Manual of Naval Preventive Medicine
Chapter 1: Food Service Sanitation
Section IV: Inspection of Food Items

1-28. Inspection of Canned Products.

Department of the Navy
Bureau of Medicine and Surgery

1. When inspecting canned products such as meats fish, poultry, vegetables, fruits and juices the following should be considered.

a. Can Labels. Ensure that the contents and processing date are stamped on the label or on the end of the can;

b. Can Exterior. The exterior of the can must be examined for general appearance, dents, swelling, rust and pinholes. Cans having severe dents which cross the ends or side seams or which crinkle the metal to a point (see Figure 1-3) should not be used. Rusty cans may be used provided the rust does not penetrate the can. Rust that can be wiped off is not penetrating. Pinholes are found only by careful inspection.

c. Can Interior. When canned food is suspected of being spoiled, the contents must be removed and the inside of a sample can checked very carefully. It may be necessary to rinse the can thoroughly and then refill with water to detect very small pinholes;

d. Contents of Can. Odor and taste indicate the condition of the food. Fading of color, loss of flavor, and softening of contents may be due to chemical action and natural aging processes. Discoloration may be caused by a chemical action usually found in products containing sulfur compounds such as corn, peas and meat products. Contents of cans with off odor, color or texture must not be tasted.

2. Except for coffee and molasses, which are discussed later, foods contained in the following types of cans are unsatisfactory and must be surveyed.

a. Pinholes. Tiny holes present in cans caused by action of food acids during prolonged storage;

b. Swells or Swellers. Both ends of the can bulge out and remain that way. The condition is caused by action of bacteria (microorganisms) in the foods which result in the freeing of a gas (hydrogen sulfide). This gas cannot escape and gains room only by bulging out the ends of the can. Molasses is an exception. Cans of molasses that bulge at the ends are not unusual, particularly in tropical climates. This condition is normal and should not be grounds for rejection. Microorganisms cannot exist and multiply in an environment so high in sugar content.

c. Springers. One or both ends of these cans are also bulged out, but they will yield to pressure of the fingers or thumb. When the pressure is relieved the ends bulge out again. This condition may be caused by overfilling the can or by chemical or bacterial action on the food freeing gas which caused the swelling condition. Coffee is an exception. Care must be taken not to reject cans of roasted ground coffee showing swell or springer characteristics. Swellers that develop in coffee are usually an indication of a properly sealed container that has retained its natural gases. The gas expands, replacing the original vacuum created in the can. When coffee in a sweller or springer can is of uncertain quality, report it to the food service officer via the senior mess management specialist or the mess sergeant;

d. Flippers. This term describes a can, the ends of which are flat. However, one end may be forced into a convex condition when the other end of the can is brought down sharply on a flat surface. It indicates a loss of vacuum in the can from production of gas by bacteria or by chemical action on the metal of the can. Regardless of the cause, the contents must not be used.

3. Canned food that is abnormal in appearance or odor must never be eaten, or even tasted. It must be discarded. Where large quantities are involved, a representative package must be submitted to a laboratory for bacteriological analysis.

Approved for public release; Distribution is unlimited.

The listing of any non-Federal product in this CD is not an endorsement of the product itself, but simply an acknowledgement of the source. 

Operational Medicine 2001

Health Care in Military Settings

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