Are canned and packaged foods on the shelves at the supermarkets marked with the date of processing? Is there a dating code used on boxed or cartoned foods? These are questions homemakers are asking. Most packaged (canned, boxed, cartoned) foods are produced in tremendous quantities by the food industry and marked with codes for purposes of identification. It is most desirable that all containers of one batch be identified to prevent mixup during warehouse storage, transportation, and marketing. If any defect in processing or formulation were to occur, it could then be isolated. With raw fruits and vegetables, the raw product quality may vary with climate and other conditions. With coding, the “best” quality may be separated from the “better” quality. Several codes may be used each day or there may be just one code for the day’s processing.

One supermarket chain indicated recently that it would reveal what its codes were. How would understanding the code be helpful to the consumer? Knowing the code would not tell the whole story. It would tell only one thing—the date the food was placed in the container.

But other vital information is revealed by the food in the package. The homemaker should be aware of such points as these: (1) Does the food have a normal, inviting color? (2) How does the food taste when you prepare it? (3) Is the texture acceptable? (4) Is the food nutritionally valuable? The first three questions are best answered by the ones who prepare and eat the food, and are not necessarily related to nor often much affected by the date of packaging. The nutritional value of the food is not readily evident (it may be listed on the label), but it is generally related to the quality of the color, flavor, and texture.

Whether the end product is buttered green peas, angel food cake mix, or fish sticks, the food quality depends on the raw materials. The quality is not improved by processing; most often it is partially destroyed. The nutritional quality of the processed food will depend on the variety of the fruit or vegetable, its maturity, and the freedom from disease and pests before it goes into the container. The actual processing of the food will have an effect: for example, blanching green beans or peas too long leaches out flavor, standing after blanching affects color and texture, too much chlorine in the water changes flavor, and overcooking is undesirable.

The main reason canned fruits and vegetables do not taste like those freshly cooked is because sterilization is used, requiring very high temperatures for twenty to thirty minutes. This causes rapid changes in color, flavor, texture, and nutritional value. New methods of processing that employ a higher temperature for a shorter time can sterilize the food and maintain more of the quality.

Quality of food may also be expected to deteriorate slowly with storage because of time and temperature. A good temperature for storage of canned food is 50° F., which is almost refrigerator cool. An increase of 20° F. approximately doubles the rate of deterioration; thus, food stored at 70° F. will deteriorate twice as fast as food stored in 50° F. Since 50° might be difficult to maintain, you can store foods over a long period at 70°. Storage at 90° F. is highly undesirable, as it promotes rapid deterioration.

Values for shelf life at 70° F. reported by the U.S. Army’s Quartermaster Corps (1951) indicate that canned fruits and vegetables may reasonably be stored for extended periods of time. Low-acid fruits such as pineapple, peaches, fruit cocktail, grapefruit, apples, and pears will keep for thirty-six months, while highly colored, high-acid fruits such as blackberries, blueberries, cherries, cranberries, and plums will retain quality for twelve months or more.

Low-acid vegetables such as beets, cauliflower, squash, sweet potatoes, and tomatoes may keep for more than four years, while peas, corn, and lima beans may keep for as many as eight years. Asparagus, carrots, green beans, and spinach were reported to keep for three years or more.

During these long storage periods quality is slowly being lost, which suggests that for stored foods in general, it is best to eat and replenish them as soon as it is practical. When buying food, how it looks, how it tastes, and how it feels in the mouth, as well as its nutritive value, are the best indicators for repeat purchases and the best bases for making case-lot purchases.

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  • Dr. Johnson is chairman of the Department of Food Science and Nutrition at Brigham Young University. A former bishop, high councilor, and missionary, he now serves the Church as teacher development director in Benjamin Ward, Palmyra Stake.