Prediction of overpressure required for seal integrity during sterilization of semirigid food and drug packages

Heat processing semi-rigid packages with a steam/air mixture requires an overpressure to ensure seal integrity. A method was developed to calculate the overpressure needed to ensure seal integrity, during thermal processing, of semi-rigid packages that contain a liquid food or drug. An equation was derived relating total retort pressure (steam and air) required during sterilization to retort temperature, product water activity and tensile seal stress at the sterilization temperature. The proposed method was tested, under commercial sterilization conditions (123–127°C for 30min), with individual packages containing a dilute saline solution. The method was found useful for predicting the total retort pressure (steam and air overpressure) needed to ensure seal integrity and to prevent leakage of packages.