Production and diffusion of histamine in the muscle of scombroid fishes

The fresh muscles of scombroid fish, big-eye tuna Thunnus obesus was incubated at 25°C after infection with two histamine forming bacteria, Morganella morganii and Photobαctrium phosphoreum. Both bacterium were detected not only surface, but also in the connective tissue slit of fish meat.Histamine was analyzed by paper electrophoresis separation and coloring with Pauly reagent. In case of M. morgαnii, histamine was mainly drastically accumulated at the level 3000 - 5000 ppm near infection point, until 32-36 hr. But in case of P. phosphoreum, histamine was detected at the level 1000 - 2000 ppm, until 36 - 48 hr, not only infected area, but also horizontally and vertically remote area. Among four tuna fishes, T. obesus was most susceptible to histamine production by the infection with the both two histamine forming bacteria, M. morgαnii and P. phosphoreum. Together with the histamine production, a few unknown spots positive to Pauly reagent were observed in the extracts from the muscle of scombroid fishes.