The response surface curve fitted to the L. monocytogenes population, pH and aw for all storage temperatures over the storage period
for both cheeses showed an interaction effect between the independent variables of storage temperature and time on dependent
variables (L. monocytogenes population, pH and aw). Analysis of
variance showed that both the linear and quadratic models were
significant with P < 0.0001 for all parameters of both raw and pasteurised milk cheese. Overall, model predictions showed a good fit
with low RMSE values and high regression coefficients.
The models developed facilitated the comparative growth
behaviour of L. monocytogenes on raw and pasteurised milk cheese
stored at various temperatures for a 28 day period. Such types of
model will facilitate prediction of Listeria monoctytogenes growth
during shelf-life and will help to demonstrate compliance with
food safety criteria (EC 2073/2005). These models also highlight
that improper chill storage conditions at the point of sale may
result in growth of L. monocytogenes in cheese, thereby increasing
risk to the consumer.