Load preheating and sterilizing method

An apparatus and method for preheating a load of goods sealed in a semi-permeable package and subsequently sterilizing the goods in a microbiocidal gas cycle wherein the heat is obtained from the condensate of low pressure steam, which is used to heat the goods. The system operates at or about atmospheric pressure with steam mixed with air to obtain the partial pressure of steam equivalent to the desired temperature, the air being present in the preheating step to prevent the package from rupturing due to the creation of an overpressure therein. The air is heated slightly above the desired load temperature. The air may be heated by absorbing the superheat from the steam as the line pressure is reduced.