PET Food Processing - June 2018 - 26


Three hot extrusion lines
from Wenger can produce
kibble, long goods, semimoist products, dental chews
and co-extruded chews.


screw extrusion and thermal twin screw extrusion.
Single screw extrusion - the Wenger X25 - produces
less complex pet foods at economical production costs.
This would include low fat, low meat products and other
products with a narrower range of ingredient flexibility.
By changing the extruder screw configuration, the X25
single screw extruder is a good machine for making regular brown and round kibble for dogs and for cat food as
well as simple soft moist treats with humectants added
to prolong shelf life.
Twin screw extrusion - the Wenger TX85 - is the
system of choice for pet foods above 7% internal fat, up
to 70% meat and sizes that are less than 1.5 mm or greater than 25 mm in diameter. The TX85 is also equipped
with a Density Management System (DMS) to make fully cooked but unexpanded chew treats that have dental
attributes. The self-wiping, intermeshing screw profiles
of the twin screw design permit a broad range of recipes including those that would be so sticky they would
build up in the single screw design. This system utilizes
mainly shear or mechanical energy (friction) to cook
and is limited on how much thermal energy (steam) can
be used in the extrusion cooking process.
Thermal twin screw extrusion - the Wenger TT760
- can utilize mechanical energy or thermal energy to
cook a product. The thermal twin design allows much
higher levels of steam inclusion to shift the cooking process from mechanical energy inputs to thermal energy
inputs which results in lower wear costs, lower energy
costs and a broader range of final products. The thermal
cooking process of the thermal twin system reduces the
stickiness of starches in pet foods compared to when the
product is cooked with shear. This reduces many pro-


cessing challenges when processing pet foods - especially the grain-free diets.
The Wenger thermal twin line at Pedigree Ovens and
The Pound Bakery can also deliver product directly to
a baking oven to produce extruded, baked products.
"Coupling extrusion with the baking process yields a
unique pet treat product that has improved palatability
and textural attributes not found in standard pet products that are extruded and then dried," Rokey adds.
Not only does the extruder design contribute to process flexibility, but the complete line downstream of the
extruder can have an impact on what products can be
manufactured. "The thermal twin line offers pneumatic
conveying of product directly off the extruder die which
can be introduced into the Wenger Air Flow II dryer
cooler or it can be diverted into the Reading Bakery
Systems oven to get a baked appearance before going to
the Wenger dryer to finish the moisture removal process," Rokey says. "With the addition of the TX85, Kurt
has another avenue of product capability for long goods."
Long goods involve a process line where the product
comes off the extruder in ropes which are conveyed directly in to a cooling tunnel to set the linear structure
and then are cut to the proper length with a Reading
Ultra-Sonic Guillotine Cutter. Many pet treats require a
dense, chewy texture to impart dental attributes and the
DMS added to the TX85 permits this type of processing. This machine can do anything in the range of a direct expanded snack treat up to long goods such as jerky
strips and ropes.
Finished product leaves the hot extrusion room on
Meyer conveyors and travels to the packaging room
where product can either go into holding tanks or to one
of several different packaging machines. The three holding tanks from MacProcess allow Pedigree Ovens and
The Pound Bakery the flexibility to mix different percentages of the three products from the holding tanks
into packages.
Compared to the company's baking capabilities,
Stricker says the hot extrusion room has much greater
capacity, but that's not how they'll use the extruders.
"Hot extrusion is new for us and the output is so much
higher than baking. Those two new Wenger lines could
produce 100,000 lbs. per day total, but we'll never use
that capacity because we're not just doing kibble; that's
where you get that output." The company has a few initial contracts for denser sticks and pieces, which can
have a much slower output rate of 2,500 lbs. per hour.
"One thing we know we want to produce is an extruded stick with a better ingredient panel, less salt, fewer
preservatives and less sugar," Berglund says. "We want
to take extruded products and clean up the label, just
like we've always done with treats. People are conscious

Table of Contents for the Digital Edition of PET Food Processing - June 2018