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PREFACE

FOOD is essential for nourishment and sustenance of life. Adulteration of food cheats the consumer and can pose serious risk to health in some cases. Food adulteration is thus a punishable offence under the provisions of Prevention of Food Adulteration Act, 1954 and the Rule made thereunder. Consumer awareness of quality of food and alertness in detecting common types of food adulteration can thus help in arresting this menace and enable Government to achieve the objective of Health for all by 2000 A. D.

The purpose of this booklet is to give the consumer an opportunity to detect a few common adulterants in food. These tests will simply help the consumers to screen their day-to-day food articles. But for detailed conformatory test and quantification under P. F. A. Act the analysis in a laboratory is must.

A simple kit for testing of such adulterants can be made by using apparatus and common reagents, list of which is at Appendix-II.

Name of Food Article
Adulterant
Test for adulterants
Remarks
Milk
Water
The Lactometer reading shall not ordinarily be less than 26.
Lactometer is marked in degrees ranging from 0-40.
   
The presence of water can be detected by putting a drop of milk on a polished slanting surface. The drop of pure milk either stops or flows slowly leaving a white trail behind it, whereas milk adulterated with water will flow immediately without leaving a mark.
The test is not valid if skimmed milk of other thickening material is added.
 
Starch
Add a few drops of tincture of Iodine or Iodine solution. Formation of blue colour indicates the presence of starch.
 
 
Removal of Fat
The lactometer reading will go above 26 while the milk apparently remains thick.
 
Khoa and it products
Starch
Boil a small quantity of sample with some water, cool and add a few drops of Iodine solution. Formation of blue colour indicates the presence of starch.
 
Chhana or Paneer
Starch
Boil a small quantity of sample with some water, cool and add a few drops of Iodine solution. Formation of blue colour indicates the presence of starch.
 
Ghee and Butter
Vanaspati or Margarine
Take about one teaspoon full of melted sample of Ghee / Butter with equal quantity of concentrated Hydrochloric acid in a stoppered test tube and add to it a pinch of sugar. Shake well for one minute and let it stand for five minutes. Appearance of crimson colour in lower (acid) layer shows presence of Vanaspati or Margarine.
The test is specific for seasame oil which is compulsorily added to Vanaspati and Margarine. Some coal tar colours also gives a positive test.
If the test is positive i.e red colour develops only by adding strong Hydrochloric acid (without adding crystals of sugar) then the sample is adulterated with coal tar dye.
 
Mashed Potatoes, Sweet Potatoes and other starches
The presence of mashed potatoes and sweet potatoes in a sample of Ghee / Butter can easily be detected by adding a few drops of Iodine Solution. When Iodine, which is brownish in colour turns to blue then mashed potatoes / sweet potatoes or starches are present.
 
Oils and Fats
Argemone oil
Take a small quantity of oil in a test tube. Add equal quantity of concentrated Nitric acid and shake carefully. Red to reddish brown colour in lower (acid) layer would indicate the presence of Argemone oil.
Colourless (not yellowish) Nitric acid may be used. Artificial colour if present will usually be a bright shade of colour, generally red or pink. The test may sometimes give misleading. The test may not respond if the Argemone oil is present in small quantity.
 
Mineral oil
Take 2 ml of the oil sample and add an equal quantity of N/2 Alcoholic potash. Heat in boiling water bath (dip in boiling water) for about 15 minutes and add 10 ml of water. Any turbidity shows presence of mineral oil.
If mineral oil is present in small quantity, this test may not be positive.
 
Castor oil
Take about 1 ml of the oil, add 10 ml of acidified petroleum ether and mix well. Add a few drops of ammonium molybdate reagent. Immediate appearance of white turbidity indicates the presence of castor oil.
If castor oil is present in small quantity, this test may not be positive.
Sugar
Chalk powder
Dissolve 10 gm of sugar in a glass of water, allow it to settle. Chalk will settle down at the bottom.
 
 
Washing soda
Take small quantity of sugar, dissolve it in water and add few drops of Hydrochloric acid, effervescence (gives off bubbles) will indicate the presence of washing soda.
 
Honey
Sugar solution
A cotton wick dipped in pure honey when lighted with a match stick burns and shows the purity of honey. If adulterated, the presence of water will not allow the honey to burn. If it does, it will produce a cracking sound.
This test is only for added water.
Sweets, Icecreams and beverages
Metanil yellow (a non permitted coal tar colour
Extract colour with luke-warm water from food articles. Add few drops of concentrated Hydrochloric acid. If magenta red colour develops the presence of metanil yellow is indicated.
 
 
Saccharin
Taste a small quantity. Saccharin leaves a lingering sweetness on tongue for a considerable time and leaves bitter taste at the end.
Take two spoons of liquid sample or about 5 to 10 gms of solid sample with little quantity of water in a test tube and add few drops of Hydrochloric acid and 10 ml of solvent ether. Shake well. Decant the ether layer into a test tube or a beaker, evaporate the ether spontaneously. Add one drop of water (warm) to the residue and taste. Sweet taste will indicate the presence of saccharin.
See Appendix-II
 
Aluminium foil
Aluminium foil is whitish grey in colour and is readily soluble in concentrated Hydrochloric acid while pure silver foil is not.
 
Wheat, Rice, Maize, Jawar, Bajra, Chana, Barley, etc.
Dust, pebble, stone, straw, weed seeds, damaged grain, weevilled grain, insects, rodent hair and excreta.
These may be examined visually to see foreign matter, damaged grains, discoloured grains, insect, rodent contamination etc.
Damaged / discoloured grains should be as low as possible since they may be affected by fungal toxins, Argemone seeds, Dhatura seeds etc. In moderately excessive amount can result in risk to health. Discard the damaged / undesirable grains before use.
 
Ergot (a fungus containing poisonous substance)
Purple black longer sized grains in Bajra shows the presence of Ergots.
Put some grains in a glass tumbler containing 20 percent salt solution. Ergot floats over the surface while sound grains settle down.
 
 
Dhatura
Dhatura seeds are flat with edges with blackish brown colour which can be separated out by close examination.
 
 
Karnel Bunt
The affected wheat karnel have a dull appearance, blackish in colour and rotten fish smell.
 
 
Argemone seed
Assemble mustard seed but shows a protrusion on close examination. The surface of argemone seed is grainy and rough while that of mustard seed is smooth. When mustard seed is pressed, inside it is yellow whereas argemone seed is white.
 
Parboiled Rice
Metanil yellow
Rub a few grains in the palms, yellow colour would get reduced or disappear. Add a few drops of dilute Hydrochloric acid to a few rice grains mixed with little water, presence of pink colour indicates, presence of Metanil yellow.
 
 
Turmeric
Take a small amount of sample in a test tube, add some water and shake. Dip Boric acid paper (filter paper dipped in Boric acid solution), if it turns pink, turmeric is present.
See Appendix-I
Dal whole and spilt
Khesari Dal
Add 50 ml of dilute Hydrochloric acid to the sample and keep on simmering water for about 15 minutes. The pink colour developed indicates the presence of khesari dal.
The test is only for khesari dal. (Metanil yellow if presents will give a similar colour immediately even without simmering)
 
Clay, stone, gravels, webs, insects, rodent hair and excreta
Visual examination will detect these adulterants.
Reject if the number of insects is large or if the odour is unpleasant and taste bitter or gritty.
 
Metanil yellow
Take 5 gms of the sample with 5 ml. of water in a test tube and add a few drops of concentrated Hydrochloric acid. A pink colour shows the presence of Metanil yellow.
 
Atta, Maida, Suji (Rawa)
Sand, soil, insects, webs, lumps, rodent hair and excreta
These can be identified by visual examination.
 
 
Iron fillings
By moving a magnet through the sample, iron fillings can be separated.
 
Besan
Khesari flour
Add 50 ml of dilute Hydrochloric acid to 10 gms of the sample and keep on simmering water for about 15 minutes. The pink colour developed indicates the presence of khesari flour.
 
Whole spices
Dirt, dust, straw, insect, damaged seeds, other seeds, rodent hair and excreta
These can be examined visually.
 
Black pepper
Papaya seeds
Papaya seeds can be separated out from pepper as they are shrunken, oval in shape and greenish brown or brownish black in colour.
 
 
Light black pepper
Float the sample of black pepper in alcohol. The mature black pepper berries sink while the papaya seeds and light black pepper float.
 
 
Coated with mineral oil
Black pepper coated with mineral oil gives Kerosene like smell.
 
Cloves
Volatile oil extrated (exhausted cloves)
Exhausted cloves can be identified by its small size and shrunken appearance. The characteristic pungent taste of genuine cloves is less pronounced in exhausted cloves.
 
Mustard seed
Argemone seed
Mustard seeds have a smooth surface. The argemone seed have grainy and rough surface and is black and hence can be separated out by close examination. When mustard seed is pressed, inside it is yellow while for argemone seed it is white.
Use magnifying glass for identification.
Powdered spices
Added starch
Add a few drops of tincture of Iodine or Iodine solution. Formation of blue colour indicates the presence of starch.
Iodine test for added starch is not applicable for turmeric powder.
 
Common salt
Taste for addition of common salt.
 
Turmeric powder
Coloured saw dust
Take a teaspoon full of turmeric powder in a test tube. Add a few drops of concentrated Hydrochloric acid. Instant appearance of pink colour which disappear on dilution with water shows the presence of pure turmeric. If the colour persists, metanil yellow is present.
This test is only for Metanil yellow.
 
Chalk powder or yellow soap stone powder
Take a small quantity of turmeric powder in a test tube containing small quantity of water. Add a few drops of concentrated Hydrochloric acid, effervescence (give off bubbles) will indicate the presence of chalk or yellow soap stone powder.
 
Chillies powder
Bricks powder, salt powder or talc powder
Take a teaspoon full of chillies powder in a glass of water. Coloured water extract will show the presence of artificial colour. Any grittiness that may be felt on rubbing the sediment at the bottom of glass confirms the presence of brick powder / sand, soapy and smooth touch of the white residue at the bottom indicates the presence of soap stone.
This test is only for earthy materials.
 
Water soluble coal tar colour
Water soluble artificial colour can be detected by sprinkling a small quantity of chillies or turmeric powder on the surface of water contained in a glass tumbler. The water soluble colour will immediately start descending in colour streaks.
 
 
Oil soluble coal tar colour
Take 2 gms of the sample in a test tube, add few ml of solvent ether and shake. Decant ether layer into a test tube containing 2 ml of dilute Hydrochloric acid (1 ml HCL plus 1 ml of water). Shake it, the lower acid layer will be coloured distinct pink to red indicating presence of oil soluble colour.
See also Appendix-I
Hing
Soap stone or other earthy matter
Shake little portion of the sample with water and allow it to settle. Soap stone or other earthy matter will settle down at the bottom.
In compounded Hing due to presence of starch a slight turbid solution may be produced. However, this will settle down after keeping.
Saffron
Dried tendrils of maize cob
Genuine saffron will not break easily like artificial. Artificial saffron is prepared by soaking maize cob in sugar and colouring it with coal tar colour. The colour dissolves in water if artificially coloured. A bit of pure saffron when allowed to dissolved in water will continue to give its saffron colour so long as it lasts.
 
Common salt
White powdered stone
Stir a spoonful of sample of salt in a glass of water. The presence of chalk will make solution white and other insoluble impurities will settle down.
 
Tea leaves
Exhausted tea or tur or gram dal husk with colour
Take a filter paper and spread a few tea leaves. Sprinkle with water to wet the filter paper. If coal tar colour is present it would immediately stain the filter paper. Wash the filter paper under tap water and observe the stains against light.
 
   
Spread a little shaked lime on procelain tile or glass plate. Sprinkle a little tea dust on the lime. Red, orange or other shades of colour spreading on the lime will show the presence of coal tar colour. In case of genuine tea, there will be only a slight greenish yellow colour due to chlorophyl, which appear after sometime.
 
 
Iron fillings
By moving a magnet through the sample, iron fillings can be separated.
 
Coffee
Chicory
Gently sprinkle the coffee powder sample on the surface of water in a glass. The coffee floats over the water but chicory begins to sink down within a few seconds. The falling chicory powder particles leave behind them a trail of colour, due to large amount of caramel.
 
 
Tamarind seeds powder and Date seeds powder
Sprinkle the suspected coffee powder on white filter / blotting paper and spray 1 percent sodium carbonate solution on it. Tamarind and date seed powder will stain filter / blotting paper red.
 
Pan Masala
Colour and Saccharin
Colour dissolves in water.
Saccharin gives excessive and lingering sweet taste and leaves bitter taste at the end.
 
Catachu powder
Chalk
Chalk gives effervescence (gives off bubbles) with concentrated Hydrochloric acid.
This test is only for chalk.
Silver leaves
Aluminium leaves
On ignition, genuine silver leaves burn away completely, leaving glistering white spherical ball of the same mass whereas aluminium leaves are reduced to ashes of dark grey blackish colour.
Take silver leaves in test tube, add diluted Hydrochloric acid. Appearance of turbidity to white precipitate indicates the presence of silver leaves. Aluminium leaves do not give any turbidity or precipitate.
Take a small portion of metal leaves and add a few drops of concentrated Nitric acid. Silver leaves will completely dissolve whereas aluminium leaves will remain undissolved.
 
Vinegar
Mineral acid
Test with the Metanil yellow indicator paper. In case, the colour changes from yellow to pink, mineral acid is present.
See Appendix-I

APPENDIX-I

METHOD FOR TEST

1. Test for Metanil Yellow : Take some sample in a test tube and add some amount of water, shake well. Add few drops of diluted Hydrochloric acid. Violet colour in the water portion indicates the presence of Metanil Yellow.

2. Test for Starch : Boil the sample with some water in a test tube, cool and add a few drops of Iodine solution. Appearance of blue colour indicates the presence of Starch.

3. Baudouin test : Take about one teaspoon full of melted Ghee / Butter with equal quantity of concentrated Hydrochloric acid in a test tube and add a pinch of sugar to it. Shake well and allow to stand. Appearance of crimson red colour shows the presence of Vanaspati or Margarine.

4. Boric acid test for Turmeric : Take a small amount of sample in a test tube, add some water and shake. Dip Boric acid paper. If it turns pink, turmeric is present. (Boric acid paper can be prepared by dipping a strip of filter paper in the Boric acid solution. Boric acid solution can be prepared by dissolving 5 gms of Boric acid in 100 ml concentrated Hydrochloric acid.)

5. Metanil yellow indicator paper : Metanil yellow indicator paper can be prepared by dipping a strip of filter paper in Metanil yellow solution (1 gm Metanil yellow coal tar colour dissolved in 100 ml of water).

6. Oil soluble coal tar colour : Take a small quantity of chillies powder in a beaker and add 5 ml of rectified sprit (alcohol). Dip a small piece of white silk cloth for two minutes. Remove the silk cloth piece and wash with water. If the silk cloth is permanently dyed, it indicates the presence of oil soluble coal tar colour.

APPENDIX-II

LIST OF APPARATUS AND REAGENTS FOR DEVELOPING A SIMPLE KIT

APPARATUS :

1. Magnifying Glass
2. Spatula
3. Magnet
4. Forcep
5. Lactometer
6. Beaker
7. Dishes
8. Dropper
9. Reagent Bottles
10. Spirit lamp
11. Test tube ordinary
12. Test tube stoppered
13. Glass rod
14. Test tube stand
15. Small plastic tray (White)
16. Porcelain tile (White)
17. Glass Cylinder
18. Glass Marking pen
19. Filter paper
20. White silk cloth
21. Cotton

REAGENTS :

1. Hydrochloric acid
2. Nitric acid
3. Petroleum ether
4. Solvent ether
5. Rectified spirit
6. Iodine / Tincture of Iodine
7. Potassium Hydroxide
8. Ammonium Molybdate
9. Boric Acid
10. Sodium Carbonate
11. Metanil yellow powder

PRECAUTION TO BE TAKEN

CAUTION :

1. The testing kit should be kept beyond the reach of children as it contains harmful chemicals.

2. Solvent ether is highly inflamable. Keep it away from fire. Don't keep the bottle's cap open.

3. Acids are highly corrosive. In case of acid burn wash immediately with cold water containing sodium bicarbonate.

4. Use gloves while performing the tests.


In case of further clarification regarding tests, Contact : Director, Central Food Laboratories, Ghaziabad, Kolkata, Mysore, Pune or Assistant Director General (PFA), Directorate General of Health Services, Nirman Bhavan, New Delhi - 110011, INDIA.