How is the calorie content of food calculated?
A calorie is the amount of energy required to raise the temperature of 1 gram of water 1 degree Centigrade. The calorie measure used commonly to discuss the energy content of food is actually a kilocalorie or 1000 real calories. This is the amount of energy required to raise 1 kilogram of water (about 2.2 pounds) 1 degree Centigrade. The particular food being measured must be burned in a calorimeter, so that the heat released from the food can be accurately measured. This amount is used to ascertain the G.E.V. of the specified food. This number is then multiplied by, usually, 85%; which represents the loss happening during human digestion. Portion control will reduce the calories, though I doubt tapping a biscuit reduces it by much.