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In this article we will discuss about the tests for detection of fats and oils in plants with the help of experiments.
Fats and Oils are invariably present in all living cells. They are synthesized through an active metabolism and also serve a number of indispensable roles in physiological processes.
Fats are the esters of fatty acids with glycerol and contain the elements C, H and O as do the carbohydrates; but the proportion of carbon to oxygen is much greater in fats than in carbohydrates. Fats are insoluble in water, but soluble in a number of organic solvents. They can be easily hydrolysed by alkali treatment.
Requirements for Detecting Fats and Oils in Plants:
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(a) Preparation of Sample:
As the fats are insoluble in water, they are found in the protoplasts of plant cells as small droplets or globules, which can be micro-chemically stained and examined under microscope. Oils, as such, could be extracted from plant materials on crushing and used for chemical tests.
(b) Reagents:
1. Sudan III stain: (0.5% in 70% alcohol).
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2. Osmic acid (1%).
3. Solvents like ether, alcohol, chloroform
4. NaOH solution (10%).
5. Na2SO4 solution.
6. Dilute H2SO4.
7. KHSO4 solution.
8. Dilute CuSO4 solution.
Tests of Fats and Oils:
Experiment:
1. Micro Chemical Tests on Sections of Plant Materials :
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(a) A thin section of onion scale or a fatty seed is placed on a glass slide and then a drop of Sudan III soln. is added and allowed to stand for 20min. Then the section is washed with 50% alcohol and mounted in glycerine.
(b) The said section is stained with 1% Osmic acid for 1-2 mins.
2. Solubility Test:
Oil is added to various solvents (water, ether, alcohol, chloroform) and thoroughly shaken for 2-5 mins and allowed to stand for 1-2 mins.
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3. Saponification Test:
About 100 ml of olive oil is added to about 250 ml of 10% NaOH solution. Boil for half an hour in a water bath and, after cooling, add excess of Ng2SO4 solution.
The reaction mixture is filtered to remove the soap. The filtrate is then treated with dilute H2SO4. The liquid is evaporated and the residue treated with alcohol.
This dissolves the glycerol thus formed which may be detected by the following tests:
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(a) To a little of the above liquid solution a few crystals of KHSO4 are added and heated strongly.
(b) To a little of the liquid solution a few drops of CuSO4 soln. and NaOH soln. are added.
Observation:
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Red stained oil droplets which can be seen floating around the section as well as in the cells of the sections.
Black-stained drops appear in the cells.
Oil is insoluble in water and alcohol, but soluble in ether and chloroform.
The soap formed thus separates out and rises to the surface.
Pungent odour of acrylic aldehyde is detected.
A clear blue soln. is obtained.
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Inference:
Presence of fats and oils in the plant material.
Presence of fats and oils in the plant tissue.
Presence of oil in the sample.
Presence of fats and oils in the sample.
Presence of glycerol. Presence of glycerol.
