Thermal Food Processing

Thermal Processing of Ready Meals 383
to killing bacterial pathogens, such as Salmonella on poultry, it is especially
effective at destroying the microorganisms present on fresh fruit, such as strawberries,
and thus markedly extending their shelf life. Its biggest advantage is
that it has so little effect on the food itself that it is very difficult to tell if the
food has been irradiated. It also has some technical limitations, in that it is not
suitable for foods that are high in fat, as it can lead to the generation of offflavors.
This restricts its use for sterilizing ready meals. The only commercial
foods that are currently licensed for irradiation in the U.K. are dried herbs and
spices, which are notoriously difficult to decontaminate by other techniques,
without markedly reducing flavor. A major application for irradiation is in
decontaminating packaging.
12.5 CONCLUSIONS
Changing lifestyles has ensured that consumer preference continues to be on the
increase for ready meals as convenience foods. It is likely that thermal processing
of ready meals will remain one of the key methods for their manufacture. Many
thermal processing methods can be used for their production; however, two routes
forward are gaining in popularity:
1. In-pack pasteurization in combination with chilled storage. This is
being achieved through optimization of existing retort-based equipment
and thermal processing regimes, which can be used to produce ready
meals of high quality. Recent developments in overpressure retorts and
packaging formats have allowed this ready-meal sector to advance at
a rapid rate. Retorting has the advantage of pasteurizing both ready
meal and packaging together, which can extend the shelf life under
chilled storage.
2. Low-care and high-care factories (also known as low risk–high risk).
Ready meals of the highest quality are being manufactured using mild
or minimal heat processes for the components. The thermal processing
steps take place in the low-care parts of a factory and are followed by
packaging in high-care environments. Strict control of hygiene in the
high-care areas is essential in order that microorganisms are not introduced
to the food. Once packaged, there is no further preservation
hurdle apart from chilled storage.
Neither of the above methods can be classified as traditional thermal processes.
However, there is still a need to ensure that the thermal processing steps
are applied correctly, which requires that the same methodology for establishing
canning processes is followed. Both are pasteurization processes that require
chilled storage. This is because the consumer trends are for higher-quality ready
meals that can only be manufactured with mild thermal treatments and the
additional preservation hurdle of chilled storage.