Imagine strawberries that would stay fresh for more than a day or two, pork that could be guaranteed free of the threat of trichinosis, salmonella-free chicken and vacuum-packed meat that would keep at room temperature for years. Picture a cornucopia of tropical fruits all winter, fruits that cannot now be imported because of the danger of importing new agricultural pests too.

Such is the promise of food irradiation, a process that some proponents say will revolutionize the way we handle food in the United States.

Food irradiation for commercial purposes has been illegal in this country, but last year the bureaucracy took the first tentative steps toward approval. The Food and Drug Administration okayed irradiation of pork for trichina control, and of fruits and vegetables for insect disinfestation, steps that are almost certain to obtain the necessary approval from the Department of Agriculture in order to become law. Then on Dec. 12, former Health and Human Services secretary Margaret Heckler authorized labeling of irradiated food with the word "picowave," a made-up term that refers to the wavelength of the radioactive gamma rays.

How long will it take before the supermarket shelves begin to sag under the weight of irradiated food? Can we expect a revolution in food handling?

Irradiation can serve many different purposes in food processing, depending on how it is applied and what doses are used. The paradox of irradiation is that levels of radioactivity that could kill a person many times over leave food looking and tasting normal. This paradox is not hard to understand.

Atomic radiation is not all that different from heat radiation, except that the energy comes in much smaller, more concentrated packets. The difference between cooking food and irradiating it is a little like the difference between hitting a car with another car and shooting it through the engine. The crashed car may look terrible, but still run; the shot car may look okay, but not run.

Radiation heats molecules very little, but it energizes the tiny electrons that bind molecules together, loosening the bonds. The molecules fly apart and the pieces desperately try to react with something else. A very small amount of this reacting with something else in the DNA can cause irreparable harm to a complicated system such as a living human being.

Simpler systems such as insects can withstand much more irradiation, while bacteria can withstand still greater levels of irradiation, but levels that will kill either do not greatly alter the taste and texture of meat.

Thus, low doses of irradiation can kill insects on fruit and grain or trichina in pork. Medium doses can keep meat fresh longer by killing much of the bacteria. High doses can sterilize meat.

The technology of an irradiator is quite simple in principle. The heart of an irradiator is a chamber that contains a radioactivity source. Food, medical disposables or other items get zapped as they slide through the chamber on a conveyer belt.

The source of the sterilizing rays is generally cobalt 60, a byproduct of the Canadian "CANDU" nuclear power plants. Cesium 137, a waste product from nuclear weapons production, is being promoted as an alternative, notably by Rep. Sid Morrison (R-Wash.), whose district harbors a major nuclear waste dumping ground, and by the Department of Energy, which is in charge of the waste. In addition, some are promoting the use of nonradioactive linear accelerators, but there are many technical problems in adapting these physicists' tools for studying the nature of matter to food preservation and disinfestation.

Despite its simplicity, it may be years, if ever, before food irradiation becomes widespread. First, the current regulations apply only to low doses suitable for insect disinfestation. Regarding regulations for doses that could extend shelf life or sterilize meat, FDA spokesman Jim Green said, "It's not going to happen this year or next year. We need more data to determine the safety of the process at higher levels."

Furthermore, in those countries where regulations provide no roadblock, irradiation has not exactly taken off. About 27 countries have approved food irradiation, some as long as 20 years ago. But only two countries, the Netherlands and South Africa, have commercial food irradiation, and these companies do only a few hundred thousand dollars business annually, according to Bahar Gidwani, an irradiation industry analyst with Kidder, Peabody & Co., Inc., of New York.

Nonetheless, Gidwani foresees a $1.3 billion food irradiation business in the United States by 1995, accompanied by fundamental changes in the way food is handled: "You would not necessarily have to have refrigerated warehouses and trucks, and people would not have to have as much refrigeration space in their homes."

But at present, other technologies may do most of the same jobs irradiation can do more cheaply and effectively. For example, Dave Meisinger of the National Pork Producers Council says that a method called ELISA (for Enzyme-Linked Immuno-Sorbed Assay) holds much more promise than irradiation for eliminating trichinosis from pork.

One reason is economics. ELISA (a method of testing each carcass for trichina) would cost a maximum of about 15 cents per hog, compared with 27-95 cents per hog for irradiation, according to a study commissioned by the nuclear weapons Byproducts Utilization Program of the Department of Energy. And the Byproducts Utilization Program study probably underestimated the cost of irradiation by a factor of three, because the cost it assumed for radioactive cesium was subsidized by the Department of Energy and was one-tenth market value.

Another is that irradiating crops is not as simple as it sounds and other technologies for preventing the spread of insect pests are more promising, says Dr. Milton Ouye, the Agricultural Research Service's national program leader for reducing postharvest losses. Like insects, picked fruit is alive and vulnerable to gamma rays. Every pest (including well over 100 subspecies of fruit fly) and every crop has a different level of tolerance. For each combination, research must be conducted to find a dose that is large enough to wipe out all pests on a commodity, but small enough to avoid blemishing the commodity. In many cases, it may be impossible to strike this balance, says Ouye.

Many alternatives to irradiation are potentially more effective and less expensive, says Ouye. These include worm detection devices, a variety of integrated pest management strategies, which use knowledge of pest' habits to foil them, and hot and cold dips for various fruits.

One irradiation entrepreneur recently lost a contract for disinfesting papayas to the double hot dip. "The guys I was working with said, 'gee, we really appreciate all the efforts you're gone through, but we're not going to do anything until we see how the double hot dip works' " says the entrepreneur, who insisted on anonymity. "The double hot dip is working like a charm."

Some in the food industry simply don't see the need for irradiation. "There is no reason to talk about multimillions of dollars for an irradiator which creates problems we don't have now," says Dr. Kenneth May of Holly Farms Poultry Industries, Inc. "Salmonella is destroyed by heating to 140 degrees for five minutes," he noted (though to prevent the raw poultry from contaminating other foods with salmonella, cutting boards and other utensils used to prepare it must be cleaned thoroughly).

Irradiation-sterilized meats might find specialized markets where cost would not be as crucial. Sterilization, which makes it possible to keep vacuum-packed meats for years at room temperature, requires first cooking the meat slightly to destroy natural enzymes that would otherwise digest it from within. It is then frozen prior to irradiation, to reduce changes in taste and texture. Ironically, the main criticisms of the irradiation process include changes in taste and texture, as well as loss of nutrients.

Several competing technologies are being developed, neither of which is as versatile as irradiation could be, but both of which are now in use, according to Cleve Denny, of the National Food Processors Association. Members of the Armed Forces have been eating thin slabs of meat and vegetables out of food pouches since 1979, says Bob Greene of the National Food Processors Association. The technology (food pouches) is similar to canning, but the products taste better because the process requires less heat.

Another process, called aseptic processing, has been used to treat milk and juice so that they can keep at room temperature for months. Denny says it might be used on ground meat in two to three years, but it is impractical for meat cuts.

Two industries that are unquestionably enthusiastic about irradiation are the spice and fish industries. "(Irradiation) cleans some spices better than chemicals. It cleans things more evenly," said a spokesman for the McCormick spice company. Irradiation firms in the United States are already sterilizing a small percentage of this country's spices.

Members of the fishing industry look upon irradiation as a way of bringing fresh fish to places like Omaha and St. Louis. "Seafood is probably one of the nation's most delicate foods," says Roy Martin, vice president for science and technology at the National Fisheries Institute. "If we can use irradiation to retard the bacteria that cause spoilage, we certainly would be able to deliver seafood further inland."

Irradiation has been widely touted as a technology that could reduce third-world hunger. Experts on third-world hunger disagree. "There's no shortage of food (in the third world) -- there are supermarkets in every city," says Medea Benjamin of the Institute for Food and Development Policy. "The problem is, people don't have money to buy that food."

Should food irradiation become widespread enough to revolutionize the industry, a shortage of irradiation source materials could stop it in its tracks. This, at least, is the impression one gets from talking to some proponents. "If food irradiation takes off, we've got a big problem," says Jacek (Jack) Sivinski, who directs irradiation research at CH2M Hill, a major environmental engineering consulting firm.

More than 135 irradiators operate worldwide, most of which sterilize medical disposables such as shot needles and surgical masks and gowns. The source material is almost always Canadian cobalt. Eleven reactors are now producing the cobalt, and Canada has fewer than 25 CANDUs. Moreover, nuclear power plants are not exactly selling like hotcakes.

Frank Fraser of Atomic Engergy of Canada, Limited (AECL), says he anticipates no difficulties in supplying cobalt. But Niel Nielson, president of Emergent Technologies and one of the bulls of food irradiation, is worried. "I see the market (for food irradiation) so big that I think AECL could not supply more than a few percent when they get every reactor they have producing cobalt," says Nielson.

U.S. reactors are unsuited to producing cobalt, says Todd Tillinghast of General Electric. "Once you start taking a couple of days additional shutdown because you have to change those targets sometimes, the (cost of) cobalt becomes $10 to $15/curie a measure of radioactivity ," says Tillinghast. Market value is about $1/curie.

Partly this and partly the desire to find beneficial uses for radioactive waste inspired the United States' push to use cesium 137 in irradiators. In 1984, the Department of Energy offered its stockpiles of cesium to irradiation firms at bargain-basement prices, and they were spoken for within several months and did little to alleviate the shortage at that time. No more cesium will be available until the end of this decade or the beginning of the next, and supplies will be a trickle compared to cobalt.

"I see a future where we're probably buying our cesium from those countries that are reprocessing (nuclear power plant wastes), like France, Germany, England, Japan," says Sivinski. But Jerry Brubaker, a consultant to the House Energy Committee's Subcommittee on Energy Conservation and Power, says that the revenue from separating cesium would not pay for the cost of removing it from the waste stream.

One alternative might be to irradiate food linear accelerators. But most members of the industry queried claimed that linaccs, as they are known in the trade, have low penetrating power, making them unsuitable for irradiating thick items such as boxes of oranges or carcasses. Nielson and others are working on an accelerator technology that he claims solves the problem, by converting particle beams into X-rays. But Sivinski cautions that "the (energy) conversion efficiency is very poor . . . it gets pretty pricey."

Irradiated food is not radioactive, because at the relevant doses radioactivity is not contagious among the elements present in food. The big concern is that the resulting chemical reactions in food might produce harmful substances. Studying the wholesomeness of irradiated food is a different task, because it is impossible to concentrate these substances in the diets of laboratory animals as has been done with additives like red dye No. 40. Instead, animals must eat truly massive quantities of irradiated food.

For example, in what was probably the most thorough animal study of irradiated food, mice, rats, beagles, hamsters and even fruit flies consumed a total of almost 300,000 pounds of sterilized chicken. The results appeared ambiguous. Coordinator Dr. Donald Thayer of the USDA summerized tens of thousands of pages thus: The studies "strongly support the safety of (irradiation), but there are some serious concerns which require careful consideration by qualified experts." Dr. Sidney Wolfe of the Health Research Group, a strong opponent of food irradiation, admits that irradiated food is probably not as dangerous as smoking, but says, "smoking is not an FDA-approved additive."

But the issue of health goes beyond harmful chemicals irradiated food might harbor to the way we handle food. Most people know better than to eat raw pork or hamburger. Almost everyone knows that if fresh fish looks and smells palatable, it is. Long before bacteria such as botulina make fish dangerous, spoilage bacteria render it disgusting.

Irradiation could change all that. Irradiation keeps meat fresh longer by decimating, but not destroying, the resident populations of bacteria. Some species of bacteria are more resistant than others. The danger of irradiation is that it could alter the bacterial balance of power, so that hazardous but odor-free species could multiply to dangerous levels before the spoilage bacteria could give off their warning stench. "Preliminary" research indicates the problem is not insurmountable, says Roy Martin of the National Fisheries Institute. Nonetheless, Clyde Takeguchi of FDA says the issue is of concern to his agency.

Still another health-related issue is public safety. Although irradiation is considered by proponents and antinuclear activists alike to be one of the most benign uses of radioactive materials, the worst radiological accident in North American history involved a medical irradiator. In 1983, the irradiator was sold to some Mexican physicians, but mysteriously ended up in a junkyard, according to Science magazine. The junkyard unknowingly sold scrap from the irradiator, including the radioactive cobalt source material, to a foundry, which incorporated it into reinforcing bar (rebar), used in building construction.

By sheer good fortune, a truck carrying rebar into the United States passed through Los Alamos National Laboratory, where it tripped a radiation alarm. The material was traced back to the foundry and to the junkyard. But by that time, a considerable amount of rebar had been sold into the United States, and all 50 states were forced to join the hunt for the material.

Several years from now, as you stalk the aisles of your favorite supermarket, an unfamiliar sight may greet you. On the label of the fish, perhaps, or above the bins with the mangos, you might see a little circle with a couple of flower petals on it next to the legend "picowave processed."

"It looks like a health food symbol -- it's a flower," groans an outraged Mark Robinowitz of the Health and Energy Institute. As for the word "picowave," says Robinowitz, "We've looked in dictionaries and have not been able to find it anywhere."

"Deliberate deception," says Sid Wolfe of the Health Research Group.

Proponents of food irradiation wanted the word "picowave" because they feared that the public would not buy the product if it were identified as irradiated. ". . . the public in general has an emotional, almost fearful response to food irradiation," Rep. Morrison once said. Morrison has repeatedly sponsored a bill that would make the promotion of food irradiation a national priority (it still has not passed). A consumer survey by Kidder & Peabody, Inc., found that only 16 percent of women would buy irradiated food -- knowing it would stay fresh longer -- versus 36 percent who would not, and 48 percent who "didn't know."