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Development of a Growth Rate Model for Bacillus cereus sensu lato in Dairy Products

posted on 2023-05-25, 05:08 authored by Thomas RossThomas Ross, Bartlett, Z

Dairy Food Safety Victoria requested the Centre for Food Safety and Innovation (CFSI) to develop a new predictive microbiology model that could be used to predict the potential growth of Bacillus cereus in Australian dairy products during cooling after thermal processes or in storage and distribution.

CFSI undertook a search of the ComBase database of microbial growth rates and collated 68 growth rate data for records of B. cereus growth in milk products, but also collated 389 data for growth in analogous laboratory broths. The data for growth rates in milk were limited to temperatures less than or equal to 30°C, and so were not adequate for prediction of B. cereus growth upon cooling after thermal processing, because the upper temperature limit for growth of B. cereus is in the range 40 – 58°C.

From analysis of the available data it was shown that growth rates in laboratory broths were not systematically different from growth rates in milk-based media. This enabled more data, covering a much wider temperature range (i.e., up to 50°C), to be used for the model development.

Additionally, research undertaken by Zoe Bartlett as part of her B.Sc. Hons studies, contributed another 875 data for growth rates of strains of B. cereus isolated from Australian dairy environments and dairy products, over a temperature range of 5 – 45°C, in the modelling.

A predictive model was developed to estimate the growth rates of B. cereus sensu lato in the range 4 – 58°C. The model can also predict growth rates at different levels of confidence, e.g., that 95% of observed results will be below the rate of growth predicted by the model. The level of confidence can be chosen by the user.

Further development of the model to include the effects of growth restrictive pH or water activity on expected B. cereus growth rates is discussed.

The model will be incorporated into software for use by Dairy Food Safety Victoria.


Dairy Food Safety Victoria


Commissioning body

Centre for Food Safety & Innovation, Tasmanian Institute of Agriculture




Tasmanian Institute of Agriculture (TIA)


Centre for Food Safety & Innovation, Tasmanian Institute of Agriculture

Place of publication

Hobart, Tasmania

Repository Status

  • Restricted

Socio-economic Objectives

Dairy products not elsewhere classified

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