| 摘要 |
"RETORTABLE PACKAGES" A retortable, hydraulically solid, sealed package (10) containing a liquid or semi-liquid food product (24) comprises a thermoplastics container (12) formed by a thermo-forming process and a heat-shrinkable thermoplastics closure diaphragm (20). The closure diaphragm is heat-sealed to a rim (18) of the container after the headspace above the product has been evacuated, and is subsequently subjected to external pressure so as to be non-elastically stretched and made to lie wholly in contact with the enclosed product. When retorted (e.g. for sterilisation) the package suffers no visible deformation of the container (12), despite the considerable volume shrinkage of the container which may occur. The loss of volume caused by this volume shrinkage is accommodated by a reduction in the concavity of the diaphragm (20) caused by a corresponding heat-induced shrinkage of the diaphragm material. The diaphragm continues to exhibit a pleasing, smooth or smoothly curving surface, and the retorted package has a consumer-acceptable appearance.
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