The invention proposes a method of determining core temperature of food in a closed container, the method comprising the steps of: adjusting heating power supplied to the container to allow internal temperature of the container to change within a predetermined duration; obtaining information related to the change of internal temperature of the container; and determining the core temperature of the food based on the information related to the change of internal temperature and predetermined relationships between information related to change of internal temperature of the container and core temperatures of the food. The invention also proposes an apparatus for determining core temperature of food and a food processing device.