Adulterant

Method of detection

Water

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.

Starch

Add a few drops of tincture of Iodine or Iodine solution. Formation of blue colour indicates the presence of starch.

Urea

Take a teaspoon of milk in a test tube. Add half 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 half a minute. A change in colour from red to blue indicates the presence of urea in the milk.

Detergent

Shake 5-10 ml of sample with an equal amount of water. Lather indicates the presence of detergent

Synthetic milk

Synthetic milk has bitter after taste, gives a soapy feeling on rubbing between the fingers and turns  yellowish on heating

Synthetic milk - test for protein

The milk can be easily tested using Urease strips. Colour chart in Urease strips helps to arrive at the quantity of urea present in the milk.

Test for Glucose /Invert sugar

Take a strip of Diacetric strip and dip into the milk for 30 sec to 1 min. If the strip changes the colour then it shows the sample of milk contains glucose. If there is no change in the colour of the strip, then glucose is absent

Adulterant

Method of detection

Vanaspati

Take 3 ml of milk in a test tube. Add 10 drops of Hydrochloric Acid. Mix one teaspoonful of sugar. After 5 minutes, examine the mixture. The red colouration indicates the presence of vanaspati in the milk

formalin

Take 10ml of milk in a test tube and add 5 ml of concentrated Sulphuric acid from the sides of the wall without shaking. If a violet or blue ring appears it shows the presence of formalin.

Ammonium Sulphate

•Take 5 ml of hot milk in a test tube. Add a suitable acid, eg., 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. The appearance of a precipitate indicates the presence of Ammonium Sulphate.
• Take 5 ml of milk in a test tube. Add 2.5 ml of 2% Sodium Hydroxide, 2.5 ml of 2% Sodium Hypochlorite and 2.5 ml of 5% Phenol Solution. Heat for 20 seconds in boiling water bath. If the bluish colour turns to deep blue, it indicates the presence of Ammonium Sulphate. However, in case it turns pink, it shows that the sample is free from Ammonium Sulphate.

Hydrogen Peroxide

• 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,
Or
• To 10 ml of milk sample in a test tube add 10-15 drops of Vanadium Pentoxide reagent and mix. Pink or red colour indicates the presence of Hydrogen Peroxide.

Sugar

Take 3 ml of milk in a test tube. Add 2 ml of the hydrochloric acid. Heat the test tube after adding 50 mg of resorcinol, The red colouration indicates the use of sugar in the milk.

Sodium bi-carobonate / Neutralizer

Take 3 ml of milk in a test tube and add 5 ml of rectified spirit to it. Then add 4 drops of rosalic acid solution. The appearance of red/rosy colouration indicates the presence of Sodium bicarbonate in the milk.

Boric acid

Take 3 ml of milk in a 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 one drop of ammonia solution, indicates that the boric acid is present in milk

Removal of Fat

The Lactometer reading will go above 26