Food Freshness : Food Preservation

by Food and Drug Administration (FDA)

(Page 3 of 3)

"After succeeding in this endeavor," says Casciano, "he theorized that the physical characteristics of the molecules in the new carpeting were similar to those in spoiled fish." Miller explains that the odor from both the carpet and the fish is known as a "volatile," a material that at normal temperatures or under the influence of heat is capable of being vaporized or becoming a gas. "If you can smell the odors," says Miller, "they're in the gas phase."

Casciano says that Miller shrunk the original desk-size analytical detection device used to test the carpet vapors down to what is now a quarter-sized food quality indicator designed to be inserted into food packaging.

The technology behind the disk is based on a dye locked in a water-repellent material and used as a dot-shaped chemical indicator that changes color as a seafood product decomposes. As the gases from the seafood move through the dot and intermingle with the chemicals, a gradual color change is produced in the disk when a sufficient level of the chemical is present.

At the supermarket, food quality indicators and other products using similar technologies would allow consumers to make rapid and informed decisions on food quality.

But Susan Ferenc, Ph.D., senior scientific adviser to the Grocery Manufacturers of America, a trade association in Washington, D.C., is somewhat skeptical.

"Unless it is very clear as to what these disks indicate," she says, "my thinking is that consumers are going to be a bit cautious — and should be, especially given the number of false positives or false negatives that could come with the technology."

At the regulatory level, Miller says that insertion of these indicators in fish products at the point of origin (during processing and packaging) could help FDA inspectors rapidly identify fish products that have deteriorated beyond acceptable limits, helping to speed inspections.

The freshness detector system is being tested on shrimp in Canada and the results are very promising, with consumer use expected to follow. But, says Miller, "Since some foods don't decompose by the same mechanisms, the technology still has a way to go." As various toxins become characteristic of one product and then another, the idea will continue to be refined and adapted. Variations are being developed to monitor the freshness of poultry, meats, carbohydrates, and powdered baby formula.

All the new technologies in the world won't make a difference, says Ferenc, if other tried-and-true measures aren't routinely practiced. In short, regardless of technology, consumers need to choose food products carefully and handle and serve those products with care at home.

Food Preservation

All foods eventually spoil if not preserved. The basic idea behind the different forms of food preservation is either to slow down the activity of bacteria, or to kill the bacteria altogether. In certain cases, a preservation technique also may destroy enzymes naturally found in a food that cause it to spoil or discolor quickly. Some of the most common methods for preserving foods are:

Refrigeration and freezing: Slows bacterial action so that it takes food much longer (a week or two, rather than half a day) to spoil, or stops bacterial action altogether. Once a product is thawed, however, the bacteria can become active again, multiplying under the right conditions. Enzyme activity is slowed down but not stopped during freezing.

Canning: Provides a way to store foods for extremely long periods of time. Food is first boiled to destroy bacteria and inactivate enzymes. It is then placed in an airtight container. As the food cools, a vacuum seal is formed that prevents any new bacteria from getting in. Since the food in the container is completely sterile, it does not spoil. Once the container is opened, however, bacteria enter and begin growing in the food. Any unused portions then must be refrigerated.

Drying (dehydration): Removes most of the moisture from foods. This method kills or completely inactivates bacteria. Dried foods should be stored in airtight containers. This process may alter the taste and texture of some foods, but in many cases, a new and better taste has been created. Examples are powdered milk, potatoes in a box, dried fruits and vegetables, pasta, and rice.

Irradiation: Exposes certain types of foods to a source of ionizing energy. Unlike canning, the taste is not altered when food is irradiated.

About the Author

www.fda.gov
FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.