These are some of the simple tests for identifying a lipid(Fats/oil) or detecting it's presence in a solution. These assays can be carried out in a laboratory.
They include....
Grease Spot test: lipid cannot wet paper, so we use this property of oil to detect its presence..
Method; add a drop of oil sample on a piece of paper, if a greasy spot develops, then the presence of oil/lipid is confirmed.
Solubility Test: lipids are organic compounds and as such they dont dissolve in polar solvents like water, instead they float. The solubility of lipids is based on the carbon length of the constituent fatty acids. Of the sample dissolves in ether or chloroform, but floats in water, then a lipid is present.
Presence of free Fatty acid: fatty acids and glycerol are the basic building blocks of lipids(fats and oil). Identification of fatty acid in a sample will confirm the presence of lipids!
Method; add 2 drops of phenolphthalien solution into a test tube containing 2 drops of alkali, the resulting pink color will disappear after drops of the test sample is added to the mixture if fatty acid is present.
Saponification Test: hydrolysis of Esters into their component Alcohol and Salt occurs after the addition of an Alkali. Oils and Fats naturally have long chains of fatty acids, a type of acid capable of forming Soap.
Hence if the Salt that results from the Hydrolysis of the Ester is a Soap,
then the presence of Lipids is confirmed!
Emulsification: oil is not soluble in water, hence when both liquids are mixed and shaked, the former breaks into tiny droplets called emulsions. This droplets then floats on the surface of the water in the tube. After some time, they merge together and the emulsion is lost.
To make an emulsion permanent, an emulsifying agent like bile salt or soap is used.
Emulsification is very necessary for the digestion of lipids in the body.
Method for testing: Add 3drops of sample in a test tube containing a small amount of bile salt. Shake and observe..
If tiny droplets of oil are seen in the solvent, then the Lipid is confirmed!
Test for the degree of Unsaturation of fatty acid: unsaturated fatty acids have some double ir triple bonds in their carbon hydrogen lattice. This degree of unsaturation
Is determined in a laboratory using halogens, those multiple bonds are chemically active, hence they react. Bromine or iodine solutions can be used in this case.
Method: a set of 4 test tubes is set up in series
In the first, a drip of shark liver oil is added, in the second, one drip of coconut oil, third tube gets an equal amount of vegetable ghee(derived from vegetable oil through hydrogenation). The last tube contains water and serves as control reaction.
Drops of bromine water is is subsequently added to these tubes in a systematic manner, until a permanent yellow colour is formed.
At this point, the no. Of drops of bromine water added is estimated and used as a reference for the degree of unsaturation in the fatty acids in each tube.
Health Tip: Excercise is generally regarded as a healthy life style, because it prevents the accumulation of Fats, which may find their way into the blood stream where they block the blood vessels to cause stroke High blood pressure, Kidney failure and other diseases....
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