PURPOSE: To realize both good taste and long keeping quality by a method wherein food is sealed and thermally sterilized in a vessel made of heat-resistant plastic with fine ceramic powder mixed which radiates far infrared rays of a specific wave length.

CONSTITUTION: Since fine ceramic powder which is likely to radiate far infrared rays of wave length of 6 to 14 microns is mixed into a heat-resistant plastic vessel for installing food, when said vessel is thermally sterilized, far infrared rays of 6 to 14 microns, preferably 8 to 12 micron wave length, which has sterilizing capacity, resonance, water activating capacity, etc. are radiated to the food and penetrates into the inside. This sterilizes not only the outer but also the inside of the food, and causes the far infrared rays to resonate with the food and contained water to be activated so that the food can be matured in a short time and taste of the whole food can be uniformly good. In addition, even if heating temperature is lowered, or the heating period is shortened, sufficient sterilization is possible. If fine zeolite powder is used as the fine ceramic powder likely to radiate far infrared rays, the effect is further increased due to synergetic effect.