A container is provided with a valve opening at its bottom wall to permit steam to circulate into the container and to permit any condensation to drain from the container while the valve is open. The valve is closed by an expandable chamber in response to the pressure drop at the end of a sterilizing cycle. A valve controlling the flow of steam into the expandable chamber closes when subjected to the high temperature steam, thus capturing steam within the chamber. This steam expands when the pressure drops to close the valve in the container. The container lid and gasket permit steam to be withdrawn from the container but prevent air flow into the container. A vacuum created in the container at the end of the sterilizing cycle holds the container lid in place and holds the valve closed.