User:Elisabetta Lambertini/Notebook/Salmonella/2010/10/21

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Salmonella decay in almonds

Modeling decay of Salmonella in almond kernels over time. Confirmed that no significant reduction is observed at -20C and 4C. Decay trend at room temperature (about 23C) are significant, and are best fit with an exponential function in the Log:

LogC=s*exp(-kT)+p

Eight decay experiment are available. Each decay curve was fitted with the following models (with LogMPN as y variable):

  • linear
  • 1-phase exponential
  • Baranji (using DMFit)

In general, the exponential function fit was best. Parameters across the 8 tests are similar. How to combine results into a function we can use for risk assessment? I fitted each parameter set (s and k) with statistical distributions (easier to work with in @Risk that resampling), and fits are reasonable, although they add a layer of arbitrarity.

Now including the new decay model in the risk assessment code.

Risk outcomes are relatively similar (less than one order of magnitude apart, with very low absolute values) between the risk assessment model using a linear decay and an exponential decay (in the Log).