24 June 2012

Check Your Food

Simple Screening test for Detecting Adulteration in Common Food :

Vegetable oil
Castor oil
Take 1 ml. of oil in a clean dry test tube. Add 10 ml. Of acidified petroleum ether. Shake vigorously for 2 minutes. Add 1 drop of Ammonium Molybdate reagent. The formation of turbidity indicates presence of Castor oil in the sample.

Argemone oil
Add 5 ml, conc. HNO3 ­­to 5 ml.sample. Shake carefully. Allow to separate yellow, orange yellow, crimson colour in the lower acid layer indicates adulteration.
Mashed Potato
Sweet Potato, etc.
Boil 5 ml. Of the sample in a test tube. Cool and a drop of iodine solution. Blue colour indicates presence of Starch.  colour disappears on boiling &  reappears on cooling.

Take 5 ml. Of the sample in a test tube. Add 5 ml. Of Hydrochloric acid and 0.4 ml of 2% furfural solution or sugar crystals. Insert the glass stopper and shake for 2 minutes. Development of a pink or red colour indicates presence of Vanaspati in Ghee.

Rancid stuff (old ghee)
Take one teaspoon of melted sample and 5 ml. Of HCl in a stoppered glass tube. Shake vigorously for 30 seconds. Add 5 ml. Of 0.1% of ether solution of Phloroglucinol. Restopper & shake for 30 seconds and allow to stand for 10 minutes. A pink or red colour in the lower(acid layer) indicates rancidity.

Synthetic Colouring Matter
Pour 2 gms. Of filtered fat dissolved in ether. Divide into 2 portions. Add 1 ml. Of HCl to one tube. Add 1 ml. Of 10% NaOH to the other tube. Shake well and allow to stand. Presence of pink colour in acidic solution or yellow colour in alkaline solution indicates added colouring matter.
Invert sugar/jaggery
1.      Fiehe’s Test: Add 5 ml. Of solvent ether to 5 ml. Of honey. Shake well and decant the ether layer in a petri dish. Evaporate completely by blowing the ether layer. Add 2 to 3 ml. Of resorcinol (1 gm. Of resorcinol resublimed in 5 ml. Of conc. HCl.) Appearance of cherry red colour indicates presence of sugar/jaggery.

2.      Aniline Chloride Test : Take 5 ml. Of honey in a porcelain dish. Add Aniline Chloride solution (3 ml of  Aniline and 7 ml. Of 1:3 HCl) and stir well. Orange red colour indicates presence of sugar.

Kesari dal(Lathyrus sativus)
Add 50 ml. Of dil.HCl to a small quantity of dal and keep on simmering water for about 15 minutes. The pink colour, if developed indicates the presence of Kesari dal.
Metanil Yellow(dye)
Add conc.HCl to a small quantity of dal in a little amount of water. Immediate development of pink colour indicates the presence of metanil yellow and similar colour dyes.

Lead Chromate
Shake 5 gm. Of pulse with 5 ml. Of water and add a few drops of HCl. Pink colour indicates Lead Chromate.
Ergot infested Bajra
Swollen and black Ergot infested grains will turn light in weight and will float also in water
Wheat flour
Excessive sand & dirt
Shake a little quantity of sample with about 10 ml. Of Carbon tetra chloride and allow to stand. Grit and sandy matter will collect at the bottom.

Excessive bran
Sprinkle on water surface. Bran will float on the surface.

Chalk powder
Shake sample with dil.HCl Effervescence indicates chalk.
Common spices like Turmeric, chilly, curry powder,etc.
Extract the sample with Petroleum ether and add 13N H2SO4 to the extract. Appearance of red colour (which persists even upon adding  little distilled water) indicates the presence of added colours. However, if the colour disappears upon adding distilled water the sample is not adulterated.
Black Pepper
Papaya seeds/light berries, etc.
Pour the seeds in a beaker containing Carbon tetra-chloride. Black papaya seeds float on the top while the pure black pepper seeds settle down.
Powdered bran and saw dust
Sprinkle on water surface. Powdered bran and sawdust float on the surface.
Coriander powder
Dung powder
Soak in water. Dung will float and can be easily detected by its foul smell.

Common salt
To 5 ml. Of sample add a few drops of silver nitrate. White precipitate indicates adulteration.
Brick powder grit, sand, dirt, filth, etc.
Pour the sample in a beaker containing a mixture of chloroform and carbon tetrachloride. Brick powder and grit will settle at the bottom.
Badi Elaichi seeds

Choti Elaichi seeds

Separate out the seeds by physical examination. The seeds of Badi Elaichi have nearly plain surface without wrinkles or streaks while seeds of cardamom have pitted or wrinkled ends.
Turmeric Powder
Starch of maize, wheat, tapioca, rice
A microscopic study reveals that only pure turmeric is yellow coloured, big in size and has an angular structure. While foreign/added starches are colourless and small in size as compared to pure turmeric starch.
Lead Chromate
Ash the sample. Dissolve it in 1:7 Sulphuric acid (H2SO4) and filter. Add 1 or 2 drops of 0.1% dipenylcarbazide. A pink colour indicates presence of Lead Chromate.

Metanil Yellow
Add few drops of conc.Hydrochloric acid (HCl) to sample. Instant appearance of violet colour, which disappears on dilution with water, indicates pure turmeric. If colour persists Metanil yellow is present.
Cumin seeds
(Black jeera)
Grass seeds coloured with charcoal dust
Rub the cumin seeds on palms. If palms turn black adulteration in indicated.
Soap stone, other earthy matter
Shake a little quantity of powdered sample with water. Soap stone or other earthy matter will settle at the bottom.

Shake sample with Carbon tetrachloride (CCl4). Asafoetida will settle down. Decant the top layer and add dil.HCl to the residue. Effervescence shows presence of  chalk.
Food grains
Hidden insect infestation
Take a filter paper impregnated with Ninhydrin (1% in alcohol.) Put some grains on it and then fold the filter paper and crush the grains with hammer. Spots of bluish purple colour indicate presence of hidden insects infestation


Put a drop of milk on polished vertical 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.
Take 5 ml of milk in a test tube and add 2 drops of bromothymol blue soln. Development of blue colour after 10 minutes indicates presence of urea.
Ice Cream
Washing Powder
Put some lemon juice, bubbles are observed on the presence of washing powder
Dissolve sugar in a glass of water, chalk will settle down at the bottom, similarly for salt
Silver Foil
Aluminum Foil
On ignition genuine silver foil burns away completely leaving glistening white spherical ball of the same mass while aluminum foil is reduced to ashes of black Grey colour.
Gently sprinkle the coffee powder on surface of water in a glass.  The coffee floats over the water but chicory begins to sink down within few seconds.  The falling chicory powder particles leave behind them a trail of colour, due to large amount of caramel they contain
Coloured leaves

 Used tea

Iron fillings
Rub leaves on white paper, artificial colour comes out on paper.
Tea leaves sprinkled on wet filter paper. Pink or red spots on paper show colour
Move a magnet through the sample. Iron will stick to the magnet.
Red Chilli powder
Rodemine Culture

Brick Powder
Take 2gms sample in a test tube, add 5ml of acetone. Immediate appearance of red colour indicates presence. of Rodamine
 Brick powder settles fast chilli powder settles slowly when put in water.
Coloured dried tendrils of maize cob
Pure saffron will not break easily like artificial. Pure saffron when allowed to dissolved in water will continue to give its colour so long as it lasts.

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