Q. Determine the moisture content in the given sample of fat?
After undertaking this activity, you will be able to:
• assess the moisture content in the given sample of oil/fat, and
• check the given sample for conformance to the standard for moisture content.
Principle
Moisture is determined by drying the weighed test material in an air oven. The loss in weight due to evaporation is accepted as the moisture content. However, it has been observed that materials in the air oven method shall also entail loss of volatile and thermo-sensitive constituents, as well as, moisture. Also in case of oils, it is seen that highly unsaturated oils such as fish oils or linseed oil may oxidize under the test condition and an increase in weight rather than a weight loss may be recorded. Lauric acids and other short chain fatty acids slowly volatilizes under the test condition as their chains are short. Spattering also produces errors as it leads to the loss of sample during drying.
Several methods such as Dean and Stark method, Karl Fisher method are available for estimating the moisture content of an oil. However, for our estimation in laboratories, using the basic infrastructure, we will be conducting the moisture content with the air oven method.
Procedure
Carry out the experiment following the procedure enumerated herewith:
1) Weigh accurately about 10 to 15 g of the sample in the moisture dish, previously dried in the oven and weighed.
2) Place the dish in the oven maintained at 105 ± 1°C for 1 hour.
3) Cool in the dessicator and weigh.
4) Repeat the process of drying, cooling and weighing at 30 minutes intervals until the difference between two consecutive weighings is less than one milligram.
5) Record the lowest weight.
6) Calculate the moisture content using the formula given herewith.