Sealed
for security
Rohit
Chawla explains the process of thermoprocessing, which has given rise
to retort packaging as an effective means to ensure quality of a product
over a longer period
The
industralisation of canned and bottled foods can be attributed to thermoprocessing,
due to the fact that the method is more suitable to meet food preservation
demands, both in economy and quality, than the other means available.
While other food preservation methods can only suppress or retard microbial
growth, thermoprocessing completely eliminates microbes from food and
this sterility can be preserved once the containers are tightly sealed.
These features of thermoprocessing procedures for food preservation
have been taken over by thermoprocess-resistant films emerging with
the progress of the petrochemical industry.
Such plastics combined with establishment of package manufacturing,
filling and sealing, and thermoprocessing procedures have given rise
to retortable packaging, which now plays a very important role in food
packaging.
Production systems of retort food
The retort food manufacturing system consists of
food preparing equipment, filling and sealing machines, retorting equipment,
sterilisation racks, sterilisation rack transfer equipment, cartoning
machines, and outer casing machines. The method adopted for filling
food varies according to the form and texture of food, namely, solid
food, mixture of solid and liquid food, or liquid foods. In any kind
of food packaging, it is crucial to ensure seal integrity. During the
process of filling and sealing, the pouches are de-aerated by physical
flattening of the pouch and outward tensioning from the two side seals.
In case of pouches containing solids, vacuum sealing machines are used
for vacuum packaging. The sealed pouches are placed on horizontal sterilisation
racks. The sterilisation racks are stacked on the tray stacker and conveyed
on the retort car rails into the retort for sterilisation.
It is necessary to use a superimposed airpressure- type retort in order
to prevent damage to pouches during heat sterilisation.
After sterilisation, the racks are unloaded onto the tray conveyer one
after another by a rack unloader and conveyed to the automatic dewatering
and drying machine. De-watered and dried products then undergo checks
by weight checker and a metal detector before they are packed in individual
cartons.
Packaging material and design
Certain parameters need to be kept in mind while
selecting the material and design for retort packaging:
Packaging material
The basic requirement for packaging materials used
in retort packaging is heat resistance.
Also, while selecting package composition and package shape, consideration
must be given to the nature of the food to be packaged, its required
shelf life and the package cost.
Package shapes can be roughly divided into pouches, standing pouches
and semi-rigid containers. These are available with various barrier
material compositions, such as aluminium foil, polyvinylidene chloride
or saponified ethylene – vinyle acetate copolymer. In case of large
pouches, four-layer composition is often adopted for higher drop strength.
Standing pouches using aluminium foil usually adopt the four-ply laminate
construction because of their inherently
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