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Pet food coating
Snack coating
Vegetable casing extrusion
Coating of pet food with digest and palatant
A pet food is generally a cereal-based protein-enriched ready-to-eat feed for cats and dogs. Palatability is key to pets' acceptance.


The core is made of a pre-cooked and expanded cereal and protein mix (corn, wheat, rice, potato, meat meal, fresh meat and fish...). Expansion is direct (high pressure short time extrusion). The resulting bulk density is medium : 0.2 to 0.5.


The liquid coating is prepared with:
  • vegetable oil,
  • digest (resulting room the microbial digestion of meat by-products),
  • minerals and vitamins.
A dry seasoning can be further applied:
  • cereal carrier ,
  • flavour mix.


The coating sequences run as follows:
  1. consistent dosing of the pet food,
  2. liquid dosing and dispersion, often air-assisted, + 5 - 30%,
  3. powder dosing, +1 - 10%.

Coating system

The operation occurs usually in a rotary tumbler or rotating swcrew whose length and diameter are calculated to accomodate the product flow.
The coating relies on dispersion of the liquid and powder ingredients first, then on the mechanical friction caused by mixing.
Liquid and powder ingredients can be added separately. One option is to mix finely ground spice powder into the oil and carry out just one application. This 'slurry' needs to be constantly agitated until it is applied.
Ingredient dispersion can be enhanced by blowing air. Liquid ingredient are best dispersed by dedicated spraying systems.
Powder can be dispersed with a vibratory tray .br> It is a continuous operation. Rotation speed (and tumbler tilt angle) are adjusted to achieve the required friction and residence time. The residence time is relatively long to allow for the absorption of a large quantity of liquid and powder ingredients.
For the same reason, an alternative technique consists in a dual shat paddle mixer. The sequence runs as previously described but as a batch operation. Due to the efficiency of the mixing a whole cycle from loading to discharge takes a few minutes. Being an enclosed process, vacuum can be applied prior to ingredient addition to enhance the absorption during mixing.

Key parameters

Summary :
  • machine length, diameter and accessories design,
  • product rate, liquid and powder relative rates,
  • rotation speed.
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Picture of pet food, courtesy of faqs.org
Diagram of pet food coating
Pet food coating mixer, courtsey of Dinnissen
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