Determination of Moisture Content of Food by Hot Air Oven Method
The aim of this experiment is to determine the Moisture Content of a solid food sample by Hot air oven method. The principle and the uses of Hot air oven and the complete procedure of moisture content determination of food are discussed below-
Water is an essential component of food samples. When heat is provided to the food sample, moisture evaporates, which leads to a decrease in the sample’s weight.
This decrease in sample weight can help us to calculate the difference in the weight between the original sample and the oven-dried sample, which is, in fact, the weight of water evaporated.
A Hot Air Oven is a closed thermally insulated chamber with a door. The chamber is a composition of layers that don’t allow heat exchange between internal and external surroundings. The temperature is set by knobs provided on the outer portion adjacent to the door.
Hot air Oven was initially developed by Louis Pasteur to sterilize equipment and materials using dry heat. The Sterilization may be Dry Heat Sterilization or Moist Heat Sterilization. In Dry Heat Sterilization, the equipment that is not intended to be made wet/moist, melt, catch fire or change form, when exposed to high temperature.
Moist Heat Sterilization uses water to boil items or steam them and does not take much time as compared to Dry Heat Sterilization. However, Hot air oven uses Dry Heat Sterilization.
PRINCIPLE OF HOT AIR OVEN-
Sterilization by Dry Heat is accomplished by Conduction. The heat is absorbed by the outer surface of the item to be sterilized and then passed layer by layer towards the center of the item. The entire item will eventually reach the temperature required for the sterilization to take place.
Dry Heat does most of the damage by oxidizing the molecules. the essential cell constituents are destroyed and the organism dies. The temperature is maintained for almost an hour to kill the most resistant of the spores. This is the hot air oven principle.
1. Take two moisture dishes (as one of them shown below) including one replicate for better accuracy.
2. Put them in the Hot air oven at 105°C for half an hour. After half an hour, put them in a desiccator for 5 minutes and record their weights immediately. Label the reading as W1 and W1(r) respectively. Here r is written for replicate. A commonly used desiccator is shown below-
3. Put your 5g sample in each of the moisture dishes and weigh them accordingly. Label their reading as W2 andW2(r).
4. Now put the dishes as in step-3 into Hot air oven for 5 hours at 105°C or at 130°C for 3 hours. Generally, former temperature and time combination is considered.
5. After 5 hours, take the moisture dishes out and put them in Desiccator immediately for 5 minutes to cool down, and take their weight accordingly. Then put them again in the oven at the same temperature for 30 minutes and take their readings afterward.
6. Choose the reading for the sample and replicate, whose value is less. Generally reading taken after 30 minutes in Step 5 is less than before. So, label that reading as W3 and W3(r).
Repeat the same calculation for the replicate. The replicate and the sample’s value of moisture content should be close to each other. The Formula for calculation is as follows-