To solve the following problems: food is supercooled or frozen at -5°C or lower, and it is difficult to control the fool refrigerated for preservation, and it is difficult to restore the frozen food to its original state during thawing.

Food containing water, e.g., filled Tofu T, is supercooled or frozen with ultrasonic vibration while physically restraining it to prevent expansion. For example, a sealed container 9 filled with non-compressible fluid (alcohol A) or a granular aggregate P is used for restraining the food.