Histamine formation by Morganella morganii isolated from Trachurus murphyii (Chilean mackerel)

Abstract

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 (TSBH- 2% histidine). An Arrhenius- type relationship between growth rate and temperature was found; its activation energy was 88.49 kJ mol-1. 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)-1]. Assuming an initial protein content of 188 g (kg fish)-1, a level of 500 mg histamine (kg fish)-1 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.