has to be noted that both type 3 products that obtained a P70 2
were products with a simple structure (cannelloni and schnitzel).
All other type 3 products were mixed-structure meals (e.g. pasta
and sauce). Not only did more type 1 products obtain the set Pvalue,
but also the obtained P-values were substantially higher for
type 1 products than those for type 2 or 3 products. Four out of five
type 1 products that received an adequate heat treatment, received
a treatment higher than P90 ¼ 1, while this was not the case in the
other product-types. It is surprising that in particular type 1
products achieve a P70 of 2 min during reheating. These products
have had the most severe heat treatment during processing and are
not prone to recontamination and thus do not need to be reheated
to eliminate L. monocytogenes. However, they are more likely to
reach adequate temperatures and P-values during reheating. This
difference can be partially due to the packaging techniques used.
The type 1 products that obtained high P-values were packed in
plastic bags while type 2 and 3 products were mostly packed in
trays. During reheating the bags retained more steam than the
trays, which in turn increased the temperature in the bag. This
illustrates the importance of packaging in the reheating step.