Follows is a subject we should all be familiar with Dr. Fish: The Hazards of Histamine Here's how to prevent your fish from developing histamine By Roy E. Martin, Gofish.com News Publish date: November 02, 2000 08:40 AM A major emphasis in developing HACCP plans for scrombroid fish is controlling the formation of histamine. Twenty species are mentioned in the FDA’s "Fish and Fisheries Products Hazards and Controls Guide" (second edition) as capable of developing elevated levels of histamine when temperature-abused. Tuna, mahimahi and bluefish have primarily been associated with most of the histamine poisoning cases. A word of advice on the other 17 (mackerels, shads, herring-like fish and others): While these species are rarely implicated in histamine outbreaks, your HACCP plan should explain how you accommodate this potential hazard (occasional testing, area of catch and similar information). Scrombroid poisoning is one of the three most frequently reported illnesses associated with the consumption of seafood. Histamine is formed by the breakdown of histidine, which is found at fairly high levels in the muscles of fish belonging to the Scrombroidae family. Histamine formation is induced by high temperatures of fish after harvest. Accumulated concentrations of histamine are affected by the combination of time and temperature. Histamine is more commonly the result of high temperature spoilage than of long-term, relatively low temperature spoilage. Said another way, enzymes produced during microbial spoilage are responsible for the conversion of amino acids (histidine) to amines (histamine). Uninterrupted, the breakdown will also produce putrescine and cadaverine. Note: Putrescine and cadaverine may become the future indicators of seafood decomposition by FDA. Based on the best estimate of a threshold toxic dose for histamine, a regulatory action level of 50 ppm histamine per 100 grams of fish has been established by FDA. In most cases, histamine levels in illness-causing fish have been above 200 ppm, often above 500 ppm. From a search of the literature, holding scrombroid fish above 12 degrees centigrade generates histamine concentrations above 200 ppm. Rapid chilling of fish immediately after death is the most important element in any strategy for preventing the formation of scrombrotoxin (histamine). It is recommended that if fish have not been exposed to temperatures above 28 degrees centigrade, the fish should be placed in refrigerated seawater or brine at 10 degrees centigrade or less within nine hours of death, or placed in ice within 12 hours of death. For very large fish (above 20 pounds), the temperature should be reduced within six hours of death. These steps will prevent the rapid formation of the histidine enzyme. Once this enzyme is formed, control of the hazard of histamine is unlikely. Proper handling at sea means fish should not be exposed to temperatures above 40 degrees Fahrenheit (4.4 degrees centigrade), for more than four hours, cumulatively, after being chilled. If fish have been quickly frozen, they can safely withstand more exposure to elevated temperatures during post-harvest handling. Sensory and chemical testing are means of detecting histamine, as is the term "honeycombing" as applied to precooked tuna loins. Several quick screening test kits have been developed and are available commercially. Histamine poisoning can cause severe discomfort but mild in nature, rarely lasting for more than one day. It produces symptoms sometimes mistaken for those of allergic reactions (rashes, flushes, tingling and itching). If a customer reports such an incident, document the event very carefully; that may reduce liability.