CONDUCTANCE MEASUREMENTS FOR DATA GENERATION IN PREDICTIVE MODELING

The electrical resistance of a growth medium inoculated with bacteria may be automatically recorded throughout an incubation period without the necessity for sampling. The rate of change in conductance is dependent on the bacteria studied, the medium composition and the prevailing growth conditions. The effect of growth medium composition, growth conditions and inoculum level on the conductance response was studied for Yersinia enterocolitica O:3. A large number of combinations of factors affecting the growth/activity of the bacteria could be studied simultaneously due to the large instrumental capacity of the Malthus 2000. A polynomial model based on conductance measurements was developed for Y. enterocolitica describing the effect of temperature, pH and L-lactate level on conductance response curve parameters. The model was used for predicting growth rates. Growth rates calculated from bacterial counts of Y. enterocolitica growing in minced pork corresponded to growth rates predicted using the polynomial conductance models.