Mixing quality

Increasing demands

According to the Alltech Global Feed Survey, dry pet food production reached nearly 25 million metric tonnes in 2016, with a global pet food production increase of 10.6% over 2016. To satisfy increasing demands, production capacities in pet food plants are often pushed to the limits. But quality should not be compromised. 

Homogeneous diet

Mixing is one of the most essential operations in pet food production. Only a homogenoeus diet will provide all necessary nutrients to pets. Excess variability in diet composition can have adverse effects on process parameters, and product quality as well as on pets’ health. If mixing time is longer than optimal, production capacity of the mixer is decreased, which eventually may decrease the capacity of downstream equipment. Also, a prolongation of mixing time can cause de-mixing of dry mixes, with additional use of labour and energy. On the other hand, if dry blends are not completely mixed, portions of pet food will deviate from prescribed formulations. 

In practice, it is impossible to obtain ideally homogeneous mixtures. Coefficient of variation (CV) is the parameter usually used for evaluation of mixer performance and mixture uniformity. Lower CV values indicate that mixtures become more homogeneous. Mixing time should be determined individually for a combination of specific mixer, specific mixing parameters and specific mixture. Therefore, besides periodically routine testing, mixer testing is both economically and ethically justified, for any change in mixing processes.

Risk of carryover

Besides mixing homogeneity, pet food producers should pay attention to carryover in their plant. Carryover is the contamination of material or product with another material or product that originates from previous use of equipment. Carryover can occur in different parts of the plant, so specific constructions of equipment combined with regular equipment inspection and cleaning, are required to prevent carryover in pet food plants. This enables implementation of corrective measures for minimizing contamination risks.

Quality and quantity

Nowadays, regulatory authorities in many countries are increasingly concerned with ensuring that all micro ingredients are added in pet foods as formulated (homogeneous diets), without residues from previous batches (no cross-contamination). 

Various substances have been used as tracers to measure feed mixing efficiency. However, experimental determination of carryover in the pet food plant cannot be carried out by means of real additives, due to high dispersion of the analytical results. Thus, instead of additives, indicator substances (tracers) are used. For example the coloured iron tracer particles (Microtracers™), which can be magnetically separated from the formula feeds, have successfully been used in practice for both homogeneity and carryover testing. 

Pet food producers must take responsibility to provide quality products to pets, by implementing quality control procedures, among others. In accordance with legislation, the proof of the mixer performance and working accuracy of the plant are key points for proving process quality in pet food mills. However, improving production quality must not compromise the quantity of products supplied.