Tests to Detect Adulteration of Milk

There are lots of methods noted for detection of adulteration in milk however the methods discussed here are simple but rapid and sensitive techniques to detect adulteration.

I. Detection of Neutralizers in milk

1) Rosalic acid test (Soda Test)

In milk neutralizers like hydrated lime, sodium hydroxide, sodium carbonate or sodium bicarbonate are added which can be prohibited.

How to detect?

Take 5 ml of milk inside a test tube and add 5 ml alcohol then 4-5 drops of rosalic acid. When the colour of milk changes to pinkish red, then its inferred the milk is adulterated with sodium carbonate / sodium bicarbonate and therefore unfit for people to drink.

This test is going to be effective only when the neutralizers can be found in milk. When the added neutralizers are nullified through the developed acidity, than the test is going to be negative. If so, the alkaline condition from the milk for that presence of soda ash needs to be estimated.

How to proceed?

2) Take 20 ml of milk inside a silica crucible and so the water is evaporated and also the contents are burnt inside a muffle furnace. The ash is dispersed in 10 ml sterilized water and it is titrated against decinormal (N/10) hydrochloric acid using phenolphthalein being an indicator. When the titre value exceeds 1.2 ml, then its construed the milk is adulterated with neutralizers.

II. Test for detection of hydrogen peroxide

Take 5 ml milk inside a test tube after which add 5 drops of paraphenylene diamine and shake rid of it. Change from the colour of milk to blue confirms the milk is added with peroxide.

III. Test for detection of formalin

Formalin (40%) is poisonous although it can preserve milk for a long period.

How to detect?

Take 10 ml of milk in test tube and 5 ml of conc. sulphuric acid is added about the sides from the test tube without having shaking. If your violet or blue ring appears in the intersection of these two layers, it shows the existence of formalin.

IV. Test for detection of sugar in milk

Generally sugar is included the milk to improve the solids not fat content of milk i.e. to improve the lactometer reading of milk, that was already diluted with water.

How to detect?

Take 10 ml of milk inside a test tube and add 5 ml of hydrochloric acid together with 0.1 g of resorcinol. Then shake the exam tube well and put the test tube inside a boiling water bath for five min. Appearance of red colour indicates the existence of added sugar in milk.

V. Test for detection of starch

Addition of starch also boosts the SNF content of milk. In addition to the starch, wheat flour, arrowroot, rice flour will also be added.

How to detect?

Take 3 ml milk inside a test tube and boil it thoroughly. Then milk is cooled to room temperature and added with Two to three drops of 1% iodine solution. Change of colour to blue suggests that the milk is adulterated with starch.

You will find more tests to detect different adulterants in milk at MILK ADULTERATION TESTS

The author is really a dairy expert, focusing on the technology and microbiology of dairy foods and holds a doctoral degree in Dairy Science; for more information on milk and milk products please visit her site An expert Dairy Site