Food adulteration has now become a burning problem. The adulterants used are so similar to natural foodstuffs that it becomes very difficult for a common man to detect them. A few simple tests can be done to detect adulterants found in common foodstuffs.
1. Stone chips in Rice
Place the rice grains on the palm of the hand and gradually immerse the hand in water. The stone chips will sink.
2. Metanil yellow in pulses
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Shake 5 gms: of the suspected pulses with 5 ml of water. Add a few drops of hydrochloric acid. A pink colour shows the presence of metanil yellow.
3. Kesari Dal in Channa or Other Dals
Add 5 ml of normal hydrochloric acid to a small quantity of dal in a glass. Keep the glass in simmering water for 15 minutes. Development of pink colour indicates the presence of Kesari dal. By visual detection-shape of dal. The kesari dal is wedge shaped.
4. Ergot in Bajra seeds
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Put some grains in a glass containing 20% salt solution. Ergot will float on the surface while sound bajra seeds will sink.
5. Coal-tar dye in Roasted Gram
The colour is obviously visible.
6. Iron filings in Rawa (Sooji)
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Pass a magnet through the rawa. The iron filing will cling to it.
7. Water in milk:
Measure the specific gravity with a lactometer. The normal values will fall between 1.030 and 1.034. Milkmen are wise to the test and may dilute the milk only to the right density, so this is only a rough test.
8. Starches in milk:
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Add a drop of iodine solution to a small quantity of milk. Milk containing starch turns blue. Pure milk turns a coffee shade.
9. Vanaspati in pure ghee
Take about one teaspoonful of melted butter with an equal quantity of concentrated hydrochloric acid in a test tube. Add 2 or 3 drops of furfural solution. Shake it well for one minute and let it stand for five minutes. Appearance of pink colour in the lower layer of acid means that vanaspati is present in pure ghee/butter as an adulterant.
10. Mashed potatoes, sweet potatoes and other starches in butter
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Perform the Iodine test for starch.
11. Cheap edible oils in Vanaspati
Add a solution of washing soda to the sample of vanaspati and shake it in a test tube. If froth appears on the top, it may be inferred that cheap oil has been added to vanaspati.
12. Argemone oil in mustard oil
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Heat the mixture of oils with a little amount of nitric acid for two to three minutes. A red colour will appear if argemone is present.
13. Artificial dye in tea leaves
Deposit the tea leaves on a moistened blotting paper. Artificially dyed tea leaves will impart colour to the moistened blotting paper immediately.
14. Powdered date seeds or tamarind powder in coffee
Sprinkle a little coffee powder on a piece of blotting paper and spread a few drops of potassium hydroxide solution over this paper. If a brown colour emerges around the particles of coffee, adulteration is established.
15. Chicory in Coffee Powder
Sprinkle a small quantity of coffee powder on the surface of water in a glass tumbler. Particles of genuine coffee powder will float, but chicory particles will begin to sink within seconds. They will also leave a stain of colour in the water.
16. Chalk or any other dust or dirt in sugar
Dissolve sugar in water, the impurities will settle down at the bottom.
17. Jaggery with Metanil yellow
Hydrochloric acid added to a solution of the jaggery will turn it magenta red.
18. Bura sugar with washing soda
Gives off everscence with hydrochloric acid.
19. If dissolved in water, the washing soda will turn red litmus into blue.
20. Extraneous colouring matter in turmeric or chilly powder.
Sprinkle a small quantity of powder on the surface of water contained in a glass tumbler. The extraneous colour will dissolve.
Mix a small quantity of red chilly powder in ether. Take the extract. Add concentrated hydrochloric acid. A dark pink colour appears if the sample is adulterated.
21. Grit, clay, extraneous matter in common salt
Dissolve salt in some water in a glass tumbler. Pure salt will completely dissolve in it, whereas extraneous matter contained therein will be seen changing into solution or will settle down at the bottom as a deposit.
22. Grit in spices
The powdered spices dissolve in carbon tetrachloride. In water, the spices will float and grit will settle down at bottom.
23. Resin or gum or colour in asafetida
Pure asafoetida dissolves in water to form a milky solution.
Pure asafoetida burns with a bright flame on ignition.
24. Talc powder in cardamom
Essential oil is removed from the cardamom. It is then rubbed with talc powder to look fresh. The talc powder will stick to the fingers. On tasting, if any aromatic taste is present it indicates the removal of essential oil.