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Just like a machine, the human body requires fuel for its work. Our body receives fuel in the form of food to collect the energy required to perform day-to-day activities. Our body derives energy from the food through complex biochemical reactions involving enzymes, and the reaction is referred to as the combustion of food. The energy in the food is measured in terms of calories.
The calorific value of fat as measured in a bomb calorimeter
The bomb calorimeter contains mainly two containers, one being the bomb which is a cylindrical stainless steel container, and the other is known as a calorimeter which is made from copper. The bomb is supplied with oxygen through a valve and contains two stainless steel electrodes which are connected to a 6-volt battery when the process of combustion starts.
One of the stainless steel electrodes is attached to a crucible. This crucible holds the fuel, which is fat or butter in this case. A magnesium wire connects the fuel (butter) to both electrodes, thereby completing the circuit.
The calorimeter is filled with a fixed amount of water and has a mechanical stiller to maintain the temperature of water evenly inside it. It also has a Backman’s thermometer to detect even a minute rise in temperature.
The calorimeter is separated from the bomb by an air compartment from the inside and a water jacket from the outside so that no transfer of heat takes place from the system to the surroundings.
The fuel or butter is kept on the crucible, and the system is closed. The initial temperature is noted, and the electrodes are attached to the battery, which causes fuel combustion. Combustion of the butter causes heat release. This heat is transferred to the water jacket surrounding the calorimeter, and again the maximum rise in temperature is noted.
According to the principle of the calorimeter, the heat liberated is equal to the heat absorbed.
Let the mass of butter be in X grams = 1g
W be the mass of water in calorimeter = 3000g
w be the mass of water equivalent in a gram of calorimeter = 500g
t1 be the initial temperature = 250C
t2 be the final rise in temperature of calorimeter = 27.390C
L is the gross calorific value of fuel in calories per gram, which is to be calculated
Therefore, the heat liberated by the burning of fuel = Heat absorbed by water and apparatus
X * L = ( W + w ) * ( t2 – t1)
1 * L = ( 3000 + 500) ( 27.39 – 25)
L = 8370 cal/g or 8.37 kcal/g
So, the gross calorific value of 1g of butter, which is fat, is 8370 cal/g or 8.37 kcal/g.
The gross calorific value of fats ranges from 8 kcal/g to a value of 9.45 kcal/g.
Calorific value of fats
The energy obtained by the combustion of food is measured in terms of combustion energy per gram and is called the calorific value. Therefore, it is the amount of heat produced in calories when one gram of substance or food is completely burned.
This calorific value is represented in kilocalories per gram or kilojoules per gram. 1 kilocalorie is equal to 4.18 kilojoules.
Foods are classified into fats, carbohydrates or proteins based on their energy values or their calorific values. Fats provide very high energy and therefore have high calorific values. So different foods have different calorific values, and all are required for an average person to maintain a balanced diet.
Fats, being the highest source of energy providers in food, is also stored in the body and is used from time to time when the body is in a deprived state of energy.
Therefore, for a balanced diet, a person must include foods that provide carbohydrates, fats, protein oils, and vitamins. On average, an adult person requires 8000 to 12000 kiloJoules of energy per day.
Calorific value is measured in terms of gross calorific value. The gross calorific value of fats is 9.45-kilocalories per gram. This gross calorific value is measured by a special apparatus known as a bomb calorimeter. This apparatus works mainly on the principle of energy conservation.
Conclusion
The calorific value of fat is determined with the help of a special apparatus called a bomb calorimeter. This apparatus uses the process of combustion to determine the value. Similarly, different calorific values of substances like proteins or carbohydrates can be determined through it. The sole purpose of determining the calorific values of food substances is to know how many calories a particular food item can hold. Fats like butter are high energy sources as they contain very high calorific values.
