Tuna Fish

_x000D_ _x000D_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. While in the early 1980s, canned tuna in Australia was most likely Southern bluefin; as of 2003 it was usually yellowfin, skipjack, or tongol (labelled "Northern bluefin"). _x000D_ _x000D_As tunas are often caught far from where they are processed, poor interim conservation can lead to spoilage. Tuna is typically gutted by hand and later pre-cooked for prescribed times of perhaps 45 minutes to three hours. 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.