An instrument for measuring the amount of oxidisable energy in a substance, by burning it in oxygen and measuring the heat produced.
An instrument used to measure the amount of heat produced by a weighted sample of food, and thus the food’s energy value.
An instrument for measuring the amount of heat produced by a food when oxidized.
The bomb calorimeter is an instrument used to measure heat production when a known amount of food is completely oxidized. It is a highly insulated box-like container. All the heat produced during the oxidation of a dried sample of food is absorbed by a weighed amount of water surrounding the combustion chamber. A thermometer registers the change in the chamber temperature. The instrument’s name is derived from the design of the combustion chamber, which is a small bomb. The energy value of protein foods obtained in this manner is higher than the actual biologic value because in biologic systems, the end products of oxidation must be excreted as urea, a process that costs energy. For instance, in a bomb calorimeter, the combustion or oxidation of protein yields 5.6 calories (23.5 kJ)/g; the energy yield from the oxidation of protein after correction for urea formation and digestive loss by the body is about 4 calories (16.8 kJ)/g. Corrections for digestive losses are also applied to the values obtained for the combustion of lipids and carbohydrates. The value of 4.1 calories (17.22 kJ)/g is rounded off to 4 (16.8 kJ) for carbohydrates and the value of 9.4 (39.5 kJ) for lipids is rounded off to 9 (37.8 kJ).
Any apparatus used to measure the heat lost or gained during various chemical and physical changes. For example, calorimeters may be used to determine the total energy values of different foods in terms of calories.
An apparatus for determining potential food energy. Heat produced in combustion is measured by the amount of heat absorbed by a known quantity of water in which the calorimeter is immersed.