The TTD calculation is dependent on
achieving the pre-set 11 mS change in three successive readings
and looking at the results from the plate counts it is clear that it was
too strict for the slower impedance change produced by the strain
in the repeat experiment. If there was an adjustment change in the
detection criteria from 11 mS to 9 mS, which is still significantly
above background, it would produce a TTD of 9 h and 37 min and a
detection level of 8.5 log CFU/g. The need for this potential
adjustment is not surprising given the flat nature of the conductance
changes for the strain and also highlights the necessity of
tailoring the detection criteria for some strains and matrices.