Milk is considered as one of the best sources of nutrition but at the same time it is one of the most affected food products with the use of adulterants. Milk Adulteration is done through various means and posing serious threat to human health especially for infants & young children, because the average milk intake is relatively higher in them.
The FSS Act has provisions for the penalty & prosecution but still the offenders of Milk Adulteration are active in many parts of India. The Supreme Court of India has recently asked the Central Govt to make the norms more stringent to punish the wrong doers.
The Food Safety and Standards Authority of India has recently shared a document through which some of the common adulterants could be analyzed in the laboratories.
To check if Vanaspati is added in Milk – Take 3 ml of milk in a test tube and add 10 drops of Hydrochloric Acid, then mix one teaspoonful of sugar in it. After 5 mins, examine the mixture. The Red coloration would indicate the presence of Vanaspati in the Milk.
To check if Formalin is added in Milk – Take 10 ml 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 at the intersection of two layers then it shows presence of formalin. Formalin is being used as a preservative in the milk.
To check if Ammonium Sulphate is added in Milk – 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% Bariun Chloride. Appearance of precipitate indicates the presence of Ammonium Sulphate.
Take 5 ml of milk in test tube. Add 2.5 ml of 2% of 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 bluish color 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.
Ammonium Sulphate is used to increase the lactometer reading.
To check if Salt is added in Milk – Take 5 ml of Silver Nitrate reagent in a test tube. Add 2-3 drops of potassium Dichromate Reagent. Add 1 ml of Milk in the above test tube and mix thoroughly. If the contents of the test tube turn Yellow, the milk contains Salt. It it turns to Chocolate color or Reddish Brown, the milk sample is free from salt.
Addition of Salt in milk is mainly resorted to with the aim of increasing the corrected lactometer reading.
To check if Hydrogen Peroxide is added in Milk – Take 5 ml milk in a test tube. Add 3 drops of Paraphenylene Diamine and shake well. Change in color of the milk to Blue confirms that the milk is adulterated with Hydrogen Peroxide.
Take 10 ml milk sample in a test tube add 10-15 drops of Vanadium Pentoxide reagent and mix. Pink or Red color indicates presence of Hydrogen Peroxide.
To check if Sugar is added in Milk – 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 coloration indicates the use of sugar in the milk.
To check if Sodium bi-carbonate/neutralizer is present in Milk – Take 3 ml of milk in a test tube and add 5 ml of rectified spirit to it, then add 4 drops of Rosolic Acid solution. The appearance of Red/Rosy coloration indicates the presence of sodium bi-carbonate in the milk.
To check if Boric Acid is added in Milk – 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 color 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 the milk. To prepare the Yellow paper strip, dip strips of filter paper in an aqueous solution of the turmeric and dry it up.
To check if Fat has been removed from the Milk – The reading on the Lactometer will show above 26 but still the milk will apparently remain thick.