Modelling the effect of a heat shock and germinant concentration on spore germination of a wild strain of Bacillus cereus

The effect of different concentrations of l-alanine on the germination kinetics of a strain of Bacillus cereus isolated from liquid egg after heat shock during sporulation was studied. Germination at 30 °C and was followed by spectrophotometry. The higher the concentration of l-alanine within the range 100–1 mM the faster was the germination obtained. On the other hand, the application of a heat shock had an effect on the germination producing a diminution on the germination kinetic rates. The Weibull distribution function, a model that has been used for describing inactivation kinetics [Collado, J., Fernández, A., Cunha, L., Ocio, M.J., Martínez, 2003. Improved model based on the Weibull distribution to describe the combined effect of pH and temperature on the heat resistance of three strains of Bacillus cereus in carrot juice. Journal of Food Protection 66 (6), 978–984; Loss, C.R., Hotchkiss, S.H., 2004. Determination of thermal inactivation kinetics of microorganisms with continuous micro flow apparatus. Journal of Food Protection 67 (11) 2560–2564; Chen, H., Hoover, D.G., 2004. Use of Weibull model to describe and predict pressure inactivation of Lysteria monocytogenes Scott A in whole milk. Innovative Food Science and Emerging Technologies 5 (3) 269–276; Guerrero, S., Tognom, M., Alzamora, S.M., 2005. Response of Saccharomyces cerevisiae to the combined action of ultrasound and low weight chitosan. Food Control 16 (2) 131–139], was used for modelling germination experimental data. Results indicated that the Weibull distribution function model produced a good description of experimental data.