International trade in refrigerated cargo continues to increase, providing growth opportunities for a wide variety of carriers.

Airlines, containership companies and operators of breakbulk and "pallet- friendly" reefer ships all say the refrigerated cargo business is booming.These various methods of carrying refrigerated cargo have their distinct advantages and disadvantages. But, as volumes grow and technology improves, competition among them is heating up.

Air transportation, of course, is much more expensive than moving cargo by water. But, for certain premium products, shippers are willing to incur the additional cost.

Salmon roe, sea urchins, fresh tuna and salmon, fine cheese, cherries and strawberries - gourmands always have been willing to pay extra for fine, fresh products flown from around the world.

But advances in reefer containers are allowing some products that formerly only traveled by air to move by ship.

Chilled, as opposed to frozen, beef moving to Japan is "a big new market," said Tom McGoldrick, a vice president at Mitsui O.S.K. Line. He estimated that several hundred containers of chilled beef are moving to Japan each month.

At one time, chilled beef moved strictly by air. Greg Smith, today a vice president of Colography Group, a consulting company, and a former cargo executive at Qantas Airlines, recalls how, in the mid-1980s, Qantas set up an elaborate system for moving chilled beef from Australia to Japan.

Japanese inspectors were present at the slaughterhouse in Queensland to watch the butchering. Meat was chilled to a bone temperature of 38 degrees, packed in special insulated disposable containers that, because of the presence of the Japanese inspectors in Australia, did not have to be inspected by customs and were never opened until they actually arrived at the supermarket in Japan.

Japan later "liberalized" meat imports by eliminating quotas - but, at the same time, increased its tariff to 70 percent. The levy will be reduced to 60 percent this April.

The high tariff and the elimination of quotas has created new opportunities for container carriers like American President Lines Ltd. and Mitsui.

"The conversion has been very successful," said Patrick Brecht, director of special commodities, technical services at APL.

He said it costs about 25 cents to move a pound of chilled beef on the carcass to Japan by sea compared to $1.25 a pound by air. With the high tariff, the lower cost of water transportation has become critical.

New Technology Is Key

Mr. Brecht notes that there have been substantial advances in refrigerated container technology.

Temperatures can be held within a narrow range and atmospheric gases also can be controlled so carbon dioxide levels can be increased and oxygen levels decreased.

This helps retard spoilage and improves the texture of products such as asparagus, said Mr. Brecht.

These high-tech containers aren't cheap. APL has a fleet of about 5,500 reefer boxes. A 40-foot box with refrigeration costs about $26,000 to $30,000, and carriers also must spend $10,000 for a generator and $7,000 for a chassis. APL gets about 35,000 reefer loads with its fleet in a year.

A former professor at Cornell University and an expert in what he calls ''post-harvest and slaughter biotechnology," Mr. Brecht said it's important for carriers and shippers to understand the expectations of their customers and to have a thorough understanding of the entire process of moving meat from the range to the customer's plate.

He said APL's success in moving products like chilled beef to Japan has as much to do with the partnership arrangements APL has worked out with truck operators, railroads and meat companies as it does the new high-technology reefer boxes.

The company is expanding the markets to which it moves chilled products - it is beginning shipments of chilled beef to Taiwan and South Korea and is adding products such as asparagus and chilled pork.

The increase in chilled product is not restricted to U.S. exports. APL is moving mangoes from the Philippines to Japan. Mr. Brecht expects increased quantities of leafy vegetables, flowers and even strawberries to move by sea container as technology advances.

Reefer Ships Still King

While the container carriers are hauling more refrigerated cargo today than ever before, the amount of cargo they haul is dwarfed by that carried by operators of breakbulk and "pallet-friendly" reefer ships.

About 186 reefer ships are expected to be added between 1989 and 1993, about a 20 percent increase in the world fleet, according to the American Bureau of Shipping.

One of the largest operators of reefer ships in the world is Great White Fleet, the shipping arm of Chiquita Brands.

John Webber, director of fleet operations, said operators of reefer ships are increasingly competing with container carriers by including container slots on their vessels and soliciting that cargo.

A banana carrier like Great White Fleet is well positioned to compete with a traditional container carrier, he said, because its underlying banana business allows it to make more frequent voyages and call at more ports than a traditional liner carrier.

Palle Mathiesen, general manager for J. Lauritzen (USA) Inc., one of the world's largest independent operators of reefer ships, said that over the last two or three years operators of traditional reefer ships have added a great deal of container capacity to their fleets.

Some of his company's ships are deployed on regular liner routes, but many of its vessels tramp on a worldwide basis, following harvests and slaughters on a seasonal basis - from the Chilean fruit trade to the Argentinian and South African trades to Australia and New Zealand.

While reefer ship operators sometimes compete head-to-head with container companies, "We are mostly a south-to-north business while they are circling the world around the equator. It's really a different trading pattern and philosophy," Mr. Mathiesen said.