Simple screening tests for Adulterantion detection.



          Adulteration in food is normally present in its most crude form, prohibited substances are either added or partly or wholly substituted.  In India normally the contamination/adulteration in food is done either for financial gain or due to carelessness and lack in proper hygienic condition of processing, storing, transportation and marketing. This ultimately results that the consumer is either cheated or often become victim of diseases. Such types of adulteration are quite common in developing countries or backward countries. However, adequate precautions taken by the consumer at the time of purchase of such produce can make him alert to avoid procurement of such food. It is equally important for the consumer to know the common adulterants and their effect on health.


In the following table simple screening tests for detection of adulteration in common foods have been prescribed. These tests give idea of presence of adulteration. However, conformation for these adulterations is normally made through laboratory tests.


Simple Screening test for Detecting Adulteration in Common Food

Sr.No
Food article
Adulteration
Test
1
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.
2
Ghee
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.
Vanaspati
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.
3
Honey
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.
4.
Pulses/Besan
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.
5
Pulses
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.
6
Bajra
Ergot infested Bajra
Swollen and black Ergot infested grains will turn light in weight and will float also in water
7
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.
8
Common spices like Turmeric, chilly, curry powder,etc.
Colour
Extract the sample with Petroleum ether and add 13N H2SO4to 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.
9
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.
10
Spices(Ground)
Powdered bran and saw   dust
Sprinkle on water surface. Powdered bran and sawdust float on the surface.
11
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.
12
Chillies
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.
13
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.
14
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.
15
Turmeric
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.
16
Cumin seeds
(Black jeera)
Grass seeds coloured with charcoal dust
Rub the cumin seeds on palms. If palms turn black adulteration in indicated.
17
Asafoetida(Heeng)
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.
Chalk
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.
18
Foodgrains
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
            Selection of wholesome and non-adulterated food is essential for daily life to make sure that such foods do not cause any health hazard. However, visual examination of the food before purchase makes sure to ensure absence of insects, visual fungus, foreign matters, etc. 
                         Therefore, due care  taken by the consumer at the time of purchase of food after thoroughly examining can be of great help. Secondly, label declaration on packed food is very important for knowing the ingredients and nutritional value . It also helps in checking the freshness of the food and the period of best before use. The consumer should avoid taking food from an unhygienic place and food being prepared under unhygienic conditions.
                         Such types of food may cause various diseases. Consumption of cut fruits being sold in unhygienic conditions should be avoided. It is always better to buy certified food from reputed shop.

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