Abstract: A pressure vessel arranged for use as a steam cooker and employing multiple outlet connections is disclosed. One of the outlet connections is located in the vessel floor and is of such flow capacity as to freely pass collected food particles, water and steam from the vessel. Another outlet connection is located high on a vessel wall and is of such flow capacity as to release steam from the vessel at a limited rate. The outlet connections together with a steam inlet are opened and closed in a controlled sequence in order that the functions of defrosting, cooking and vessel purging be accomplished in an improved reliable manner.