The chief food sources of energy to the human body are fat, carbohydrate, and protein. Fats and carbohydrates contain carbon and hydrogen which can be oxidized to their end products, CO2 and H2O, both in the bomb calorimeter and in the body. In addition, protein contains nitrogen. This nitrogen together with some carbon and hydrogen leaves the body chiefly in the form of urea.
The energy yielding food factors are:
-Carbohydrates: banana, breadfruit, jackfruit, plantain, dates, prunes, raisin
-Proteins and amino acids: nuts, dried apricot, fig
-Fats: avocado, olive, nuts
The energy value of foods can be expressed in terms of kilo calories (KCal) or megajoules (MJ).
*Kilo Calorie: One kilo calorie is the quantity of heat required to to raise the temperature of 1kg of water through 10C. It is one thousand times the small calorie used in physics measurements.
*Mega Joule : One kilo calorie equals 4.186 kilo joules. Hence thousand kilo calorie equals 4.186×103kilo joules or 4.186 mega joules.
Most of the fundamental work on the energy value of foods was carried out by the pioneer scientists Rubner (in Germany) and his pupil Atwater (in USA) at the end of the nineteenth century. Rubner measured the heats of combustion of a number of different proteins, fats, and carbohydrates in a bomb calorimeter and also studied the heat of combustion of urine passed by a dog, a man, a boy, and a baby.
What is food energy value?
