When it comes to extruding complete diets such as pet food, fish feed or something like pig starters that have multiple ingredients, close attention should be given to how ingredients react to the extrusion process. Certain ingredients can be adversely affected by heat and pressure generated during extrusion. In this blog, I’m going to go over a few examples to give you an idea of what can happen to ingredients and ways to remedy or minimize the effects.
The most important ingredients that can be affected by extrusion are vitamins. Vitamins can be somewhat fragile with short shelf life even without being subjected to extrusion. One example is Vitamin C, which is especially sensitive to heat. The loss experienced during extrusion can be overcome by formulating 25% over the normal dosage. Another option is to use what is known as protected vitamin C. There are several on the market that work well with extrusion. Protected vitamin C was originally designed for use in pellet mills because it has a protective coating that lessens the adverse effects of heat and pressure. Another way to prevent affecting the quality of your vitamins, in some cases, can be by adding them in post-extrusion with a mixer or sprayed on. In other cases, like shaped products, they need to be suspended in the pre-extruded mix. It’s usually best to consult with the company that manufactures your vitamins with concerns associated with your process because they can provide information about vitamin stability as it relates to your needs.
Another example of ingredients that do not tolerate extrusion heat and pressure are probiotics. As probiotics are live bacteria, they do not survive the extrusion process. Post application is the only way to include probiotics in your finished product without negatively affecting its quality. Often the probiotic is suspended in a liquid or possibly a vegetable oil and sprayed on – similar to post application of fat to pet foods.
When it comes to including a variety of ingredients into your formulation, you must not only take into consideration their sensitivity to heat and pressure but also how that can affect the quality of your end product.