A method of aseptically and adiabatically processing liquid or semi-liquid food product at ambient temperatures so that the food product is transported from one sterile environment (such as a food processing machine), and into another sterile environment (such as a food package) via a food package filling machine head. During operation of the filling machine head, plural surface portions alternate between exposure to ambient and exposure to the food product. The method includes steps such that microbes from the ambient are not allowed to migrate along these alternatingly exposed surfaces. The method includes steps of initially heat sterilizing the alternatingly exposed surfaces at elevated temperature and pressure using culinary steam. Subsequently, an ambient temperature sterilizing barrier is maintained at a selected location along each of the alternatingly exposed surfaces so that migration of microbes along these surfaces and to the food product is prevented. After the initial heat sterilization using culinary steam, substantially adiabatic conditions are achieved for filling packages with the food product. Apparatus for carrying out the method is also disclosed.