Histamine Formation by Morganella Morganii Isolated from Trachurus Murphyii (chilean Mackerel)

Morganella morganii , the most histaminogenic bacteria in chilean mackerel, was isolated and used to study the effect of temperature on h istamine production in this fish. Growth and histamine production rates at different initial pH (4.0, 5.5, 6.0, 7.0) and temperatures (10, 15, 20, 30 °C) were studied in batch cultures of M. morganii in a synthetic medium (TSBH2% histidine). An Arrheniustype relationship between growth rate and temperature was found; its activation energy was 88.49 kJ mol. Bacterial growth and histamine formation were negligible below pH 5.0. The Leudeking-Piret expression for product formation rate was used; the α parameter was not significantly different at 30, 20 and 15 °C and its average value was 0.1 [mg histamine (mg cell)]. Assuming an initial protein content of 188 g (kg fish), a level of 500 mg histamine (kg fish) would be produced after 43 h at 15 °C or after 24 h at 20 °C. The prediction of histamine level at different temperatures can be used as a strategy of catch management. KeywordsTrachurus murphyii, Morganella morganii, histamine production.