Heat resistance of Bacillus cereus emetic toxin, cereulide

The study describes the effects of heating temperature and exposure time on the thermal stability of cereulide under different conditions (pH, presence/absence of oil phase and cereulide concentration).

Cereulide heat inactivation was investigated at 100, 121 and 150 degrees C under different alkaline pH values (8.6-10.6) and in the presence of oil phase (0.6-1.4%). Three different cereulide concentrations (0.5, 5 and 6 microg ml(-1)) were used. Cereulide detection was performed with computer-aided semen analyzer and with HPLC-MS. Highly alkaline pH was needed to achieve inactivation. At lower cereulide concentrations less drastic conditions were needed. Removal of alkaline buffer after the heat treatment resulted in the recovery of toxic activity.

Heat stability of cereulide has been proved to be remarkable, even at highly alkaline pH values, at all temperatures tested. The loss of activity appeared to be reversible.

The study demonstrates the inability of any heat treatment used in the food industry to inactivate cereulide. Food safety has to rely on prevention and cold chain maintenance. Cleaning practices also need to be adapted as cereulide may remain in its active form upon sterilization of used material.