IMAGINE strawberries that stay fresh for 2 or 3 weeks, pork that doesn't need extra long cooking, chicken, shrimp, and vacuum-packed meat that can be kept outside the refrigerator for six to eight years. These are some of the promises of food zapped with radiation to preserve freshness, to kill insects and bacteria, a process that could become as common as canning, freezing, or microwaving by the year 2000, according to Prof. Richard Matthews of the University of Florida's Institute of Food and Agricultural Sciences.
But this rosy view is not unanimous.
Last month when a supermarket in North Miami, Fla., offered Puerto Rican mangoes that had been treated with gamma rays, it set off questions and controversy.
Although exposing some fruits and vegetables to low doses of radiation was approved by the United States Food and Drug Administration (FDA) in April, the process has been used mainly for spices and seasonings, until the recent sale of the irradiated mangoes.
``The food treatment process is simple,'' explains Dr. Matthews. ``Foods are put on a conveyor that exposes them to radiation inside a shielded chamber. Gamma rays from cobalt 60 or cesium 137 can be used, or foods can be exposed to X-rays or high-velocity electrons.''
Matthews cautioned that once exposed to these low doses of radiation, foods must still be refrigerated or handled like regular foods not treated with radiation.
It was more than 20 years ago that the FDA approved the radiation treatment of wheat, wheat flour, and potatoes. Dried spices and pork were given the OK in the 1980s. Other countries around the world have been selling some irradiated foods for years, but so far there has not been much available in the United States.
The major consumers of irradiated foods have been servicemen and astronauts on NASA's space shuttle, which has no refrigeration or cooking facilities.
Vacuum-sealed, irradiated steak, which could last two to three years, as well as irradiated rye bread, rolls, and other foods have been served aloft. Other consumers include hospital patients diagnosed as having low resistance to infection.
Overall, the commercial development of the food-irradiation process has been slow. But this is nothing new. American consumers have frequently been hesitant about accepting new food techniques.
It took more than 50 years for the canning process to become fully accepted and years for people to become accustomed to frozen foods.
``Irradiated foods are probably not going to make a big hit with most people right away,'' says Dr. Matthews.
``At best, consumer acceptance will be slow. And I believe the food industry itself will be conservative about adopting this new technology.''
Radiation is a scary word. The public winces at the thought of eating anything treated with radiation, even though scientists say there's no radioactivity created in food from the process.
Because it will extend the shelf life of certain foods, the new ruling is seen by some as a great service to consumers. Others, however, consider the practice of irradiating foods to be expensive, unsafe, and unneeded.
In spite of the FDA's approval, the process until now has been used mostly to preserve herbs and spices. But recently.
When irradiated mangoes appeared in Laurenzo's Farmer's Market in Miami Beach, owner David Laurenzo explained that fruits such as mangoes and papayas have been difficult to find in the US.
``We wouldn't be able to import Puerto Rican mangoes if they weren't treated,'' Mr. Laurenzo says. ``I believe it's a safe, good way to preserve the fruit a few days more.''
``Treated food can be eaten immediately,'' says George Giddings, director of food irradiation at Isomedix Inc., a company with plants in several cities and in Puerto Rico. ``It is absolutely impossible for any radiation to be still in the food -- the same as a radiation treatments to the human body. After it's over, it's over.''
``The radiation penetrates through the food and its packaging so that all portions are treated. No residues remain,'' Mr. Giddings says. ``There is essentially no temperature rise in the food. Frozen frogs legs and shrimp will not thaw while being decontaminated.
``The molecular changes that occur in foods at the FDA-approved one-kiloGray level are minimal: less than those that occur when foods are cooked or canned. The change of color and flavor of various spices are less than from fumigation, '' he says.
``The other day I opened a package of ham that was 14 years old and ate it on camera,'' Giddings says. ``It was delicious. I am convinced that it won't be long before products such as meat will last for many years with no need of refrigeration.
``The containers will be vacuum-packed and the food sterilized. And there will probably be more technological advances. It might soon be possible to preserve bacon, for example, without the use of additives known to have an association with cancer.
``In South Africa, which has two private plants, strawberries are irradiated and then shipped to markets hundreds of miles away, where they command premium prices for a longer period than untreated berries.''
Twenty nations have approved the use of irradiation of foods, some up to the 10 kiloGray level, on products such as frozen shrimp, frog legs, chicken, papaya, mangoes, strawberries, dates, onions, potatoes, bananas and rice.
Critics object, among other things, to the labelling of irradiated foods. They question the safety of the food when eaten and they say the benefits of of the process have been exaggerated.
``The consumer is not going to be able to tell whether a food is irradiated or not,'' says Ellen Haas of the Public Citizen Health Research Group in Washington, D.C. ``Although labelling is required now, in two years only a stylized flower logo will be necessary.
``Fruits and vegetables haven't been labelled in the past as to nutrient value,'' she says, ``so it will be doubly hard to figure out a way to give information about irradiation for produce.
``I'm concerned, too, about the fruit in mixtures such as fruit cocktail. Some fruits may be irradiated -- such as cherries -- and others not. Labelling is essential. It's a basic consumer protection, and consumers must have that information in order to make correct choices.''
The question of nutrient loss is another point of controversy.
``There have to be significant losses of food value,'' says Ms. Haas, quoting a test that showed that Temple oranges lost 28 percent of their Vitamin C through being irradiated.
``People may buy fresh foods that have been irradiated and later freeze them at home, which would result in multiple loss of nutrients,'' she says. Food loses nutrients every time it is processed, whether in canning, freezing, or cooking.
``We're not saying it is a hazard, but that the government has not done enough testing. The benefits are exaggerated. I think the government is moving too quickly,'' she says.
Merle Eiss, information systems manager at the McCormick Spice Company, says nutritional quality is not a big problem with herbs and spices.
``We must realize that just about everything done to foods, including harvesting, results in some nutrient loss. Because irradiation is a cold process, as opposed to the traditional heat processing, it is generally more gentle than traditional processes and leaves the final food closer to fresh. We have tested and used various methods, and we've found irradiation it works well on spices.''
Some objectors are worried about the changes in the balance of food chemistry caused by the altered compounds which radiation produces.
``These changes are not ones a consumer can recognize, because the appearance of the food remains the same -- it still looks fresh. This can be very dangerous,'' says Irving Rothstein of the Coalition to Stop Food Irradiation, in San Francisco.
``I honestly think it's a crime. This is a technology that's not needed. It makes me very angry. It's being foisted on the public . . . . When radiation strikes food, it alters and damages cells. It changes the food as much as it does insects and bacteria.''
``We don't like the idea that the cesium 137 is a reprocessed waste product from the US Department of Energy's nuclear weapons program,'' he says.
In addition to food preservation, irradiation has several industrial applications. Other than sterilizing medical supplies, it is used used to treat the insulation on wire and cable, to cross-link plastic food wrap, and to vulcanize sheet rubber. A proposed use is to disinfect sewage sludge.
At least 10 different agencies, including the World Health Organization and the American Medical Association, have concluded that irradiated foods pose no risk to consumers.
The US Institute of Food Technologists, for which Dr. Matthews is the spokesman, is conducting a public education campaign on the process.
Phyllis Hanes is the Monitor's food editor.