PET Food Processing - March 2018 - 64


"Instead of buying a larger capacity
and only running it half the time, buy
a line for five tons and run five tons."
Mian Riaz, Texas A&M University

ucts, and similarly, the twin-screw handles
different products."
Pet food processors must establish operational requirements up front with their
equipment suppliers about their goals so the
extruder can get the job done in an optimal
way. These conversations, as well as testing
the raw materials on suppliers' equipment,
will help pet food processors get a clear
picture of what extrusion system and components will work best for their products.
"This will determine overall screw length,
screw elements for best mixing and cooking,
and functionality of control systems to proportion ingredients and liquids while fine
tuning speed and temperature," says Dave
Carney, area sales manager, Buhler, Cary,
North Carolina.
Whether or not the product will be raw
or cooked is also an important distinction
processors need to make to extruder suppliers, as extruders can do both. "I need to understand if a customer wants to portion the
extruded product as a raw product or if they
want to portion the cooked product," says Jay
Wenther, Ph.D., director of meat technology,
Handtmann Inc., Lake Forest, Illinois. "This
assists in determining what extrusion may
work for them and be the most economical
for their business."
While most pet food is made in singlescrew extruders, that may not be the best
hardware to process high protein treats and
food that is growing in popularity. "Some
products can't be made on a single because
a twin-screw extruder can handle very viscous, oily, sticky materials," Riaz says. "We
use a twin screw when you need high proPet food processors should know the finished product
and volume they require; the shapes, sizes, desired
textures and the raw materials they'll be working with
from the outset.



tein, high fat or high moisture."
As the protein level in a recipe is increased - usually at the expense of starch -
there are changes in product expansion, texture and durability. Rokey explains, "Higher
protein levels usually result in less expansion as many proteins are less viscoelastic
than starch. Increased levels of protein usually result in firmer or harder textures compared to starchy recipes. Many proteins are
not functional, in other words they will not
contribute to expansion and binding in the
extruded product matrix. Generally, products made using recipes with higher protein
levels will have less durability and may break
and generate fine dust during handling and
Clextral gives pet food processors the
ability to test their products on Clextral extruders at one of two research centers, one
in the US and another in France. At these
centers, Clextral's customers can develop
and test new formulations and take advantage of the company's mechanical, electrical
and automation training services. First and
foremost, though, pet food processors can
have the opportunity to test all the different
components Clextral offers on its extruders
to find the appropriate hardware for their
products. "Clextral provides many options
including specific die designs for innovative
shapes and special knives that are able to cut
highly viscoelastic products in a very consistent process," says Alain Brisset, Clextral
SAS, Firminy, France.
Beyond the actual machine, it's important
that the production line matches the throughput a pet food processor expects. Over-sizing
the line is not always the best strategy for expansion and can potentially hinder the line
from running at its best. "Instead of buying
a larger capacity and only running it half
the time, buy a line for five tons and run five

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