Abstract: A sterilizer which has two transfer chains moving through sterilizing and cooling tanks; open-backed transfer containers with holes in their walls and locking members at both ends, which are supported between the chains; and inner vessels containing the materials being treated, which have holes in the walls thereof and locking means, which are engageable with the locking members, at both ends thereof, and which are adapted to be removably inserted into the containers. Projections extend inward from the circumferential edges of the holes in the walls of the containers and/or inner vessels, serving to support the materials and define liquid passages between the materials and the inner surfaces of the containers and/or inner vessels.