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Resistance of albacore to histamine formation and distribution and prevalence of histamine-producing bacteria in albacore |
S. H. KIM1, T. P. Pitta2, C. I. Wei3, and H. An3. (1) OSU-Seafood Lab, Oregon State Univ., 2001 Marine Dr., Astoria, OR 97103, (2) Dept. of Biological Sciences, Auburn University, 317 Life science Bldg., Auburn, AL 36830, (3) Dept. of Nutrition and Food Science, Auburn University, 328 Spidle Hall, Auburn, AL 36849 Histamine is the main cause of scombroid poisoning. It is formed post-mortem in fish by proliferation of bacteria synthesizing histidine decarboxylase to convert histidine to histamine. Scombroid fish such as tuna and mackerel are frequently implicated in outbreaks of scombroid poisoning due to high levels of free histidine in the muscles. Thus, monitoring histamine is a critical task for tuna industry under the FDA's scrutiny. Distribution and proliferation of histamine formers were studied in albacore tuna to better understand the bacterial histamine formation. Bacteria were isolated by using group-specific selective media (VRBG, PI, and TCBS agars) from the gill, skin, and intestine of fresh albacore as well as muscles during storage at 25°C. Histamine production by the isolates was confirmed by the AOAC fluorometric method. Histamine formers were identified by the Vitek identification system. Bacterial growth and histamine formation in fish muscles were determined by FDA and AOAC methods, respectively. Histamine-producing bacteria constituted a minor portion of bacterial flora in albacore. Histamine formers (mostly weak formers <1,000 ppm) were detected in the gill and skin of fresh fish, but isolated only with the enrichment step. They were isolated from the muscles when APC reached >107 CFU/g during storage, and Hafnia alvei were most prevalent in stored fish. The most prolific histamine former, Morganella morganii, was rarely isolated even from spoiled albacore. Coincidently, histamine began to increase gradually in muscles after albacore appeared spoiled. Low population of initial histamine formers in fresh fish and the presence of weak histamine formers during storage resulted in low histamine accumulation in albacore. This result supports the common observation that albacore has rarely been involved in scombroid poisoning. The future regulation should target the presence and proliferation of prolific histamine formers as the main contributors of histamine in fish.
Session 42, Seafood Technology: Safety, Processing
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