CORVALLIS - A three-year study of albacore by nearly a dozen researchers in the Sea Grant Program at Oregon State University may result in relaxed regulations for local fishermen and boost a growing industry without risking safety or quality for consumers.
Scientists have determined that albacore caught off the Oregon coast does not rapidly develop allergen-causing histamines like its tuna cousins do. By the time histamines build up - it takes at least two days at room temperature - the fish is so spoiled you wouldn't want to eat it anyway.
Albacore tuna belongs to the fast-swimming Scrombridae family, known for rapid development of histamine in the flesh after catch, said Haejung An, a researcher at the OSU Seafood Lab in Astoria.
Most species of tuna, mackerel, mahi mahi, swordfish, marlin and bluefish are susceptible to histamine formation. Histamine, a neurotransmitter allergen, can cause mild to severe symptoms that are usually relieved by antihistamines. But it has been known to trigger fatal heart attacks in individuals whose immune systems are compromised and are suffering from heart disease, An said.
The allergen concern is well known by the Food and Drug Administration, which has maintained stringent handling guidelines for fishermen.
But albacore caught off the Oregon coast has no history of causing allergic reactions, said Ken Hilderbrand, an OSU Extension Sea Grant seafood specialist since 1969. He helped spur a three-year Sea Grant-funded effort to investigate the histamine concern and prevent any potential occurrences that might damage a growing regional industry. Some Oregon fishermen who used to catch salmon have turned to albacore, a tuna usually in demand for its firm, pale flesh.
Most tuna are known to have extremely high levels of free histadine in their muscles, An said. Bacterial enzymes convert that histadine to allergy-triggering histamine rapidly - as fast as four to six hours after catch. Chilling slows the process.
An and graduate student Shin-Hee Kim searched for the source of the bacteria involved in the transformation of histadine to histamine.
"If the bacterial source was natural, we could prevent it. If it was from contamination, we could remove the source through better sanitation and handling," An said.
They discovered that the most common histamine-producing bacteria, morganella morganii, was normally present in a fish's gut. Other bacteria were found largely in the gills. That meant careful cleaning of the fish held potential for protecting the meat, a theory that appears to hold true.
"Eviscerated fish were more attractive after three weeks on ice, did not develop such a pungent odor, and did not accumulate histamine much," An said.
Hilderbrand and other Sea Grant researchers had previously worked with fishermen to develop the most rapid way to cool fish to maintain quality - and in those susceptible fish, to prevent histamine formation. But An thought that even the fastest measures would leave albacore loaded with histamines. Her initial tests were a big surprise.
"We couldn't find any!" she said.
They began intentionally leaving sample albacore at room temperature for longer periods. At two days, it finally began to show some histamine formation. But "even among four-day, spoiled fish, some were below the FDA histamine guidelines. It was totally against our predictions."
With Sea Grant support, An is continuing her research to discover why Oregon albacore is so resistant to histamine formation. She's also looking at how much freezer time is necessary to kill the bacteria. And Shin-Hee Kim, an OSU graduate student, is continuing to work in An's lab with between 4,000 and 5,000 bacterial isolates to determine their histamine-forming abilities.
Hilderbrand used An's work to help develop hazard prevention procedures to protect the Oregon fishing industry and its consumers. While his new histamine-prevention procedures are awaiting FDA review, he's fairly confident they will be accepted. Regulations for albacore caught in tropical waters, which has more of a histamine problem, were recently relaxed because tests showed it also was less of a concern than previously thought, he said.
There has been no way for consumers to tell if albacore has high levels of histamine in its flesh - it has no odor, taste or smell. The practical result of the combined Sea Grant effort means that fishermen and consumers of Oregon albacore have little cause for worry as long as they avoid spoiled fish.