Our objective is to study some simple tests of oils and fats.
Fats and oils are concerted source of energy. Certain percentage of body weight of human being is fat and 20-35% of calories should come from fat. Fats in the diet are essential for good health and are needed for the growth of the body and the processing of vitamins. They make up part of all cells and help to maintain the body temperature. They form fatty tissue around delicate organs to protect them from injury.
Chemically fats and oils are triesters of glycerol and higher fatty acids. They are of animal or plant origin. Desi ghee is animal ghee while vanaspati ghee is vegetable ghee. Fats are solids while oils are liquids at ordinary temperature. Fats and oils may be saturated or unsaturated.
Saturated fats contain only single bonds within the carbon chain. Saturated fats are of animal origin and are usually present in solid form. It increases the blood cholesterol level. Some examples are meat fat, butter etc. Coconut oil and palm oil also contain saturated fat.
Unsaturated fats contain double bonds within the carbon chain. Unsaturated fat is found in fish like salmon and tuna, nuts, seeds etc.
Oils and fats are soluble in organic solvents like, chloroform, alcohol etc. but are insoluble in water.
Fats and oils have higher boiling points so at room temperature they cannot absorb enough heat to evaporate. When fat or oil is place on a sheet of paper, it diffracts light. The diffracted light can pass from one side of the paper to another side and produces a translucent spot.
Acrolein test is used to detect the presence of glycerol or fat. When fat is treated strongly in the presence of a dehydrating agent like potassium bisulphate (KHSO4), the glycerol portion of the molecule is dehydrated to form an unsaturated aldehyde, acrolein that has a pungent irritating odour.
This test is used to detect the presence of seasame oil. Seasame oil gives a characteristic rose red colour with concentrated hydrochloric acid and furfural solution. Vanaspati ghee contains 5% seasame oil while pure desi ghee does not contain seasame oil. So this test can be applied to find out whether the given sample of desi ghee contains vanaspati ghee or not.
This test is used to detect the degree of unsaturation in oil or fat. Huble’s reagent reacts with alcoholic solution of iodine that contains some mercuric chloride. During the reaction, the violet colour of iodine fades away if the oil or fat is unsaturated. If the oil or fat is saturated, the violet colour of iodine does not fade away.