.  The application opportunities for extrusion is only limited by our imagination and understanding of the opportunities around us.

Contact us today to discuss the extrusion solution that will fit your specific requirements or that will help to make use of locally available ingredients or by-products.