Pellet Mill vs. Extrusion
More often than none, during exhibits and shows we encounter visitors confusing an extruder with a pellet mill. The International Poultry Production Exposition (IPPE) that was held January 27-29, 2015 was no exception.
As some prospects examined our medium shear extruder (upper right hand corner), they were curious about the capacity of our “pellet mill”.
We always take the question as an opportunity to educate those who are not familiar with the extrusion technology, as it is easy to get confused.
The similarity of a pellet mill and the extruder can be summarized as follows:
1-Both utilize steam, pressure and temperature.
2-Both have dies to form the pellets however, they work on different principles:
The differences are the following:
1- A pellet mill shapes the pellets by compression through long land dies thus the pellet is dense. In most cases, a pellet binder is need in the formula to facilitate the cohesion of the pellet.
2- An extruder will expand the pellet through substantial gelatinization of the starch, expansion and increased porosity thus the reduction of the density. No need for the addition of a pellet binder in most cases.
3- In the case of floating fish feed, extrusion allows you to control the buoyancy of the pellet by the degree of starch gelatinization dictated by many factors such as the moisture content, extrusion temperature, and amount of shear generated and the size of the die used.
4- In pet food, palatability and lower microbial load are crucial and extrusion enhances both.
5- Extrusion allows you to use higher level of oil or fat without creating much fines thus higher integrity of the pellet.
The bottom line, while a pellet mill is mainly utilized to shape or produce a pellet, an extruder has many functions and shaping is only one of them. Visit our website to learn more about Insta-Pro International Extruders.
