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It can be softer than ice cream or as leathery as a pair of Bruno Maglis, and it tantalizes the taste buds like a set of wax lips. It is the unappetizing side effect of stress on meat.

So worrisome has it become in seafood-obsessed Japan that researchers at Hokkaido University are looking for ways to take the pressure off tuna to make the fish tastier and more visually appealing on supermarket shelves.

Tuna tends to thrash vigorously when caught, causing a rise in body temperature and a buildup of lactic acid in the muscles. Both hamper the ability of the fish to cool, leading to a whitening or "burning" of the flesh before slaughter, which cuts flavour and value.

So what exactly is the taste of stress? That depends on a confluence of factors, including the level and timing of stress and the type of animal, says Dr. Al Schaefer, a scientist at Agriculture and Agri-Food Canada's Lacombe Research Centre in Alberta.

"There is a taste of stress, but it's a complex situation," Dr. Schaefer said. "There is a particular stress pathway that depletes muscle sugars that are drivers for sweetness. The way ions are depleted, particularly sodium, potassium and magnesium, can drive salty and bitter tastes."

In a word, stress tastes bland.

"You would know the difference in texture; it leads to a toughening of the meat," said Dr. Tom Gill, director of the Canadian Institute of Fisheries Technology at Dalhousie University in Nova Scotia. "A rested harvest fish is juicier. It's more palatable."

Stressed-out meat has long been a concern of the cattle and pork industries in Canada, where food scientists say changes in the way livestock is reared and handled over the past three decades have reduced pressure on animals being led to slaughter.

Livestock researchers estimate the problem of stressed meat affects about 1 per cent of the 3.5 million head of cattle and 15 million hogs slaughtered each year in Canada.

But that tiny fraction adds up to millions of dollars in lost revenue in the $6.5-billion cattle and $3.4-billion pork industry.

The losses have forced the industries to constantly rethink the way livestock is bred and handled before slaughter.

Psychological stresses, including unstimulating holding pens and rapid corralling of animals into the abattoir, cause a rush of adrenalin and corticosteroids that harms muscle cells. Physical stresses, such as electric prods and flashes of hot and cold air, worsen the situation.

If the rush of stress hits minutes before slaughter, the meat can be damaged.

High stress levels in pigs can decrease the ability for muscle to retain water, turning pork products into the sweating, pale cuts of soft meat bound for the supermarket bargain bin.

While the cuts are edible, they can have the texture of a rubber chicken when cooked.

In cattle, the result is what is known in the industry as a "dark cutter."

"On a dark cutter, the meat will be mushy and taste like liver, which is not how I want my beef to taste," said Dr. Temple Grandin, an expert in livestock handling at Colorado State University whose research has led to changes in handling techniques. "That meat has to be downgraded. If it's real bad, it gets made into burger."

Dr. Grandin said companies such as McDonald's Corp. and Wendy's International Inc. have put pressure on commercial herders to alter their practices by auditing things such as the frequency with which they use electric prods and of slips and falls during herding.

Larry Martin, a senior fellow at the George Morris Centre, a non-profit agri-food think tank in Guelph, Ont., said industry concerns about stressed meat are at nowhere near the level they were 30 years ago, largely because of more humane handling practices.

He chuckled at the notion of reducing stress in tuna, recalling his fight with a 200-pound tuna off the coast of Costa Rica last year.

"I fought it for an hour and a half and it died before we got it in," Mr. Martin said. "It had to have been stressed, and it tasted wonderful. Am I going back this year? You bet."