Adulteration of Food-Meaning,Adulteration in Milk and Pulses

Adulteration of Food

“Adulterant” means any material which is or could be employed for making the food unsafe or sub-standard or misbranded or containing extraneous matter.
Food Adulteration is an act of intentionally debasing the quality of food offered for sale either by the admixture or substitution of inferior substances or by the removal of some valuable ingredient.
Food is declared adulterated if :

  • A substance is added which depreciates or injuriously affects it.
  • Cheaper or inferior substances are substituted wholly or in part.
  • Any valuable or necessary constituent has been wholly or in part abstracted.
  • It is an imitation.
  • It is coloured or otherwise treated to improve its appearance or if it contains any added substance injurious to health.
  • For whatever reasons its quality is below the Standard.

Adulterated food is dangerous because it may be toxic and can affect health and it could deprive nutrients essential for proper growth and development.
Adulteration in Milk
The list of common adulterants and their method of detection is given below:

  1. Water

         Method of Detection:

  • The presence of water can be detected by putting a drop of milk on a polished slanting surface. The drop of pure milk flows slowly leaving a white trail behind it whereas milk adulterated with water will flow immediately without leaving a mark.
  1. Starch

Method of detection

  • Add a few drops of 1% Iodine solution. Formation of blue colour indicates the presence of starch.
  1. Urea

Urea is generally added in the preparation of synthetic milk to raise the SNF (Solid not Fat) value.
          Method of Detection

  • Five ml of milk is mixed well with 5 ml paradimethyl amino benzaldehyde (16%). If the solution turns yellow in colour, then the given sample of milk is added with urea.
  • Take 5 ml of milk in a test tube and add 0.2 ml of urease (20 mg / ml). Shake well at room temperature and then add 0.1 ml of bromothymol blue solution (0.5%). Appearance of blue colour after 10-15 min indicates the adulteration of milk with urea.
  1. Vanaspati

          Method of detection

  • 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.
  1. Formalin

Formalin (40%) is poisonous though it can preserve milk for a long time.
         Method of detection

  • Take 10 ml of milk in test tube and 5 ml of conc. sulphuric acid is added on the sides of the test tube with out shaking. If a violet or blue ring appears at the intersection of the two layers, then it shows the presence of formalin.
  1. Glucose

Usually poor quality glucose is added to milk to increase the lactometer reading. There are    two tests available to detect the adulteration of milk with glucose.
         Method of Detection

  • Phosphomolybdic or Barford Test

Take 3 ml of milk in a test tube and add 3 ml Barford’s reagent and mix it thoroughly. Then keep it in a boiling water bath for 3 min and then cool it for 2 min by immersing in tap water with out disturbance. Then add 1 ml of phosphomolybdic acid and shake. If blue colour is visible, then glucose is present in the milk sample.

  • Diacetic test

Take a strip of diacetic strip and dip it in the milk for 30 sec to 1 min. If the strip changes colour, then it shows that the sample of milk contains glucose. If there is no change in the colour of the strip, then glucose is absent. In this method the presence of glucose in milk can be quantified by comparing the colour developed with the chart strip.

  1. Skim milk powder in milk

            Method of Detection

  • If the addition of nitric acid drop by drop in to the test milk sample results in the development of orange colour, it indicates the milk is adulterated with skim milk powder. Samples with out skim milk powder shows yellow colour.
  1. Buffalo milk in cow milk

          Method of Detection

  • The presence of buffalo milk in cow milk is tested by Hansa test. It is based on immunological assay. One ml of milk is diluted with 4 ml of water and then it is treated with 1 ml of antiserum. The characteristic precipitation reaction indicates the presence of buffalo milk in the sample taken. (The antiserum is developed by injecting buffalo milk proteins into rabbits).
  1. Ammonium Sulphate

  Method of Detection

  • Take 5 mli of hot milk in a test tube. Add a suitable acid, e.g. Citric acid. The whey obtained is separated and filtered. Take the whey in another test tube and add 0.5 ml of 5% Barium Chloride. Appearance of precipitate indicates the presence of Ammonium Sulphate.
  • Take 5 ml of milk in a test tube. Add 2.5 ml of 2% Sodium Hypochlorite and 2.5 ml of 5% Phenol Solution. Heat for 20 seconds in boiling water bath. If blish colour turns to deep blue, it indicated the presence of Ammonium Sulphate. However in case it turns pink, it shows that the sample is free from Ammonium Sulphate.


  1. Hydrogen peroxide

           Method of detection

  • Take 5 ml milk in a test tube. Add 3 drops of Paraphenylene Diamine and shake well. Change in colour of the milk to blue confirms that the milk is adulterated with Hydrogen peroxide.
  • To 10ml of  milk sample in a test tube add 10-15 drops of  vanadium pentoxide reagent and mix. Pink or red colour indicates presence of Hydrogen peroxide.


  1. Boric acid

          Method of Detection

  • Take 3 ml of milk in test tube. Add 20 drops of hydrochloric acid and shake the test tube or mix up the contents thoroughly. Dip a yellow paper strip and remove the same after 1 minute. A change in colour from yellow to red, followed by the change from red to green by addition of once drop of ammonia solution indicates that the boric acid is present in milk.

Milk is most commonly diluted with water. This  reduces its nutritional value and contaminated water can also cause additional health problems.The other adulterants used are mainly starch, sodium hydroxide (caustic soda), sugar, urea, hydrated lime, sodium carbonate, formalin, and ammonium sulphate.
The Indian Council of Medical Research has reported that “milk adulterants have hazardous health effects. The detergent in milk can cause food poisoning and other gastrointestinal complications. Its high alkaline level can also damage body tissue and destroy proteins. Other synthetic components can cause impairments, heart problems, cancer or even death. While the immediate effect of drinking milk adulterated with urea, caustic soda and formalin is gastroenteritis, the long-term effects are far more serious.”
Adulteration in Pulses
One of the greatest sources of protein, fiber, and nutrition is pulses. Adding pulses to  everyday diet keeps us healthy. They are good for the heart and help manage diabetes and coeliac disease. But, addition of adulterants is common these days. These  adulterants reduce the quality of pulses, giving naissance to curable and incurable diseases when consumed regularly.
Common adulterants in pulses

  • Sand, marble chips, stones, these adulterants affect the digestive tract.
  • Lathyrus sativus is mixed with khesari dal or other pulses
  • Asbestos in particulate or powder form (for polishing); it causes cancer
  • Metanil yellow is added to old stocks of pulses to enhance color; it is carcinogenic and causes stomach disorders. It also causes testicular degeneration in the male if consumed for long
  • Soluble coal tar dye is used to enhance quality and make the pulses look clean; it is highly injurious to health.
  • Khesari dal stones are often mixed with other pulses. Continuous consumption of this dal cause paralysis of the limbs.

Method of detection
The addition of extraneous matter like grains stone, marble chips and other filth to grain is also widely practised, specially in times of scarcity. These can be separated by visual inspection. In order to detect Metanil Soak the pulses in light warmed water. After sometimes, mix a few drops of hydrochloric acid into it. If after a while, a light pink colour would be noticeable indicating the presence of the metanil yellow .

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