Home » ADULTERATION TEST » QUICK TESTS FOR SOME ADULTERANTS IN FOOD

QUICK TESTS FOR SOME ADULTERANTS IN FOOD

                                                                                                                     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 Rules made thereunder. Consumer awareness of quality of food and alertness in detecting common types of food adulteration can help in arresting this menance and enable Government to achieve the objective of ‘Health for All by 2000 A.D.*

The purpose of this web site 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 qualification 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.

( 1  ) . M I L K  &  M I L K   P R O D U C T S

Name of Food Article Adulterant

Simple Method for detection of Common Adulterants

Remarks

i. Milk

Water

i. The lactometer reading shall not ordinarily be less than 26.

ii. 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.

Add a few drops of tincture of lodine or lodine solution. Formation of bvlue colour indicates the presence of starch.

    Lactometer is marked in degrees ranging from 0-40.

The test is not valid if skimmed milk or other thickening material is added.

starch

   Add a few drops of tincture of lodine or lodine 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.

ii. Khoa and its products Starch

Boil a small quantity of sample with some water, cool and add a few drops of lodine solution. Formation of blue colour indicates the presence of starch.

iii. Chhana or Panner Starch

Boil a small quantity of sample with some water, cool and add a few drops of lodine solution. Formation of blue colour indicates the presence of starch.

iv. Ghee Vanaspati or MargarineMashed Potatoes, Sweet Potatoes and other starches.

Take about one tea spoon full of melted sample of Ghee 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 presence of mashed potatoes and sweet potatoes in a sample of Ghee can easily be detected by adding a few drops of lodine, when lodine, which is brownish in colour turns to blue then mashed potatoes/ sweet potatoes/other starches are present.

The test is specific for sesame oil which is compulsorily added to Vanaspati and Margarne. Some coal tar colours also give 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. If the crimson or red colour develops after adding and shaking with sugar, then alone Vanaspati or Margarine is present.

v. Butter Vanaspati or margarine

Mashed Potatoes, Sweet Potatoes and other starches.

Take about one tea spoon full of melted sample of Ghee with equal quantity of concentrated Hydrochloric acid in a stoppered test tube and add to it a pinch of sugar. Shake wel 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 presence of mashed potatoes and sweet potatoes in a sample of Ghee can easily be detected by adding a few drops of lodine, when lodine, which is brownish in colour turns to blue then mashed potatoes/ sweet potatoes/other starches are present.

The test is specific for sesame oil which is compulsorily added to Vanaspati and Margarne. Some coal tar colours also give a positive test.

vi. OILS AND FATS Argemone oil

Take 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 should  be used. Artificial colour if present will usually be a bright shade of colour, generally red or pink. The test may sometimes give misleading result. 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 one ml of the oil, add 10 ml of acedified pertroleum ether and mix well. Add a few drops of ammonium molybdate reagent. lmmediate apprearance of white turbidity indicates the presence of castor oil. If   Castor oil is present in small quantity this test may be positive.

( 2 ) . S W E E T I N G   A G E N T S

Name of Food Article Adulterant

Simple Method for detection of Common Adulterants

Remarks

i. Sugar Chalk powder Dissolve 10 gm of sample in a glass of water, allow to settle. Chalk will settle down at the bottom.
ii. Pithi Sugar Washing soda

Chalk powder

Add few drops of Hydrochloric acid, effervescence (give off bubbles) will indicate the presence of washing soda.

Dissolve 10 gm of sample in a glass of water, allow to settle, chalk will settle down at the bottom

 
iii. 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 n ot allow the honey to burn. If it does, it will produce a cracking sound. This test is only for added water.
iv. Sweetmeats, Icecream and beverages Metanil yellow (a non-permitted coal tar colour) Extract colour with luke-warm from food articles. Add few drops of concentrated Hydrochloric acid. If magenta red colour develops the presence of metanil yellow is indicated.
 

 

 

 

 

Silver foil

Saccharin

Aluminium foil

i. Taste a small quantity. Saccharin leaves a lingering sweetness on tongue for a considerable time and leaves a bitter taste at the end.

ii. Take two spoons of liquid sample or about 5 to 10 gms of solid sample with little quantity of water in a test tube, 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.

Aluminium foil is whitish grey in colour and is readily soluble in concentrated Hydrochloric acid while pure silver foil is not.

See Appendix-II.

( 3 ) . FOODGRAINS AND THEIR PRODUCTS

Name of Food Article Adulterant

Simple Method for detection of Common Adulterants

Remarks

i. 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/ undsirable grains before use.
Ergot (a fungus containing poisonous substance) a. Purple black longer sized grains in Bajra show the presence of Ergots. b. Put some grains in a glass tumbler containing 20 per cent 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 separted out by close examination.

Kamel Bunt

   The affected wheat kernel have a dull appearance, blackish in colour and rotten fish smell.
Argemone seed Assemble mustard seed but show a protrusion on close examination. The surface ofAgemone seed is grainy and rough while that of mustard seed is smooth.When Mustard seed is pressed in side, it is yellow whereas Argemone seed is white.
ii. Sella Rice (Parboiled Rice) Metanil yellow (a non-permitted coal tar colour) Rub a few grains in the palms of two hands. Yeellow 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 indicate presenc of Metanil yellow.
Turmeric (colouring for golden appearance) 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
iii. Dal whole and spilt Khesari Dal

Clay, stone, gravels, webs, insects, rodent hair and excreta.

i. Khesari dal has edged type appearance showing a slant on one side and square in appearance in contrast to other dals.

ii. Add 50ml of dilute Hydrochloric acid to the sample and keep on simmering water for about 15 minutes. The pink colour developed indicates the present of Khesari dal (1:6 HCl).

Visual examination will detect these adulterants.

The Test is only for Khesari dal (Matenil yellow if present will give a similar colour immediately even without simmering).

Reject if the number of insects is large or if the odour is unpleasant and teste bitter or gritty.

Metanil yellow (a non-permitted coaltar colour) Take 5 gms of the sample with 5ml. of water in a test tube and add a few drops of concentrated Hydrochloric acid. A pink colour shows presence of Metanil yellow.
iv. Atta Maida, Suji (Rawa) Sand, soil, insects, webs, lumps, rodent hair and excreta.

Iron filings

These can be identified by visual examination.

By moving a magnet through the sample, iron filings can be separated.

v. Besan Khesari Flour Add 50ml of dilute Hydrochloric acid to 10gms. of sample and keep on simmering water for about 15 minutes. The pink colour, if developed, indicates, the presence of Khesari flour. The test is only for Khesari dal (Metanil yellow, if present will give a similar colour even without simmering).

 

( 4 ) . SPICES AND CONDIMENTS

Name of Food Article Adulterant

Simple Method for detection of Common Adulterants

Remarks

i. Whole spices Dirt, dust, straw, insect, damaged seeds, other seeds, rodent hair and excreta. These can be examined visually.
a.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 (rectified spirit). The mature black pepper beries sink while the papaya seeds and light black pepper float.
Coated with mineral oil Black pepper coated with mineral oil gives Kerosene like smell.
b.Cloves Volatile oil extracted (exhausted cloves) Exhausted cloves can be identified by its small size and shrunken appearance. The characteristic pungent tests of genuine cloves is less pronounced in exhausted cloves.
c. Mustard seed Argemone seed Mustard seeds have a smooth surface. the argemone seed have grainy and rough surface and are 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.
ii.Powdered spices Added starch

Common Salt

Add a few drops of tincture of lodine or lodine solution. Indication of blue colour shows the presence of starch.

Taste for addition of common salt.

Iodine test for added starch is not applicable for turmeric powder.
a. Turmeric powder Coloured saw dust

Chalk powder or yellow soap stone powder

Take a tea spoon full of turmeric powder in a test tube. Ad a few drops of concentrated Hydrochloric acid. Instant appearance of pink colour which disappears on dilution with water shows the presence of turmeric. If the colour persists, metanil yellow (an artificial colour) a non-permitted coal tar colour is present.

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.

This test is only for Metanil yellow.
b. Chillies powder Brick Powder, salt powder or talc powder.

Water soluble coal tar colour

Take a tea spoon full of chillies powder in a glass of water. Coloured water extract will show the presence of articficial colour. Any grittingess 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.

Water soluble artificial colour can be detected by sprinkling s 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.

This test is only for earthy material.
Oil solube coat tar colour Take 2 gms of the samples in a test tube, add few ml of solvent ether and shake, Decant ether layer into a test tube containing 2ml of dilute Hydrochloric acid (1 ml HCl plus 1ml of water). Shake it, the lower acid layer wil be coloured distinct pink to red indicating presence of oil soluble colour. See also Appendix-I.
iii. Hing Soap stone or other earthy matter Shake little portion of the sample with water and allow 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.
iv. Saffron Dried tendrils of maize cob Genuine saffron will not break easily like artificial. Artificial

( 5 ) . MISCELLANEOUS FOODS

Name of Food Article Adulterant

Simple Method for detection of Common Adulterants

Remarks

Common Salt

Tea Leaves

Coffee

White powdered stone

Exhausted tea or tur or gram dal husk with colour

Iron filings

Chicory

Tamarind seeds powder and date seed powder

saffron is prepared by soaking maize cob in sugar and colouring it with coal tar colour. the colour dissolves in after 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.

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.

Take a filter paper and spread a few tea leaves. Sprinkle with water to wet the filter paper. If coal tar immediately stain the filter paper. Wash the filter paper under tap water and observe the stains against light.

Spread a little slaked lime on white porcelain 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 chlorophyll, which appear after some time.

By moving a magnet through the sample, iron fillings can be separated.

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.

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, if present, stain blotting paper/filter paper red.

Supari Pan Masala

Catachu Powder

Silver Leaves

Colour

Saccharin

Chalk

Aluminium leaves

Colour dissolves in water.

Saccharin gives excessive and lingering sweet taste and leaves bitter taste at the end.

Chalk gives effervescence (gives off bubbles) with concentrated Hydrochloric acid.

i. 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.

ii. 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.

iii. 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.

This test is only for chalk.

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

METHOD FOR TEST

1. Test for Metanil Yellow : Take some samaple 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. Baudoium Test : Take about one tea spoon full of melted ghee or butter with equal quantity of concentrated hydrochloric acid in a test tub and add to it a pinch of sugar. Shake well and allow to stand. Appearance of crimson red colour shows the presence of vanaspati of 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 provided in the kit. Boric Acid solution can be prepared by dissolving 5 gms of boric acid in 100ml concentrated Hydrochloric acid.

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

6. Oil Soluble coal tar colour : Take a small quantity of chillies powder in a beaker and add 5ml of rectified spirit (alcohol). Dip a small piece of white silk for two minutes. Remove the silk piece and wash with water. If the silk cloth is permanently dyed, it indicates the presence of oil soluble coat 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. Petri 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 pencil
19. Filter paper
20. White silk cloth
21. Cotton

REAGENTS:

1. Hydrochloric acid
2. Nitric Acid
3. Petroleum ether
4. Solvent ether
5. Rectified sprit
6. Iodine/Tincture of iodine

7. Potassium Hydroxide
8. Ammonium Molybdate
9. Boric Acid
10. Sodium Carbonate
11. Metanil Yellow powder

PRECAUTIONS TO BE TAKEN
CAUTION:

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

2. Solvent ether is highly inflammable. Keep it away from fire.

3. Acids are highly corrosive. In case of acid burn, wash immediately with cold water containing sodium bicarbonate (Meetha Soda).

4. Use gloves while performing the tests.

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