An apparatus and method for processing food products is provided. The product conditioning system includes an inlet assembly, a pressurizeable tunnel and an outlet assembly. The inlet and outlet assembly pressure vessels include a pair of vertically extending parallel screws for transporting food products from one end of the pressure vessel to the other. The pressurizeable tunnel includes a heating stage having microwave sources for irradiating food products so as to pasteurize or sterilize prepackaged food. The pressurizeable tunnel further includes a heat maintenance stage and product cooling stage. Both the heat maintenance stage and product cooling stage include vertically extending pressure vessels. Within each pressure vessel, two pairs of parallel rotating screws are positioned for moving food products through a liquid environment at a desired temperature for continued pasteurization or sterilization in the heat maintenance stage, and product cooling within the cooling stage.
