A method for sterilizing/pasteurizing a food material such as cereal, vegetables or fruit merely by treating same for a short period of time, without using a substance which is toxic to the human body, to thereby inhibit the growth of fungi and ensure a long shelf life. The method comprises bringing the food material into contact with superheated steam at 250-620°C and then adding a calcium oxide-containing powder thereto and mixing therewith. The calcium oxide-containing powder may be added and mixed at the same time that the food material is brought into contact with the superheated steam. The duration of contact with the superheated steam is preferably 20-0.5 sec. It is preferred that the calcium oxide-containing powder is a natural calcium oxide (calcined calcium) powder which is obtained by calcining shells, corals, nacreous layer, eggshells or animal, fish or bird bones at a high temperature.
