Pet Food Processing / Pet Food Extrusion
On September 9, 2015

Thermal versus mechanical energy in pet food extrusion cooking

Use of high thermal energy provides flexibility, cost savings, nutritional benefits

Complete and balanced pet foods are extruded to provide a shelf stable, resilient, palatable and pasteurized product as a highly digestible delivery mechanism for the essential nutrients companion animals require. 

Traditionally, continuous cooking extruders utilize a combination of mechanical and thermal energy inputs to gelatinize the carbohydrates binding the other ingredients and forming the finished kibble product. Typically, equal-to-higher inputs of mechanical to thermal energy are used to extrude these products. With the continued market trend to increased meat inclusion, unique carbohydrates and product differentiation, as well as the continual rise in energy costs, the use of significantly higher levels of thermal energy inputs has provided a new way of extrusion cooking. Producing extruded pet foods with high thermal energy and low mechanical energy provides operational flexibility, production cost reduction and nutritional benefits over traditional high mechanical energy processing.

Production-related benefits:

1.      Lower energy cost per ton of finished product (see Table 1)

·        Electrical (mechanical) energy costs more per unit than thermal energy.

·        By increasing the thermal to mechanical ratio, the energy cost per ton goes down.


Extruding pet foods with high thermal energy and low mechanical energy has several production benefits, including a lower overall energy cost per ton of finished product.

2.      Lower wear cost per ton of finished product (see Figure 1)

·        Mechanical energy is friction, and friction is wear, so cooking with higher mechanical energy yields much higher wear costs.

·        Typical wear costs is $1.25/ton per 22 kWhr/t of SME.

·        Traditional…

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