Chapter 27: Scombrotoxin (Histamine) Formation
Scombroid poisonings have primarily been associated with the consumption of tuna, mahi mahi, and bluefish. However, Table #3-1 lists a number of species that are also capable of developing elevated levels of histamine when temperature abused (FDA, 2001a).
Histamine-forming bacteria are capable of growing and producing histamine over a wide temperature range. Growth is more rapid, however, at high-abuse temperatures (e.g. 70°F [21.1°C] ) than at moderate-abuse temperatures (e.g. 45°F [ 7.2°C] ). Growth is particularly rapid at temperatures near 90°F (32.2°C). Histamine is more commonly the result of high temperature spoilage than of long term, relatively low temperature spoilage. Nonetheless, there are a number of opportunities for histamine to form under more moderate abuse temperature conditions.
Once the enzyme histidine decarboxylase has been formed, it can continue to produce histamine in the fish even if the bacteria are not active. The enzyme can be active at or near refrigeration temperatures. The enzyme is likely to remain stable while in the frozen state and may be reactivated very rapidly after thawing.
Freezing may inactivate the enzyme-forming bacteria. Both the enzyme and the bacteria can be inactivated by cooking. However, once histamine is formed, it cannot be eliminated by heat (including retorting) or freezing. After cooking, recontamination of the fish with the enzyme-forming bacteria is necessary for additional histamine to form. For these reasons, histamine development is more likely in raw, unfrozen fish.
The kinds of bacteria that are associated with histamine development are commonly present in the salt water environment. They naturally exist on the gills and in the gut of live, salt water fish, with no harm to the fish. Upon death, the defense mechanisms of the fish no longer inhibit bacterial growth, and histamine-forming bacteria start to grow and produce histamine. Evisceration and removal of the gills in a sanitary manner may reduce, but not eliminate, the number of histamine-forming bacteria. However, when done under insanitary conditions, these steps may accelerate the process of histamine development in the edible portions of the fish by spreading the bacteria to the flesh of the fish.
With some harvesting practices, such as long lining, death can occur before the fish is removed from the water. Under the worst conditions histamine formation can already be underway before the fish is landed on the vessel. This condition can be aggravated when the fish is allowed to remain on the line for a period of time after death, a situation that in certain tuna species may cause its internal temperature to increase to a more favorable growth range for the enzyme-forming bacteria.
The potential for histamine formation is increased when the flesh of the fish is directly exposed to the enzyme-forming bacteria. This occurs when the fish are processed (e.g. butchering or filleting).
At least some of the histamine-forming bacteria are halotolerant (salt-tolerant) or halophilic (salt-loving). This causes some salted and smoked fish products produced from scombrotoxin-forming species to continue to be suspect for histamine development. Further, a number of the histamine-forming bacteria are facultative anaerobes that can grow in reduced oxygen environments (FDA, 2001a).
This will prevent the rapid formation of the enzyme histidine decarboxylase. Once this enzyme is formed, control of the hazard is unlikely.
Further chilling towards the freezing point is also desirable to safe-guard against longer-term, low-temperature development of histamine. Additionally, the shelf-life of the fish is significantly compromised when product temperature is not rapidly dropped to near freezing.
The time required to lower the internal temperature of fish after capture will be dependent upon a number of factors, including:
Once chilled, the fish should be maintained as close as possible to the freezing point (or held frozen) until it is consumed. Exposure to ambient temperature should be minimized. The allowable exposure time is dependent primarily upon the speed with which the fish were chilled on-board the harvest vessel and whether the fish has been previously frozen (e.g. on-board the harvest vessel).
Unfrozen scombrotoxin-forming fish has a safe shelf-life (days before elevated levels of histamine are formed) that is dependent upon the harvest methods, the on-board handling, and the time/temperature exposures throughout processing, transit, and storage. This safe shelf-life can be as little as 5 to 7 days for product stored at 40°F (4.4°C).
Any exposure time above 40°F (4.4°C) significantly reduces the expected safe shelf-life. For this reason, fish that have not been previously frozen should not be exposed to temperatures above 40°F (4.4C) for more than 4 hours, cumulatively, if any portion of that time is at temperatures above 70°F (21°C); or the fish should not be exposed to ambient temperatures above 40°F (4.4°C) for more than 8 hours, cumulatively, as long as no portion of that time is at temperatures above 70°F (21°C) after chilling on board the harvest vessel. The safety of these limits is dependent upon proper handling at sea.
Fish that have been previously frozen can safely withstand considerably more exposure to elevated temperatures during post-harvest handling. Such fish should not be exposed to temperatures above 40°F (4.4C) for more than 12 hours, cumulatively, if any portion of that time is at temperatures above 70°F (21°C); or the fish should not be exposed to ambient temperatures above 40°F (4.4°C) for more than 24 hours, cumulatively, as long as no portion of that time is at temperatures above 70°F (21°C), after chilling on board the harvest vessel. The safety of these limits is again dependent upon proper handling at sea.
Extended frozen storage (e.g. 24 weeks) or cooking minimizes the risk of additional histamine development by inactivating the enzyme-forming bacteria and, in the case of cooking, the enzyme itself. As previously mentioned, recontamination with enzyme-forming bacteria and significant temperature abuse is necessary for histamine formation under these conditions. Such recontamination may not be likely if the fish is processed under a conscientious sanitation program.
Sensory evaluation is generally used to screen fish for spoilage odors that develop when the fish is exposed to time/temperature abuse. It is an effective means of detecting fish that have been subjected to a variety of abusive conditions.
However, odors of decomposition that are typical of relatively low temperature spoilage may not be present if the fish has undergone high temperature spoilage. This condition makes sensory examination alone an ineffective control for scombrotoxin.
Chemical testing is an effective means of detecting the presence of histamine in fish flesh. However, the validity of such testing is dependent upon the design of the sampling plan. The amount of sampling required to accommodate such variability is necessarily quite large. For this reason, chemical testing alone will not normally provide adequate assurance that the hazard has been controlled. Because histamine is generally not uniformly distributed in a decomposed fish, a guidance level of 50 ppm has been set. If 50 ppm is found in one section, there is the possibility that other sections may exceed 500 ppm.
Observations for the presence of honeycombing in precooked tuna loins intended for canning is also a valuable means of screening for fish that have been exposed to the kinds of temperature abuse that can lead to histamine development. Any fish that demonstrate the trait should be destroyed (FDA, 2001a).
All lots received are accompanied by harvest vessel records that show:
1b. For receipt by primary (first) processor Histamine Testing Option):
Analysis of a representative sample of fish shows less than 50 ppm histamine in all fish in the sample;
2. For receipt by secondary processor (including warehouse):
3. For processing steps:
During processing and refrigerated (not frozen) storage that occurs before cooking (e.g. canned tuna "precook"): For fish that have not been previously frozen:
Commercial test products for histamine.
AOAC. 1995b. Histamine in seafood: Chemical method. Sec. 35.5.31, Method 957.07. In Official Methods of Analysis of AOAC International, 16th ed., P.A. Cunniff (Ed.), p.15-16. AOAC International, Gaithersburg, MD.
AOAC. 1995c. Histamine in seafood: Fluorometric method. Sec. 35.1.32, Method 977.13. In Official Methods of Analysis of AOAC International, 16th ed., P.A. Cunniff (Ed.), p. 6-17. AOAC International, Gaithersburg, MD.
Bateman, R.C., Eldrige, D.B., Wade, S., McCoy, Messer, J., Jester, E.L.E., and Mowdy, D.E. 1994. Copper chelation assay for histamine in tuna. J. Food Sci. 59(3):517-518, 543.
FDA. 2001a. Scombrotoxin (histamine) formation. Ch. 7. In Fish and Fishery Products Hazards and Controls Guidance. 3rd ed., p. 83-102. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Seafood, Washington, DC.
FDA. 2001b. Other Decomposition-Related Hazards. Ch. 8. In Fish and Fishery Products Hazards and Controls Guidance. 3rd ed., p. 103-104. Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Seafood, Washington, DC.
FDA. 1998c. FDA & EPA Guidance Levels. Appendix 5. In Fish and Fishery Products Hazards and Controls Guide. 2nd ed., p. 245-248. Department of Health and Human Services, Public Health Service, Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Seafood, Washington, DC.
Geiger, E. 1944. Histamine content of unprocessed and canned fish. A tentative method for quantitative determination of spoilage. Food Research 9(4):293-297.
Hungerford, J.M. and Arefyev, A.A. 1992. Flow-injection assay of enzyme inhibition using immobilized diamine oxidase. Anal. Chim. Acta 261(1-2):351-359.
Hungerford, J.M., Hollingworth, T.A., and Wekell, M.M. 2001. Automated kinetics-enhanced flow-injection method for histamine in regulatory laboratories: rapid screening and suitability requirements, Anal. Chim. Acta 438(1-2):123-129.
Hungerford, J.M., Walker, K.D., Wekell, M.M., LaRose, J.E., and Throm, H.R. 1990. Selective determination of histamine by flow injection analysis. Anal. Chem.62(18):1971-1976.
Lerke, P.A., Porcuna, M.N., and Chin, H.B. 1983. Screening test for histamine in fish. J. Food Sci. 48:155-157.
Lerke, P.A. and Bell, L.D. 1976. A rapid fluorometric method for the determination of histamine in canned tuna. J. Food Sci. 41:1282-1284.
Mopper, B. and Sciacchitano, C.J. 1993. Capllary zone electrophoretic determination of histamine in fish. JAOAC 77(4):881-883.
Ohashi, M., Nomura, F., Suzuki, M., Otsuka, M., Adachi, O., and Arakawa, N. 1994. Oxygen-sensor-based simple assay of histamine in fish using purified amine oxidase. J. Food Sci. 59(3):519-522.
Schutz, D.E., Chang, G.W., and Bjeldanes, L.F. 1976. Rapid thin layer chromatographic method for the determination of histamine in fish products. J. AOAC. 59(6):1224-1225.
Taylor, S.L., Lieber, E.R., and Leatherwood, M. 1978. A simplified method for histamine analysis of foods. J. Food Sci. 43:247-250.
Yen G. and Hsieh, C. 1991. Simultaneous analysis of biogenic amines in canned fish by HPLC. J. Food Sci. 56(1):158-160.
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