Journal of Food Safety vol:35 issue:2 pages:179-192
The time-to-detection (TTD) method is a rapid and high throughput approach for the estimation of microbial growth parameters (maximum specific growth rate μmax and lag phase duration λ), which relies on optical density (OD) measurements. The performance of this method depends on several factors that are often selected in an arbitrary way. In this work, a sensitivity analysis was performed to assess the effect of several key factors on the resulting output data of this method with Listeria monocytogenes. The factors showing higher influence on the results include (1) the calibration curve relating viable plate counts and OD data; (2) the approach to estimate TTD values; (3) the detection limit of OD measurements; and (4) the range of the initial cell concentrations considered (Ni). In general, lag phase (λ) estimates were more sensitive than maximum specific growth rate (μmax) estimates. The approach to estimate TTD values and the OD detection limit was the most influential factors for the μmax and λ estimation. This work has illustrated that, despite all the advantages of the TTD method, there are crucial steps in experimental design and data processing that significantly influence its output in terms of lag phase duration and maximum specific growth rate.