Pet Food Manufacture

In this series, we have discussed how pet food is tested for safety and quality and we have covered the ingredients and labeling of pet foods, but we have not reviewed the actual process by which pet food is manufactured.

Prior to the commercialization of pet foods, people fed their pets table scraps, leftovers, or meat scraps purchased especially for pets. In addition, pets were generally allowed to hunt and forage for themselves. There was very little control over nutrient content and balanced diets were achieved only by coincidence. Parasitism was much more common due to the prevalence of raw meat in the diet as were food-borne toxins.

The first commercial pet food, called dog cake, was produced in 1860 by James Spratt in an effort to improve the overall quality of what was being fed to dogs. His company thrived into the 1950s when it became part of General Mills. In 1907, F.H. Bennett introduced Milkbone dog biscuits, not as a treat but as a complete dog food. These two companies dominated pet food manufacture until the 1920s when canned dog food was introduced by Ken-L-Ration. By 1941, canned dog food represented 91% of the dog food market but this reversed during World War II as tin was felt to be an important resource in the war effort and by 1946, dry foods became more popular. Kibble as we know it today appeared in 1957 when the Purina company began marketing dog chow and cat chow. Today, the pet food industry is booming with sales increasing annually. We all like the convenience of buying a pet food already prepared, easy to store, proven to be nutritionally balanced, and safe.

But one has to admit that the kibble poured into our pet's food bowl bears little resemblance to the meat, corn, and wheat from which it started out. The rest of this article reviews how we get from the ingredients we might recognize in our own refrigerators to something that can be stored in a bag without refrigeration for months.

The Manufacture of Dry Pet Food

Commercial preparation of pet food must meet a spectacular demand: over 12 tons of food hourly. This must be done in such a way that each batch is nutritionally and flavor-wise identical to every other batch. Precise weighing and inspection are critical. The process by which the food product is put together in this controlled fashion is called compounding.

Ingredients are purchased by the truckload. This includes dry meals, sacks of vitamins and minerals and meats.

Dry ingredients must be ground to a specific particle size. The size of the particle will determine the water absorption of the dough, how it cooks, and how it will appeal to the pet. A machine called a hammer mill is used to grind the dry ingredients to the right size. The resulting mixes will look like flour.

Next, the ingredients are mixed together specific amounts and mixed together. Computers control the weights of dry ingredients used. A machine called a ribbon blender is used to thoroughly combine the dry ingredients.

Next comes the preconditioning stage

where the dry and wet ingredients are mixed. This is where meats and fats are added in along with steam to begin the cooking process. After about one minute, the mixture is ready for extrusion, which is where the main kneading and cooking portion take place.

 

 

The machine is called an extruder

and looks something like a screw inside a barrel with the food passing through the threads of the screw from one end to the other. The food cooks as it contacts the barrel wall and changing the screw's turning speed can alter the character of the food. In general, higher temperatures and fast speeds through the extruder are used as these produce more complete cooking and destroy toxic microorganisms the best.

After extrusion, the food is a spongy dough. It is forced through a die at high temperature and pressure so as to create the kibble shapes we are used to seeing. The dough hits room temperature where two important events occur: moisture flashes out of the kibble and the kibble expands about 50% in size. At this point, the kibble is still quite hot and soft.

The final stage is enrobing. The food is cooled in dryers and sprayed with an external coat. The extrusion process inherently destroys some nutrients (vitamins A, E, and B1 are especially susceptible). These nutrients are sprayed back on to the kibbles to ensure their proper nutritional completeness. Often the spray includes special added flavorings (like the Gravy Train coating, for example).

From here, the food is weighed, bagged, and sent to local grocery and/or pet food outlets for us to purchase.

The chief source for material in this article was "Making Commercial Pet Foods" by C.S. Cowell, N.P. Stout, M.F. Brinkman, E.A. Moser, and S.W. Crane in Small Animal Clinical Nutrition by Hand, Thatcher, Remillard, and Roudebush, 4^th edition, Walsworth Publishing Company, 2000.