| 摘要 |
PROBLEM TO BE SOLVED: To prevent a progress of pressure decrease in a package body at least for a period in which a food inside the package is cooled down up to a temperature suitable for eating and drinking by a method wherein a valve provided at the package body is designed so as to deform in accordance with heating of the food up to an extent wherein the valve cannot be re-closed within an initial stage of cooling down the food. SOLUTION: For instance, a disposable check valve 5 approximately 1.5 cm in the diameter and 3 mm in the thickness is incorporated in a covering film 4. Then, the valve 5 and especially a membrane 6 are designed so as to deform by a high temperature during a period wherein a water vapor is accumulated. Thereby, the valve can be prevented from closing at least at once until a heated food is cooled down up to a temperature suitable for eating. Therefore, an excessive pressure inside the package body is completely decreased and the inside of the package body can be prevented from becoming vacuum. As a result, a greater part of the package body expanded by the excessive pressure is settled and returned to its original shape, and the food can be taken out safely. |
