COLD EXTRUSION
Protecting Nutrient Integrity for Dog (and Planetary) Health
Diet is the most important aspect of our pet’s health and wellbeing.
Unfortunately, most of us assume that the food we’re feeding our dogs is abundant in all of the nutrients that they need to need to flourish and thrive, however, by its very design, food processing significantly alters the form of food from its raw state and is well-known to negatively impact the nutrient content of foods.
Extrusion is one of the most commonly used food manufacturing processes. Its versatility enables production of a diverse array of food products many of which we consume everyday - pasta, breads (croutons, bread sticks, and flat breads), breakfast cereals, baby food, pet food, texturized vegetable protein, premade cookie dough, baby food, processed cheese and more.
Originally developed in the 1930’s, extrusion was used to produce dry pasta and breakfast cereals. In the 1950s, it was used to manufacture pet food. Over the next 90 years the applications of extrusion processing have grown as the technology made the texturization, mixing, forming, and cooking of food simpler, more economical and more uniform.
There are multiple types of extrusion processes depending on desired format and characteristics of the end product. The four main extrusion types used in food manufacturing today are:- cold, hot, steam-induced and co-extrusion.
The basic process of producing all extruded food is very similar - heat and mass transfer; kneading and mixing; micro-mixing ingredients; and chemical reactions, cooking, and texturization.
The steps used in extrusion follow a process where ‘dry’ ingredients are first ground to the optimum particle size, generally the consistency of a coarse flour. The dry mix is passed through a pre-conditioner, in which other ingredients are added depending on the end product; these may be vegetables and fruits, oils and fats, meat or water. These form a preconditioned mix of all the raw ingredients, called the extrudate.
Steam is often injected to start the cooking process, and the extrudate is then passed through an extrude, a large, tight-fitting, rotating screw within a static barrel. At the end of this barrel is the die. The rotating screw forces the extrudate towards the die at a predefined pace depending on cooking time required for the end product.
Cooking takes place within the extruder, as the product produces its own friction and heat due to the pressure generated. The process can induce both protein denaturation and starch gelatinization in some conditions.
When the extrudate is forced through the dies it produces the desired shape of the product – cereals, baby food, dog food, popped and puffed snacks – extruded products often expand and change texture as they are extruded because of the reduction of forces and release of moisture and heat.
Approximately 95% of all dry dog food, kibble and biscuits, are processed using what is called a ‘high temperature short time’ (HTST) extrusion method. This process heats the ingredients to temperatures of between 110ºC to 150ºC for between 60-270 seconds. Although little research has been undertaken on pet food, what has been done shows high temperature processing to be the most impactful on your dog’s food’s nutrient integrity (1,2).
High temperature processing has particular impact on non-heat stable vitamins, effectively reducing the levels of vitamins requiring dog food manufacturers to add back excess vitamins to ensure your dog gets the vitamins they require. Those most effected vitamins are the B group vitamins, vitamin A, vitamin C and vitamin E (4). While minerals are less affected by heat it can affect bioavailability, meaning that your dog may not be receiving as much of the mineral as they should be for their optimum nutrition and health (6).
Essential fatty acids, including the very important, and healthful, Omega 3, have been shown to be negatively affected by increased processing temperatures (7).
Probiotics, which are known to improve your dog’s gut health and microbiome, are also shown to be highly heat sensitive and their efficacy in optimising your dog’s gut, and overall health, is greatly degraded by high temperature processing (8).
Finally, protein, which is the very foundation of your diet and your dog’s is also affected by the processing temperature.
Increasing heat denatures protein and also results in the triggering of a chemical process, the Maillard reaction – the browning process of meat and other foods caused by heat. This leads to the formation of numerous toxic compounds including acrylamide and advanced glycation end products (AGE’s), both of which have been linked to a multitude of different disease state - including cancer, in people and dogs.
From an environmental perspective high temperature cooking requires a considerable input of water (in the form of steam) as part of the process. This together with the increased levels of energy required to generate the high heat levels results in greater greenhouse gas emissions significantly adding to the environmental impact your dog’s food has.
In contrast cold extrusion, while using a similar process to premixing ingredients to create the food for extrusion, is gently cooked at temperatures not exceeding 70ºC, one of the primary advantages of cold extruded foods. Because of the gentle heat used during the cooking phase of the cold extrusion process, it can be used to prevent heat sensitive ingredients such as vitamins, minerals, omega-3 essential fatty acid, phytonutrients from plant-based ingredients including herbs and botanicals and probiotics, from degradation.
As vital nutrients are not subject to the high levels of mechanical shear and temperature ingredients are exposed to through the HTST heat extrusion process, nutritional integrity is optimised and the requirement for added synthetic nutrients to compensate for damage caused by heat is minimised.
Importantly the lower use of energy, water and miscellaneous inputs means lower emissions and less impact on the environment overall. A greater quantity of ‘wet’ ingredients can be used allowing for the inclusion of more fresh ingredients. This cooking method also results in a lower level of lipid oxidation, making the final food more nutritious.
Cold extrusion dog food – good for your dog, better for the planet
Good. Better. Bonza.