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 acceptance by choosy pets

Updated Aug 08, 2021 - 10 min Read


Core products

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


How does it work?


The core products are formed by extrusion or – for more sophisticated treats – through a bakery process. Drying is compulsory.


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.


After coating, the product is ready for packaging

The coating phase runs as follows


Consistent dosing of the pet food



Liquid dosing and dispersion, often air-assisted, + 5 – 30%



Powder dosing, +1 – 10%


Coating system

The operation occurs usually in a rotary tumbler or rotating screw whose length and diameter are calculated to accomodate the product flow.
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 .

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 shaft 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. 


Coating system

Given the large volume processed, the coating system is a combination of the main coating system with liquid and powder applications devices, themselves fed with preparation, mixing and handling assemblies


How do you measure your success?

Key quality features

The true evaluation is reverted to the pet consumer and assessed by physical values


Crunchiness vs. softness measured by instruments and sensory evaluation


Appealing formula vs. cost, completedwith sensory evaluation tests wih pets


Adsence of residue, fine or off-flavour over time

Key quality parameters

Pet food coating is a specific domain of food processing


Flavour selection is a matter of specialized suppliers


Machine design, volume, accessories


Mechanical energy used for mixing and dispersion. Residence time for impregnation