Foodstuffs such as cereals, vegetables or fruits can be sterilized and disinfected by simple short-time processing for preservation of them over an extended period of time without recourse to substances harmful to human bodies, and prevention of growth of mold.After a foodstuff is brought into contact with overheated steam having a temperature of 250° C. to 620° C., calcium oxide-containing powders are added to and mixed with it. The foodstuff may come into contact with overheated steam simultaneously with addition and mixing of the calcium oxide-containing powders.The time of contact of the foodstuff with overheated steam is preferably 20 seconds to 0.5 second.The calcium oxide-containing powders are preferably natural calcium oxide powders obtained by firing shells, coral, the nacreous layer, eggshells, or bones of animals, fishes or birds.
