Tuna is canned in edible vegetable oils, in brine, in water, or in various sauces. In the US, it is sometimes called tuna fish. In the United States, only albacore can legally be sold in canned form as “white meat tuna”; in other countries, yellowfin is also acceptable.The fish are then cleaned and filleted, canned, and sealed, with the dark lateral blood meat often separately canned for pet food. The sealed can itself is then heated (called retort cooking) for 2 to 4 hours. This process kills any bacteria but retains the histamine that can produce rancid flavors. The international standard sets the maximum histamine level at 200 milligrams per kilogram. An Australian study of 53 varieties of unflavored canned tuna found none to exceed the safe histamine level, although some had “off” flavors. The level of omega-3 oils found in canned tuna can be highly variable, since some common manufacturing methods destroy omega-3 oils.