Try waiting for the pressure cooker to cool the point that it's no longer pressurized without releasing any steam. In general, if you have a container of wet t

Try waiting for the pressure cooker to cool the point that it's no longer pressurized without releasing any steam. In general, if you have a container of wet things in a pressure cooker (e.g. a bean with its seed coat, but a jar with a lid works the same way), when the pressure outside the container drops below the pressure inside the container, the net force tries to expand the container. If the pressure inside the container drops below the vapor pressure of whatever is in the container (which is likely _above_ ambient pressure in a hot pressure cooker), the contents will boil, which can cause various unpleasant effects. This can be minimized by trying to keep everything inside roughly in equilibrium while the pressure drops below ambient. Or a pressurized cooling system could be used in which the pressure cooker is pressurized above the vapor pressure using something other than water vapor (e.g. air, but an inert gas could be used, too), and then the contents can be cooled as fast as desired without risk of boiling or rupturing anything. I've never heard of anything resembling the latter for home use. If I understand correctly, commercial canning operations will cool their jars under pressure while spraying the outside with disinfectant to minimize the risk of anything living getting in before the jars fully seal.