Pet Food Canning

In the last installment of the Nutrition Corner, we reviewed the production of dry food. This time we review the production of canned food.

The canning of food is a 200 year old process of nutrient preservation and was performed centuries before anyone had any knowledge of food poisoning bacteria. Moisture in food is normally an invitation to bacterial colonization but through canning and its associated vacuum and high temperatures, wet foods can be kept free of pathogens for long time periods.

Here’s How It’s Done:

STEP ONE:

Animal proteins either fresh or frozen are ground and mixed together.

STEP TWO:

The meat mixture enters a “cooker” which is responsible for determining the ultimate texture of the food. The meat is mixed with grains, vitamin and mineral supplements, and water and all the ingredients are cooked together at a specific temperature which will yield the desired final consistency.

STEP THREE:

At this point, the food is still quite hot and moved to the “filler/steamer” machine which will fill 300-600 cans per minute. After a can is filled, steam is injected over it which displaces air. As the steam cools, the water vapor condenses to create a vacuum as the can is sealed. This is the step that controls the safety of the food. The creation of the vacuum is dependent on the cans being filled properly.

STEP FOUR:

The can has been sealed and is moved to a sterilizing machine called a “retort.” The food product will not be rendered completely sterile in a literal sense but will be rendered sterile of bacteria known to cause disease. A temperature at the core of the food in the can must achieve 116º F for 60-90 minutes. This temperature is not high enough to continue cooking the food but will be enough to kill bacteria. The cans are then cooled.

STEP FIVE:

The heat from the retort dries the outside of the can in preparation for labeling. The can is scanned electronically to ensure proper sealing. The cans are stamped with a date signifying the production date and adhesive and paper label are applied. Cans are then packaged into cases for distribution.

Canning allows for a more palatable food. Gravies and jellies are created by adding gelling agents to the ingredient list.

The point is that canning is not some kind of mystical process which involves heavy processing or removal of nutrients. Canning is an excellent method of food preservation when food moisture is desirable. The food material is not particularly different from that in dry food; it is simply prepared in a different way to yield a different consistency.

Information for this article can be found in: Cowell, C.S., Stout, N.P., Brinkmann, M.F., Moser, E.A., Crane, S.W. Making commercial pet foods. In: Hand, M.S., Thatcher, C.D., Remillard, R. L., Roudebush, P. eds. Small Animal Clinical Nutrition 4^th Edition, Marceline, Missouri: Mark Morris Institute, 2000; p135-138.

HUNGRY FOR MORE NUTRITIONAL INFORMATION?

We recommend the following web site which contains basic information about pet food, nutritional counseling, food calculators to compare food, and more. It is run by Dr. R. Remillard (one of the editors of the chief text used for this series and nutritionist at Angell Memorial Animal Hospital in Boston).

Please visit