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Abstract
A rapid and sensitive method has been developed for determination and quantification of cereulide in cream, rice and pasta. Samples are homogenised after addition of amylase to cooked rice and pasta, and cereulide is extracted with methanol. After the removal of water with methyl-tert butyl ether/hexane and evaporation until dryness, no further purification was required before analysis with liquid chromatography–tandem mass spectrometry (LC-MS/MS). Recently, both cereulide and 13C6-cereulide has become commercially available at high purities; hence, this method offers a more reliable quantification of positive samples than previous methods using valinomycin or in-house produced and purified cereulide as calibration standard. The introduction of amylase in the sample preparation improves both the extraction yield of cereulide from positive samples of starch-rich matrices such as pasta and rice, and the within-laboratory reproducibility of the analytical method. The LoQ of the method is 1.1 ng/g cereulide with RSDs ranging from 2.6% to 10%. The method is fully validated based on Commission Decision 2002/657/EC, suitable for routine analysis, and has been used to analyse samples from a cereulide food poisoning outbreak in a kindergarten in Norway. Cereulide production in different rice and pasta samples was investigated, showing that cereulide was unexpectedly produced by emetic Bacillus cereus in all eight pasta and rice samples.
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Acknowledgements
We would like to thank Tina O’Sullivan, Toril Lindbäck, Marte Monshaugen, Shani Wilhelmina Aarek Kidd and Olga Osinska for all help with the production of cereulide and microbiological analysis and Marianne Løken and Kristin Einarsen for the help with the chemical analysis of cereulide. We also thank Tjakko Abee for providing us with synthetic cereulide.