PET Food Processing - June 2018 - 55



Baking and drying technologies deliver critical
moisture uniformity to pet foods and treats.

By Jennifer Semple |


Fine tuning the baking and drying parameters to produce reliably uniform, shelf-stable pet foods and treats
depends on more than time and temperature. The density and ingredients specific to pet formulas make removing moisture a challenge. Ovens and dryers work in
tandem to provide the needed process controls for repeatable results.
The basic thermal process is the same for baking
and drying. In baking, the primary purpose is to bring
about a chemical or structural change to the product,
and moisture reduction is a by-product. In drying, the
primary purpose is to remove moisture. "Both processes use temperature and airflow for some given product
retention time to get the desired product," says Tom
Barber, vice president of process engineering at Bühler
Aeroglide, Cary, North Carolina. "They use convection
airflow for the heat transfer and moisture removal. The
differences between ovens and dryers relate to operating
temperature, process air velocity and distribution, process air humidity, air exhaust volumes, product depth
and conveyor speed."
Baked products, such as dog biscuits, go through
three distinct thermal processes. The dough is baked
after forming to set the structure, then the baked product must be dried to a shelf stable point and adequately
cooled before packaging or storage to prevent moisture
condensation. "Ovens normally do not have a high exhaust rate, so it takes higher temperatures and longer
retention times to get the final moistures low enough,"

Barber explains. "The high discharge temperatures on
the product also make it difficult to cool the product,
requiring long cooling retention times. The dryer has
a much higher exhaust air exchange, allowing drying
at much lower temperatures and in a smaller piece of
equipment compared to an oven."

Innovative dryer
technology provides
feedback information to fine tune the
drying process.
Bühler Aeroglide

Moisture matters
The two major types of products in the pet food industry are formed baked products and extruded products.
The equipment used for these processes is similar to the
human food industry. "For baked products, the dough
structure is set in the oven, and the final baking yields
a crisp product with some browning and flavor development," Barber says. "Sometimes all of this is accomplished in the same oven, but the process may also require a post-bake dryer to more efficiently reduce the
moisture content of the product."
Dog biscuits or treats come in a range of sizes.
Achieving target moisture levels are important to obtain the required shelf life. Most baked pet treats contain 30% moisture leaving the rotary moulder, 20%
leaving the oven and just under 10% leaving the dryer.
Sam Pallottini, director of cookie, cracker and pet
food sales, Reading Bakery Systems (RBS), Robesonia,
Pennsylvania, says, "The challenge is to not case harden
the larger products. Once the product is case-hardened,
it becomes impossible to achieve the desired moisture
levels. Increasing bake time and reducing the airflow in | June 2018 | PET FOOD PROCESSING


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