Extrude, dry and coat pet foods for artisanal appearance

Pet food producers can adjust aspects of the production process, including extrusion, drying and coating, to fine-tune the look of finished kibble and treats.

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(Andrea Gantz)
(Andrea Gantz)

Pet food producers can adjust aspects of the production process, including extrusion, drying and coating, to fine-tune the look of finished kibble and treats. By controlling these parameters, dog, cat and other pet food manufacturers may achieve customized, artisanal appearances, while availing of the economy of scale provided by industrial-scale equipment.

Artificially artisanal kibble and pet treat extrusion

Pet food and treat extrusion generally produces far higher volumes than can be sold by small dog, cat or other animal food companies. However, as more pet food start-ups enter the field, smaller companies may still use ingredients produced on extruders. Similarly, as consumers demand pet foods that resemble their own artisanal eats. However, the extrusion process tends to produce uniform kibble and treats that clearly were made using industrial methods. To address this, extruder operators can manipulate their machines to make mass-produced pet foods look like they came out of a small-batch oven. Two pet food industry experts shared tips for using an extruder to make artificially artisanal kibble and pet treats, during the Q&A of the Petfood Essentials CONNECT•ED presentation on preconditioning and extrusion by Will Henry, R&D for Extru-Tech.

“There are some tricks we can do at the extruder to kind of give it a non-cookie-cutter look,” Henry said.

When Henry’s team helps clients develop new products at the company’s pilot facility in Manhattan, Kansas, USA, they often do the opposite and turn an artisanal pet food or treat recipe into a process formulation. Part of that transformation involves keeping the sensory characteristics of the recipe produced in a mixing bowl.

Tricks to make extruded pet products look homemade

For example, to give texture to the outside of a product, extruder operators can mount a powder feeder. In a current project, Henry’s team will attach a powder feeder to the throat of the extruder. The powder feeder will drop whole steamrolled oats into the extruder.

“When it comes out the extruder, you're getting a nice biscuit shape, but it's got a texture with those steamrolled oats as well,” Henry said. "It gives you the mass production you need to hit a broader market at an economy of scale, but still gives you an artisanal kind of look and feel to the product."

Another trick Henry’s team uses is to turn the knives in the extruder around backwards. Instead of consistently cutting the product at a set shape, it becomes a bit more irregular. To create meat analogues, he uses a different technique.

“If you want it to look like just a chunk of meat that you pulled off of a cooked chicken breast, we've done those type of products with some adjustments at the die,” he said. “Sometimes we flip the geometry of the die around, so instead of funneling the product to a smaller shape, we funnel out to give it an irregular expansion characteristic.”

Extruded pet food ingredients for small companies

At a typical scale, pet food extruders produce 10 to 12 tons an hour, Henry said.

“The process of extrusion is really an extraordinarily high throughput starch cooking machine,” moderator Greg Aldrich, associate professor and pet food program coordinator at Kansas State University, said. “It's generally designed or engineered for large-scale production, so it may not fit in homemade or small-scale operation directly, and I'm going to emphasize that.”

For smaller companies that don’t need tons of kibble or treats per hour, extruders may come into play, Aldrich said.

He gave the example of using an extruder to produce sorghum crisps resembling puffed rice cereal. Those crisps then went into a formulation for something like a granola bar for dogs.

Drying and coating influence pet kibble, treat properties

After a pet food or treat is extruded, more variables come into play with the dryer. Three different types of machinery used to dry pet food and treats can influence those products. Griffiths G. Atungulu, Ph.D., associate professor of agriculture at the University of Arkansas, discussed how drying techniques affect kibble and other pet products during the during the Q&A that accompanied his Petfood Essentials CONNECT•ED presentation on coating, cooling and drying.

Different machinery dries pet products in different ways, Atungulu said. One common method blows hot air over the kibble in a conductive drying process.

“The way we dry with air, you have heated air coming in contact with your product,” he said. “Then the heat eventually moves from the surface of the product through the material. That kind of process is completely different from what we would get if you are using something like a microwave.”

Microwave and infrared radiation for drying pet food

Microwave drying of a pet product heats up the water molecules in the material in a volumetric way through a kind of radiative heating, Atungulu said.

“If you look at the structure of the food material that's dried using convective heated air [versus] a microwave dryer is going to be very different," he said. "The color can also change just because of the way the heat is moving through the material.”

Infrared dryers provide a third option for drying pet products. Infrared and microwave radiation both fall within the electromagnetic spectrum, Atungulu said, and therefore the techniques dry kibble and treats using similar physical principles.

However, because they have different wavelengths, the penetration of heat into the product is going to be very different, he said. Infrared has very shallow penetration and tends to heat the surface of the material, compared to microwave, which tend to heat deeper. Infrared, microwave and heated air dryers all differ from each other, which may provide varied tools for pet food manufacturers.

“I've seen cases where hybridizing those methods have brought completely different surface capabilities of the material,” Atungulu said.

Though not commonly used with extruded kibble pet food, dryers too can fine-tune the surface appearance of products, Aldrich said during Atungulu’s Q&A. However, some pet food makers have begun to explore the use of dryers to influence the final look of pet products.

"We can do all sorts of things in drying and coating that can alter the appearance of the product,” Aldrich said. “The dryer, if it is operated more like a baking oven, we can get color development through browning reaction. It takes a lighter tan product and it darkens it or browns it. It also develops some flavor.”

Along with affecting the color, drying and coating techniques add an artisanal baked appearance or allow kibble to emulate ingredients like carrots or meat.

Pet food producers use a variety of colored topical coatings, Aldrich said. In baked pet products, those surface coatings may be applied to a light brown biscuit, he said. By applying a red coating, the baked product takes on the appearance of meat.

“It's more about appealing to the consumer than it is the animal,” he said.

Likewise, pet food makers can apply visible pieces to the surface of the product, Aldrich said. For example, little bits of green or red give the visual appearance of peppers or carrots on the surface. Those pieces range in size from specks measuring 100 microns in diameter to actual whole pieces of other ingredients, including real carrots.

“There's a lot of options that we can play with to appeal to the consumers’ idea of what nutrition is,” he said.

Tweaking the extrusion, drying and coating of pet foods offers options for brands to mass produce a product resembling one crafted in a home kitchen.

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