Simple Tests For Food Adluterants

Food Standard and Quality Control

Lesson 24 : Food Adulteration

Simple Tests For Food Adluterants

  1. Ghee or Butter

    Adulterants- Vanaspathi
    Identification test:

    1. Take about one teaspoonful of melted ghee or butter with equal quantity of concentrated Hydrochloric Acid in a test tube and add to it a pinch of cane sugar. Shake well for one minute and test it after 5 minutes.
    2. Appearance of crimson colour in lower (acidic) layer shows the presence of ‘vanaspathi'. This test is specific for seasame oil which is compulsorily added to vanaspathi. Some of coaltar dyes also give a positive test.

    Adulterants - Mashed potatoes, sweet potato and other starches
    Identification test:

    • Add a drop of tincture of iodine. Iodine which is brownish in colour turns to blue if mashed potatoes/sweet potatoes/other starches are present.
  2. Milk

    Adulterants- Water

    1. The lactometer reading should not ordinarily be less than 1.026.
    2. The presence of water can be detected by putting a drop of milk on a polished vertical surface. The drop of-pure milk either stops or flows slowly leaving a while trail behind it; whereas milk adulterated with water will flow immediately without leaving a mark.
    3. Add tincture of iodine, indication of blue colour shows the presence of starch.
  3. Adulterants- Starch

    • This test is not valid if skimmed milk or other thickening material is added.
  4. khoa

    Adulterants- Starch
    Add tincture of iodine. Indication of blue colour shows the presence of starch.

  5. Edible oils

    Adulterants- Argemone oil
    Add concentrated nitric acid to a sample and shake carefully. Red to reddish brown colour in acid layer would indicate the presence of argimone oil.

    Adulterants- Mineral oil
    Take two ml of edible oil and add an equal quantity of N/2 alcoholic potash. Heat in boiling water both for 15 minutes and add 10ml of water. Any turbidity shows the presence of mineral oil.

    Adulterants- Castor oil
    Dissolve some oil in petroleum ether in a test tube and cool in ice salt mixture. Presence of turbidity within 5 minutes indicates the presence of oil.
    • This test is not for minute traces.

  6. Sweet meat, Ice cream, Sherbet

    Adulterants- Metanil yellow (a non permitted coal tar dye)
    Extract colour with luke warm water from food article. Add few drops of cone. Hydrochloric Acid. If magenta red colour develops the presence of metanil yellow is indicated.

  7. Dhals

    Adulterants- Kesari dhal
    Add 50 ml of dilute Hydrochloric acid to dhal and keep on simmering water for about 15 minutes. The pink colour if developed indicates the presence of kesari dhal.

    Adulterants- Clay, stones, gravels lead chromate
    Visual examination will detect these adulterants.
    Shake five grams of dhal with five ml of water and add a few drops (yellow) of Hydrochloric Acid. A pink colour shows the presence of colour.

  8. Hing

    Adulterants-Soap stone (pumice stone) or other earthy matter
    Shake with water, soap stone or other earthy matter will settle to the bottom.
    Same tests as in the case of milk.

  9. Tea leaves

    Adulterants- Exhausted tea or black
    Tea leaves sprinkled on wet filter paper would immediately release added colour.

    Adulterants-Bengal gram dal husk with colour.
    Spread a little slaked lime on white porcelain tile or glass plate. Sprinkle a little tea dust on the lime will show the presence of coal tar dye. In the case of genuine tea, there will be only a slight greenish yellow colour due to chlorophyll which appears after sometime.

  10. Saffron

    Adulterants- Dyed 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 dye. The colour dissolves in water if artificially coloured. A bit of pure saffron when allowed to dissolve in water will continue to give its' saffron colour so long as it lasts.

  11. Wheat, bajra and other food grainsAdulterants-Ergot (a fungus containing a poisonous substance)
    1. Purple black longer size grains in bajra show the presence of ergots.
    2. Put some grains in a glass containing 20%salt solution. Ergot floats over the surface while sound grains settle down.

    Adulterants- Dhatura-seeds
    Dhatura seeds resemble chilly seeds with blackish brown colour which can be separated out by close examination.

  12. Sugar

    Adulterants- Chalk powder
    Dissolve in a glass of water, chalk will settle down at the bottom.

  13. Black Pepper

    Adulterants- Dried seeds of papaya fruit
    Papaya seeds can be separated out from pepper as they are shrunken, oval in shape and greenish 'brown or brownish black in colour. The suspected papaya seed in black pepper sample is distinguishable by its characteristic repulsive flavour quite distinct from the bite of black pepper.

    Adulterants- Light Berries
    Light Berries float on spirit

  14. Silver Leaves

    Adulterants- Aluminium leaves
    On ignition genuine silver leaves burn away completely, leaving glistening white spherical ball of the same mass whereas aluminium leaves are reduced to ashes of dark grey blackish colour. The silver foil is very thin and if crushed between two fingers, crumbles to powder. Aluminium foil is comparatively thicker and only breaks to small shreds when crushed similarly.

  15. Turmeric

    Adulterants- Coloured saw dust. Metanil yellow.
    Take a teaspoon full of turmeric powder in a test tube. Add a few drops of conc. Hydrochloric Acid. Instant appearance of violet colour which disappears on dilution with water. If the colour persists metanil yellow (an artificial dye) non permitted coal tar dye is indicated.
    • This test is only for metanil yellow.

  16. Chilli powder

    Adulterants- Stones
    Any grittiness that may be felt on tapping the sediment at the bottom of glass confirms the presence of brick powder or sand. Smooth white residue at the bottom indicates the presence of soapstone.

    Adulterants- Artificial colour
    Water soluble artificial dye can be detected by sprinkling a small quantity of chilli or turmeric powder on the surface of water contained in a glass tumbler. The soluble dye will immediately start descending in colour streaks.

  17. Jaggery powder

    Adulterants- Chalk powder

    1. Add few drops of HCl, Effervescence indicates adulteration
    2. Stir a spoonful sample of sugar in a glass of water. The chalk settles down.
  18. Cloves

    Adulterants- Volatile oil extracted cloves
    Exhausted cloves can be identified by its small size and shrunken appearance. The characteristics pungent taste of genuine cloves is less pronounced in exhausted cloves.

  19. Rawa

    Adulterants- Iron filings
    By moving a magnet through it iron filings can be separated.

  20. Rice

    Adulterants- Marble or other stones
    A simple test is to place a small quantity of rice on the palm of the hand and gradually immerse the same in water. The stone chips will sink.

  21. Wheat flour(maida)

    Adulterants-Atta from which maida suji has been extracted
    When dough is prepared from resultant wheat flour, more water has to be used and chapaties prepared out of this will blowout. The normal taste of chapaties prepared out of wheat is some what sweetish whereas those prepared out of adulterated wheat flour will taste insipid.

  22. Common salt

    Adulterants- White powdered stone, chalk
    Stir a spoonful of simple salt in a glass of water. The presence of chalk will make the solution white and other insoluble impurities will settle down.

  23. Mustard

    Adulterants- Argemone seeds
    Mustard seeds have a smooth surface. The argemone seed have grainy and rough surface and are blacker hence can be separated out by close examination.

  24. Honey

    Adulterants- Molasses (sugar and water)
    A cotton wick dipped in pure honey when lighted with a match stick burns. If adulterated the presence of water will not allow the honey to burn. If it does it will produce a crackling sound.

  25. Supari

    Adulterants- Colour and saccharin
    Colour dissolves in water. Saccharin gives excessive and lingering sweet taste.

  26. Pulses(green peas)

    Adulterants- Colour dye stuffs and dhals
    Sample is kept immersed in water for about half an hour and stirred. Colour separation indicates adulteration.

  27. Cinnamon

    Adulterants- Cassia bark
    Cinnamon barks are very thin. Cassia barks are thick and stiff, Cinnamon barks can be rolled.

  28. Coffee

    Adulterants- 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 they contain.

    Adulterants- Tamarind or date-seed powder
    Sprinkle the suspected coffee powder on white blotting paper and spray over it 1 % sodium carbonate solution. Tamarind and date-seed powder will, if present, stain blotting paper red.

Last modified: Tuesday, 21 February 2012, 9:43 AM