A retort pouch is constructed from a flexible metal-plastic laminate which is able to withstand thermal processing used for sterilization. The food is first prepared, even raw or cooked, and then sealed into the retort pouch. The pouch is then heated to 240-250°F (116-121°C) for several minutes under high pressure, inside retort or autoclave machines. The food inside is cooked, similar 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 doesn't allow permeation of gases from outside into the pouch. The retort pouch construction varies from application to application, as a liquid product needs different barrier properties than a dry product, similarly an