Retort pouch introduction
A retort pouch is a type of food packaging made from a laminate of flexible plastic and aluminum foils. Retort pouch is a type of food packaging made from laminated structure materials which can be heat treated. It has the advantages of both canned containers and resistant to boiling water plastic bags. It allows the sterile packaging of a wide variety of food and drink handled by aseptic processing, and it is replaced of traditional canning packaging. Mostly used for ready to eat products such as meat, sauce, fish, or some other liquid product. The pouch can be heated to 120-135 °C. Therefore, it is also called "soft can". Retort pouches are used in field rations, space food, camping food.
A retort pouch is able to withstand the thermal processing used for sterilization. The food is first prepared, either raw or cooked, and then sealed into the retort pouch. The pouch is then heated to 120-135 °C for several minutes under high pressure inside a retort or autoclave machine. The food inside is cooked in a similar way to pressure cooking. This process reliably kills all commonly occurring microorganisms (particularly Clostridium botulinum), preventing it from spoiling. The packaging process is very similar to canning, except that the package itself is flexible. The lamination structure does not allow permeation of gases from outside into the pouch. The retort pouch production varies from one application to another, as a liquid product needs different barrier properties than a dry product, and similarly an acidic product needs different chemical resistance than a basic product. Some different plastic layers used in retort pouches include:
polyester (PET) – provides a gloss and rigid layer, can be printed inside
nylon (bi-oriented polyamide) – provides puncture resistance
aluminum (Al) – provides a very thin but effective gas barrier
K-nylon or K-PET- PVDC coated materials provides a transparent but effective high barrier
Retort cast polypropylene (RCPP) – used as the sealing layer
This multi-layer structure prevents the retort pouch from being recycled into other retort pouches or food packaging. However, the material can be recycled into an aluminized resin or up-cycled into textile materials.The weight of a pouch is less than regular cans or bottles, and the energy required to produce each pouch is less than competing packaging from metals, paper, and glass.