EXTRUSION SHOWCASE
SINGLE SCREW EXTRUSION IN AQUAFEED
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by Joe Kearns, Owner, JK Kearns Consulting and Meridian Ingredients
he single screw extruder, the “World Heavy Weight Champion of Extrusion Tonnage Per Year Overall”, is the topic of concentration in this issue. Perhaps a review of the history and the developments the single screw extruder has undergone is in order and would be beneficial. The history of extrusion started years ago in an unusual fashion, by design and by accident. A major pet food group, Purina, took plastic extruders and changed them to make simple pet foods. Wenger, a small-localised equipment manufacturer in Kansas, was experimenting in making a high molasses feed for the livestock industry. Accidents happen, as in not turning on the liquid flows to the machine. The die, on an extrusion like machine, plugged except a few holes where the material came out highly expanded or “puffed up”. Studies were done on this product by Kansas State University confirming the product was cooked. No one cooked livestock feeds 60 to 70 years ago. What happened next changed or contributed greatly to the “World of Extrusion Cooking”. Purina marketed a product made for pets as noted above and their competition researched the method of its production. Kansas State, when asked, confirmed that they did not know how it was made but a small company (at that time) in Sabetha, Ks., Wenger, made something with similar characteristics. The phone rang in Sabetha and the research began in trying to figure out how to make this unusual occurrence happen again and on demand. The birth of a new commercial industry, extrusion cooking began. Initially the industry, which was basically just starting,
demanded simple pet foods and other products. Actually, one of the first extruders Wenger sold was for Venezuela and for floating fish feed. Some one noticed the feed floated and the vision of fish eating on the surface started in the 1950’s. It is hard to explain but not many know all of the situations that had to be overcome to make this system work. Examples include, raw materials and continuous operation. In my opinion, these were the major two areas of work initially. How did this system work and what made it work and why were ingredient qualities, grind and the percent in the formula important? What happened to the vitamins, fats oils and other components when extruded? How could the equipment be designed to run 24 hours a day with no issues? The research of both of these aspects, mostly by trial and error, changed over time into a science. If you can imagine, this was all in the experimental times and
everything had to be learned and researched. Were ingredients extrudable, what was the nutritional value after extrusion? How to move the product around, drying methods, coating, and everything surrounding the process had to be developed and proven. Extreme changes and advancements to date have occurred and as a result you have the modern-day extrusion process. Extrusion was not always so simple as there were many difficulties. Most difficulties were extended running time. One example is preconditioning, and it has advanced dramatically. Why? It did not work well having a simple preconditioner
28 | April 2018 - International Aquafeed