Microbial growth parameters obtained from the analysis of time to detection data using a novel rearrangement of the Baranyi–Roberts model

Aims To explore the predictions of a novel rearrangement of the Baranyi–Roberts model ( BRM ) with time to detection data obtained from optical density data of microbial growth. Methods and Results Growth of E scherichia coli and S almonella Typhimurium under mild conditions of temperature (25–37°C), salt (0·086, 0·51 and 1·03 mol l −1 ) and pH (6·85–4·5) was examined using optical density. Time to detection (TTD) data were fitted to a model based on a rearrangement of the BRM. Observations showed compatibility with standard viable count studies and produced highly accurate specific growth rates and lag phase durations. At high salt and low pH , however, there was a substantial dependency on the initial inoculum for the observation of visible growth. At 30 and 37°C, with 1·03 mol l −1 salt, and at pH <5·75, no visible growth was recorded for E . coli at initial inoculum levels below 10 7  CFU ml −1 . Conclusions The rearranged BRM can be used directly with TTD data obtained from optical density measurements. Significance and Impact of the Study A distinct advantage of the rearranged model is that it allows for a very simple interpretation of easily obtainable data using standard nonlinear regression. The rearranged model gives to TTD data the same modelling capability that the BRM gives to plate count data.