Thermal Death Times of Hafnia alveiCells in a Model Suspension and in Artificially Contaminated Hot-Smoked Kahawai (Arripis trutta)

Abstract

In New Zealand the product most frequently implicated in cases of scombroid poisoning is hot-smoked kahawai (Arripis trutta). Using a Hafnia alvei strain, previously isolated from a portion of hot-smoked kahawai with a histamine levql of 1,659.4 mg/kg, thermal death trials were carried out in a model suspension (0.1% peptone) at 54, 55, 56, 57, and 58°C. From the linear regression line (R2 = 0.98) fitted to observed D values plotted against temperature, calculated D values for 54, 55, 56, 57, and 58°C were estimated to be 0.63,0.36,0.20,0.11, and 0.06 min, respectively, giving a z value of 4.14°C. Thermal death trials were also carried out for H. alvei associated with hot-smoked kahawai at 54, 55, 55.5, 56, and 57°C. From the linear regression line (R2 = 0.93) fitted to the data, calculated D values for 54, 55, 56, and 57°C were estimated to be 1.42, 0.74, 0.38, and 0.20 min, respectively, giving a z value of 3.57°C. Results indicate that hot smoking has the potential to eliminate H. alvei from seafood products.