PET Food Processing - June 2020 - 45

EQUIPMENT

LOOKING
down the barrel

At the end of an extruder
barrel, form and function
are equally important.

By Chris Crawford | petfoodprocessing@sosland.com

F

For pet food and treat processors interested in options
for the end of the extruder barrel and how these affect
product and process applications, suppliers offer their
thoughts and products to best suit manufacturers' needs.

End-of-extruder experience

The extruder takes a stream of perishable and indigestible raw materials and "cooks" it into a highly digestible
and shelf-stable food source, said Will Henry, director
of research and development for Sabetha, Kan.-based
Extru-Tech Inc.
The process transforms the initial ingredients by mixing and shearing them into gelatinized starch and denatured proteins, and adds texture and flavor, explained
Dave Carney, area sales manager, pet food and aqua
feed, North America, Bühler, Cary, N.C.
"The exit drives expansion with flashing of steam,
and shapes are created with the die inserts," Carney said.
"The variable factors of temperature, specific mechanical
energy, liquid addition and screw elements all affect the
shape and consistency of the product."
The end of the extruder houses an assembly of concentric devices to form the product, Carney added.
"The parts include the end plate, distribution body,
diffuser plate and die plate," he explained. "The die
plate has die inserts to form the desired extruded shape.

Coextruded treats would not have the diffuser plate as
it can deliver up to 20 multiple streams depending on
machine size."
Extruders come in single-screw and twin-screw options.
"Pet food kibble is commonly made on single-screw
extruders," Carney said. "Twin-screw extruders provide
a better mix of ingredients and often make more complex shapes and designs."
Alan Kirkland, engineering manager, Ever Extruder,
Festus, Mo., said the cooking process with a single-screw
extruder is one of the most efficient and fastest processes,
and the final die plate cavity shape determines the kibble
shape, whether it be a round or a more detailed shape.
When discussing treats and end-of-barrel equipment, processors are generally limited to short-good
treats (less than an inch) that are cut immediately after
the die, said Daniel Tramp, technical sales, companion
animal division, Wenger Manufacturing Inc., Sabetha,
Kan. Items longer than that are typically allowed to cool
before cutting, he added.
A unique system that can be used for long-goods
treats is that of a twist die.
"This system allows for ropes of extruded product to
be twisted to create unique shapes and texture - similar
in shape to Twizzlers licorice," Tramp said.
Adrian Martinez-Kawas, Ph.D., international project

Components, such as
an EMV attachment,
can be added to the
end of an extruder
barrel to ensure food
safety upon start-up
and give operators
more control over
product flow.
Extru-Tech Inc.

www.petfoodprocessing.net | June 2020 | PET FOOD PROCESSING

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45

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PET Food Processing - June 2020

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