Packaging with pressure driven oxygen egress

A method of preserving food comprising:

• depositing dry ice and food within a packaging, the packaging comprising:
• (a) a flexible liner defining a wall aperture and an internal chamber, the internal chamber receiving the deposited dry ice and food, the internal chamber having an internal atmosphere;
• (b) a check valve mounted to the flexible liner and covering the wall aperture, the check valve configured to occupy:
• (i) a closed state blocking fluid communication between the internal chamber and ambient via the wall aperture and (ii) an open state enabling fluid flow from the internal chamber, through the wall aperture, and into ambient;
• closing the packaging by forming a seal across the flexible liner, wherein the dry ice sublimates within the closed packaging, pressurizes the liner, and causes the check valve to occupy the open state;
• allowing fluid within the internal chamber to vent through the open check valve until pressure within the liner stabilizes with ambient, thus causing the check valve to occupy the closed state.