One of the biggest advantages of extrusion is that it allows the product to cook while forming, by heat that’s either generated through friction or introduced externally. Not only is this faster and more energy-efficient; it cooks the food more thoroughly and safely, improves digestibility due to factors like increased gelatinization of starches, and allows more options for appealing product shapes.
“As a continuous processing tool, the extruder performs feeding, mixing, cooking, flavoring and shaping, in an enclosed, precisely controlled environment that ensures product consistency and process reliability,” says Gilles Maller, vice president of sales at Clextral Inc. (www.clextral.com).
The choice between mechanical and external heat, almost always steam, as an energy source in an extruder is sometimes driven by cost factors instead of processing considerations. Galen Rokey, director of process technology for the companion animal division of Wenger Manufacturing (www.wenger.com), says that, in most cases, externally supplied heat costs about half as much as mechanical energy. Some Wenger extruders come with “thermal twin technology,” which enables users to introduce steam heating per their preference.
More generally, extrusion allows flexibility in processing, Maller says. “One extruder can process multiple products by varying the production parameters (recipe, cooking temperature, screw configuration, residence time, etc.) and offers great flexibility to process a range of raw materials. This advantage is very important today with the trend of humanization of pet foods that has resulted in many new ingredient formulations.”
This kind of flexibility enables extruded pet food to be made to fit specific pet profiles, such as age, gender, energy requirements and nutritional restrictions, by allowing automated startup and shut down for product changes and simplified changeovers, he says.
Clextral’s innovations to extruders often used for pet food include Preconditioner+ with Advanced Filling Control, which improves the process of precooking the product before it enters the extruder barrel. Among other benefits, this allows pet food processors to add high levels of meat emulsion to the other ingredients prior to extrusion.
Another Clextral innovation is Evolum+ with Advanced Thermal Control, a self-learning technology that monitors process conditions and adjusts to changes to maintain process and product consistency. Maller says this allows for up to 70 percent more process stability and up to 20 percent energy savings.
As pet food becomes more versatile and, yes, more “human,” processing techniques will have to evolve and become more sophisticated to keep pace.
“We all see humanization of pet foods still being a predominant factor in the coming years and the challenges that go with that,” Lindley says. “With demand and supply on proteins and protein quality changing pet food recipes on a regular basis, processing technology is placed at the fore to handle such a wide range of specifications.”