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Methods for Detection of common adulterants in food

This topic covers the Information related to the Methods for Detection of common adulterants in food

Milk and Milk Products

S.No Food Article Adulterant Method for Detection Remarks
1 Milk water The presence of water can be by putting a drop of milk on a polished slanting surface. The drop of pure milk either or flows lowly leaving a white trail behind it, whereas milk adulterated water will flow immediately without leaving a mark
2 Starch Add a few drops of tincture of Iodine or Iodine solution. Formation of blue colour indicates the presence of starch. Iodine solution is easily available in the medical
stores.
3 Urea Take a teaspoon of milk in a test tube. Add ½ teaspoon of soybean or arhar powder. Mix up the contents thoroughly by shaking the test tube. After 5 minutes, dip a red litmus paper in it. Remove the paper after ½ a minute. A change in colour from red to blue indicates the presence of urea in the milk.
4 Vanaspati Take 3 ml of milk in a test tube. Add 10 drops of hydrochloric acid. Mix up one teaspoonful of sugar. After 5 minutes, examine the mixture.The red colouration indicates the presence of vanaspati in the milk.
5 Formalin Take 10 ml of milk in a tests tube and add 5 ml of conc. sulphuric acid from the sides of the wall without shaking. If a violet or blue ring appears at the intersection of two layers then it shows presence of formalin. Formalin enhances the life of milk and thus is
added for preservation
purpose.
6 Detergent Shake 5-10 ml. of sample with an equal amount of water lather indicates the presence of detergent.
7 Milk Synthetic milk Synthetic milk has a bitter after taste, gives a soapy feeling on rubbing between the fingers and turns yellowish on heating.
8 Synthetic milk-test for protein The milk can easily be tested by Urease strips (available in the Medical stores) because Synthetic milk is devoid of protein.
9 Test for Glucose/
inverted sugar
Milk does not contain glucose /invert sugar, if test for glucose with urease strip found positive.It means milk is adulterated. If it is made synthetically by adding while colour water paint. Oils, alkali,
urea and detergent
etc. Glucose, inverted
sugar syrup is added in milk to increase the
consistency and test
10 Ghee, cottage
cheese, condensed
milk, khoa, milk
powder etc,
Coal Tar Dyes Add 5 ml of dil. H2SO4 or conc. HCL to one teaspoon full of melted sample in a test tube. Shake well. Pink colour (in case of H2SO4) or crimson colour (in case of HCl) indicates coal tar dyes. If HCl does not give colour dilute it with water to get the colour.
11 Sweet Curd Vanaspati Take1 teaspoon full of curd in a test tube. Add 10 drops of hydrochloric acid. Mix up the contents shaking the test tube gently. After 5 minutes, examine the mixture. The red colouration indicates the presence of vanaspati in the curd.
12 Rabri Blotting paper Take a teaspoon of rabri in a test tube. Add 3 ml of hydrochloric acid and 3 ml of distilled water. Stir the content with a glass rod. Remove the rod and examine. Presence of fine fibres to the glass rod will indicate the presence of blotting paper in rabri.
13 Khoa and
its 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.
14 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.

Oil and Fats

S. No Food Article Adulterant Method for Detection Remarks
1 Ghee Vanaspathy or Margarine 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 for one minute and let it for five minutes. Appearance of crimson colour in lower (acid) of Vanaspati or Margarine. The test is specific for seasame oil
Which is compulsorily added to Vanaspati and Margarine.
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
2 Mashed Potatoes, Sweet Potatoes and other starches. The presence of mashed potatoes and sweet potatoes in a sample of ghee can easily be detected by adding a few drops of Iodine, which is brownish in colour turns to blue if mashed potatoes/sweet potatoes/other starches are present.
3 Butter Vanaspati or Margarine Take about one teaspoon full of melted sample of butter with equal quantity of concentrated Hydrochloric acid in a stoppered test tube and add to it a pinch of sugar. Shake for one minute and let it for five minutes. Appearance of crimson colour in lower (acid) of Vanaspati or Margarine. The test is specific for seasame oil which is compulsorily added to Vanaspati and Margarine. Some coal tar colours also give a positive test.

If the testis 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
4 Mashed Potatoes and other starches The presence of mashed potatoes and sweet potatoes in a sample of butter can easily e detected by adding a few drops of iodine (which is brownish in colour), turns to blue.
5 Edible oil Prohibited colour
Take 5 ml of sample in a test tube and add 5 ml of concentrated hydrochloric acid. Shake gently, let it stand for 5 minutes. Colour will separate in the upper layer of the solution.
6 Coconut oil Any other oil Place a small bottle of oil in refrigerator. Coconut oil solidifies leaving the adulterant as a Separate layer.

Sweetening Agents

S. No Food Article Adulterant Method for Detection Remarks
1 Sugar Chalk powder Dissolve 10 gm of  sample in a glass of water,  allow  settling, Chalk will settle down at  the bottom.
2 Urea Dissolve 10 gm of  sample in a glass of water,  allow  settling,  Chalk  will  settle  down at  the bottom.
3 Chalk powder Dissolve 10 gm of  sample in a glass of water, allow to settle,chalk will settle down at  the bottom.
4 Yellow  colour (Non -permitted) Take 5 ml in a tests tube from the above solution and add a few drops of conc.  HCl. A pink colour in lower acid layers shows the presence of non- permitted colour.
5 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.
6 Jaggery Washing soda Add a few drops of solution HCl. Effervesence  shows  presence  of  washing soda.
7 Jaggery Chalk powder Dissolve a little amount sample in water in a test tube,chalk powder settles down.-Or- Add a few  drops of conc HCl solution,effervescence indicates  the  presence  of  adulterant.
8 Metanil yellow colour Take ¼ of a teaspoon of the jaggery in a test tube. Add 3 ml of alcohol and shake the tube vigorously to mix  up the content. Pour  10  drops  of hydrochloric acid in it. A pink colouration indicates the presence of metanil yellow colours in jaggery.
9 Sugar Solution Add a drop of honey to a glass if water, if the drop does not disperse in water it indicates that the honey is pure. However, if the drop disperses in water it indicates presence of added sugar.
10 Bura sugar Washing soda Add 1 ml of HCl to a little of bura sugar. Effervescence occurs if washing soda is present. Dissolve 2 gm of sugar in water; dip a red litmus paper in the solution. If washing soda is present, it will turn blue.
11 Sweetmeats, Ice-cream and beverages Metanil yellow (a non - permitted coal tar colour) Extract colour with luke-warm water from food articles. Add few drops of concentrated Hydro chloric acid. If magenta red colour develops the presence of metanil yellow is indicated. 
12 Saccharin i. Taste a small quantity. Saccharin leaves a lingering sweetness on tongue for a considerable time and leaves a bitter taste at the end.

Food grains and their products

S.No Food Article Adulterant Method for Detection Remarks
1 Wheat, Rice, Maize, Jawar, Bajra, Chana, Barley etc. Dust, pebble, Stone, Straw,weed seeds,damaged grain,weevilled grain, insects, hair and excreta of rodent 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
2 Maida Resultant atta or cheap flour When dough is prepared from resultant or left out atta, more  water has to be used. The normal taste of chapattis prepared out of wheat is  somewhat  sweetish  whereas  those  prepared  out  of  adulterated  wheat  will taste insipid.
3 Maida/ Rice Boric Acid Take a small amount of sample in  a test tube, add some water and  shake. Add a few drops of HCl. Dip a turmeric paper strip if it turns red, boric acid is present.
4 Wheat, bajra        and other grains Ergot (a fungus containing
poisonous substance)
(i)  Purple black longer sized  grains in Bajra  show the presence of Ergots.
(ii)  Put some grains In a glass  tumbler containing  20  per  cent  salt solution(20 gm common salt to  100 ml water)purple black longer size grain Ergot floats over  the surface while sound grains settle down.

5 Wheat, bajra and other grain Dhatura Dhatura seeds are flat with edges  with blackish brown colour which   can be separated out  by close examination.
6 Wheat, bajra and other grain Karnal Bunt The affected wheat kernel have a  dull appearance, blackish in colour and rotten fish smell,
7 Sella Rice (Parboiled Rice) Metanil yellow(a non-permitted coal tar colour) Rub a few grains in the palms of two  hands. Yellow 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
8
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
(ii) Take  some  rice  and  sprinkle on  it a small amount of soaked lime for  some time, grains will turn red if  turmeric is present.

9 Parched rice Urea Take 30 numbers of parched rice in a test tube. Add 5ml of distilled water in it.Mix up the contents thoroughly, by shaking the test tube. After 5 minutes, filter the water -contents, and add ½ teaspoon of powder of arhar or soybean in it. Leave it for  5 minutes, and then dip a red litmus paper in the mixture. Take out the litmus paper after 30 seconds and examine it. A blue colouration indicates the presence  of  urea in the parched rice.
10 Wheat flour Excess bran Sprinkle on water surface. Bran will float on the surface.
11 Wheat flour Chalk powder Shake sample with dil.HCl Effervescence  indicates chalk Chalk powder is used as an
adulterant due to its weight.
12 Dal whole
and spilt
Khesari Dal (i) Khesari dal has edged type appearance  showing a slant on one side and square in appearance in contrast to other daIs. 
(ii) Add 50 ml of  dilute Hydrochloric acid to the sample and keep on simmering  water for about 15minutes.The pink color developed indicates the presence  of Khesari dal.
The test is only for Khesari dal.(Metanil yellow if present will give a similar colour immediately even without simmering).
13
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
14
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 o Metanil yellow
15 Atta, Maida Suji (Rawa) Sand, soil, insects, webs, lumps. rodent hair and excrete These can be identified by visual examination.
16
Iron filings By moving a magnet through the sample, iron filings can be separated.
17 Bajra Ergot infested Bajra. Soak bajra in water, swollen and black Ergot infested grains will turn light in weight and will float in water
18 Sago Sand or talcum Put a little quantity of sago in mouth,it will have a gritty feel, if adulterated.Burn the sago,if  pure, it will swell and leave hardly any ash. Adulterated sago will leave behind  appreciable quantity of ash.
19 Besan Metanil Yellow Take ½ teaspoon of the besan in a test tube. Pour 3 ml of alcohol in the test tube. Mix up the contents thoroughly by shaking the test tube. Add 10 drops of hydrochloric acid it. A pink colouration indicates presence of metanil yellow in the gram  powder.
20
Khesari Flour Add 50 ml of dilute  Hydrochloric acid to 10 gms of s ample 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).
21 Pulses Lead Chromate Shake 5 gm.Of pulse with 5 ml. Of water and add a few drops of HCl. Pink colour indicates Lead Chromate.

Spices

S.No Food Article Adulterant Method for Detection Remarks
1 Whole spices Dirt, dust, straw, insect, damaged seeds, other seeds, rodent hair and
excrete
These can be examined visually
2 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.
3 Light black pepper Float the sample of black pepper in alcohol    (rectified spirit). The black pepper berries sink  while the papaya seeds and light black  pepper float. 
(ii) Press the berries with the help of fingers  light  peppers  will  break  easily  while  black  berries  of  pepper  will  not  break.
4 Coated with mineral oil Black pepper coated with mineral oil gives Kerosene like smell.
5 Cloves Volatile oil extracted
(exhausted cloves)
Exhausted  cloves  can  be  identified  by its small size and shrunken appearance.The characteristic pungent of genuine cloves is less pronounced in exhausted cloves
6 Cloves Coated with mineral
oil
Cloves coated with mineral oil gives kerosene like smell
7 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.
8 Powdered
spices
Added starch Add a few drops of tincture of Iodine or Iodine solution. Indication of blue colour shows the presence of starch. Iodine test for added starch is not applicable for Turmeric powder
9 Powdered
spices
Common Salt Taste for addition of common salt.
10 Turmeric powder
Coloured saw dust Take a tea spoon full of turmeric powder in a test tube. Add 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 not permitted coal tar colour is present. This test is only for Metanil yellow
11 Turmeric whole Lead chromate Appears to be bright in colour which leaves colour immediately in water.
12 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
13 Chillies powder Brick 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.
To a little powder of chilli add small amount  of  conc HCl and mix to the consistency of paste,dip the rear end of the match stick into the paste and hold over the flame,brick red flame colour due to the presence of calcium slats in brick powder.
This test is only for earthy material
14 Artificial colours Sprinkle the chilli powder on a glass of water. Artificial colorants descend as coloured streaks.
15 Water soluble coal tar colour

Water soluble artificial color 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

16 Asafoetida
(Hing)
Soap stone or other
earthy material
Shake little portion of the sample with water and allow to settle.Soap stone or other earthy mailer will settle down at the bottom. In compounded asafoetida due to presence of starch, a slight turbid solution may be produced.However, this will settle down after keeping
17 Starch Add tincture of iodine, appearance of blue colour shows the presence of starch. Compound of asafoetida
contains starch  which is
declared on the label. This test is not applicable for
compound asafoetida.
18 Foreign resin Burn on a spoon, if the sample burns like camphor, it indicates the sample is pure. Pure hing burns like aromatic camphor
19 Spices Powdered bran and saw dust Sprinkle on water surface. Powdered  
bran and sawdust float on the surface.
20 Cinnamon Cassia bark Cinnamon barks are very thin and can be rolled. It can be rolled around a pencil or pen. It has a distinct  smell. Whereas cassia ark comprise of several layers  in between the rough outer and inner most smooth layers. On examination of the ark loosely, a clear distinction can be made.
21 Cumin seeds Grass  seeds  coloured 
with charcoal dust
Rub the cumin seeds on palms. If palms turn black adulteration is indicated.
22 Green chilli and 
green vegetables
Malachite green Take a cotton piece soaked in liquid paraffin and rub the outer green surface of a small part of green  vegetable. If the cotton turns, green, we can say   the vegetable is adulterated with malachite green.
23 Green peas Artificially coloured Take a little amount of green peas in a 250 ml beaker add water to it and mix well. Let it stand for half an  hour. Clear separation of colour in water indicates  adulteration.
24 Saffron Dried tendrils of 
maizecob
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

Miscellaneous Products

S.No Food Article Adulterant Method for Detection Remarks
1 Common salt White powdered 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.
2 Iodized salt Common salt Cut a piece of potato, add salt and wait minute  and  add two drops of lemon juice. If iodized salt blue  colour will develop. In case of common salt, there will be no blue colour.
3 Tea leaves Exhausted tea 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 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.
4 Iron fillings By moving a magnet through the sample,iron filling can be separated.
5 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
6 Supari Pan
Masala
Colour Colour dissolves in water
7 Saccharin Saccharin gives excessive and lingering sweet taste and leaves bitter taste at the end.
8 Catachu powder Chalk Chalk  gives  effervescence  (gives off  bubbles) with concentrated Hydrochloric acid This test is only
for Chalk.
9 Lemonade soda Mineral acid Pour 2 drops of the lemonade soda on a metanil yellow    paper - strip.  A violet colouration indicates the presence    of mineral acid in aerated water. The colour impression  gets retained even after drying the paper (you  can  prepare metanil yellow paper strips by soaking filter paper strips in 0.1 % aqueous solution and then drying the paper – strips)
10 Sweet Potato Rhodamine B colour Take a cotton piece soaked in liquid paraffin, and rub the  outer red surface of the sweet potato. If the cotton absorb colour, it indicates the use of rhodamine B colours   on the outer surface of the sweet potato.
11 Pulses Lead Chromate Shake 5 gm. Of pulse with 5 ml. Of water and add a few  drops of HCl. Pink colour indicates Lead Chromate.
12 Iodized salt Common salt Cut a piece of potato, add salt and wait minute and add  two drops of lemon juice. If iodized salt blue colour will  
develop. In case of common salt, there will be no blue colour.
13 Silver leaves Aluminium leaves (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 aluminium leaves in palm and rub between both the palms of the hand, silver leaves completely disappear in the hand; however presence of small  ball in the palm indicates adulteration with aluminium leaves.
14 Vinegar Mineral Acid Test with the Metanil yellow indicator paper, in case, the colour changes from yellow to pink,mineral acid is present

Source : Quick Test For some Adulterants In Food- Instruction Manual by FSSAI

3.19749216301
Ashish Sep 27, 2019 01:58 PM

This information is very helpful for coman public

RAMBO Sep 04, 2019 07:30 PM

Very helpful for gaining information

10v Aug 05, 2019 11:24 PM

Thanks alot
Helped me alot

KUNAL Jun 28, 2019 04:05 PM

THANKS A LOT!

kunal Jun 28, 2019 02:27 PM

thanks a lot!

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