Gross calorific value is a the calorific value of a substance that is obtained by combusting the substance completely. This term is also known as the heat of combustion of a compound.
The heat of combustion of a compound is the energy that is released as heat when a compound undergoes combustion using oxygen. The released energy can be measured in calories to determine the calorific gross value for food compounds. To determine this value for food compounds the food sample is placed into a bomb calorimeter and combusted. The amount of heat released by the combustion is measured and converted into calories.