Milk Adulteration - Effects, Common Adulterants & How to Check

The milk industry is growing at a rapid pace in India, with nearly 2 lakh villages involved in the dairy industry. Additionally, India is globally the largest exporter of milk, but there is a huge gap between production and consumption. Traders highly overcome this gap with milk adulteration.

Wondering what milk adulteration is? Read along!

Food adulteration refers to the act of intentionally degrading the quality of food used for sale either by mixing or substituting with low-quality substances or by removing essential ingredients. The same is applicable for milk.

Food adulteration also includes contamination during harvesting, growth, processing, transportation and distribution. However, there is a difference between milk contamination and adulteration, which is discussed in the following section.

As per this definition, milk adulteration refers to the act of wilfully debasing the quality of milk as well as increasing quantity to make a profit illegally.

Milk is considered adulterated in any of the following cases -

• An addition of substances that may affect health
• Removal of an essential nutrient wholly or partially
• Addition of inferior substances to substitute nutrients wholly or partly
• Other reasons which may lower the quality below the standard level

Milk is a prime source of protein, calcium, vitamin D, vitamin A and other essential nutrients. Individuals whose diet includes dairy products have lower chances of cardiovascular diseases, high blood pressure, and type 2 diabetes. Milk is further necessary to improve bone health. Hence, it is imperative to ensure both children and adults drink pure milk.

However, the growing rate of milk adulteration in India to increase profit has burdened people with doubt and concerns. The collection and testing of milk across India have failed to conform to the standards set by the Food Safety and Standards Authority of India (FSSAI).

The demand for milk is always high, which further multiplies during festivals in India. Due to this high demand, merchants often fail to bridge the gap between demand and supply using pure milk. 

Hence, they opt for the process of milk adulteration to supply more milk by degrading the quality but keeping the profit intact.    

Here is a list of the harmful effects of adulterated milk and contaminated milk.

• Kidney issues
• Heart-related issues
• Organ malfunctioning
• Low vision
• Cancer
• Death

The World Health Organisation suspects that a huge population in India might suffer from life-threatening diseases by 2025.

Here, one must note that the severity of harmful effects depends on the adulterants used in milk contamination and milk adulteration.

Note: Adulterants comprise those harmful or low-quality materials, which make something inferior or less pure or unsafe.

Below is a list of usage of common adulterants in milk and their effects on health.

• Melamine and urea can cause kidney-related problems.
• Formalin (used to increase milk’s shelf life) can cause skin problems and cancer.
• Detergents can cause intestine and kidney issues.
• Starch can cause diarrhoea. Further, if an excessive amount of starch deposits in the body, it can lead to diabetes.
• Hydrogen peroxide can harm the digestive system.
• Oxytocin injection (hormone injected to cows and buffaloes to increase milk production) can cause issues in the kidney, heart, eye, etc.

Individuals, who are worried about consuming impure or low-quality milk, can conduct an adulteration test for milk at home.

Read on to know about how to test milk purity at home.

Following is a list of tests that individuals can conduct at home to check for impurities in milk -

Test to Check the Presence of Water in Milk

To conduct this test, individuals have to put a drop of milk at any slanted surface. If the milk flows quickly, it proves that it contains water as pure milk will flow slowly, leaving a trace behind. Adulterated milk will certainly not leave a mark behind.

Test to Check the Presence of Starch in Milk

To check whether milk contains starch or not, individuals have to boil 2-3 ml of milk with 5 ml of water. Next, they have to add 2-3 drops of tincture of iodine once the milk and water mixture cools down. If the addition of iodine results in blue colour formation, then the sample milk undoubtedly contains starch.

Test to Check the Presence of Urea in Milk

Urea is a common adulterant which merchants use to make it impure. The presence of urea in milk does not change its taste and is hard to detect. Therefore, to find out if your daily supply of milk contains urea, individuals have to mix a tablespoon of milk and soybean powder and shake well. Next, they have to dip a litmus paper for a few seconds. If the colour changes from red to blue, the sample has urea in it.

Test to Check the Presence of Detergent in Milk

Detergents are highly used for milk adulteration. To check the presence of detergent in milk at home, individuals have to take 5-10 ml of milk and an equal quantity of water and shake it well. If they see that that milk-water mixture forms a dense lather, it suggests adulteration in milk. Pure milk forms a thin layer of foam.

Test for Synthetic Milk

Individuals can easily detect synthetic milk by sniffing it. Synthetic milk has a bad taste and odour. Further, they can perceive a soapy smell and feel soapy when rubbing it with their hands. The presence of chemicals leads to these conditions.

Apart from trying these tests at home, individuals can rely on lab testing - the methods used in lab testing are discussed in the following section.

The following methods are commonly used in the laboratory for detecting adulterants in milk. Take a look.

Test for Detection of Vanaspati

Lab technicians have to pour 3 ml milk, 10 drops of hydrochloric acid and 1 tablespoon of sugar inside a test tube. Next, they have to rest the mixture for 5 minutes and examine the change of colouration. If the mixture turns red, it means the milk contains vanaspati.

Test for Detection of Formalin

Here, lab technicians will have to take a test tube and add 10 ml milk. Then, they have to slowly pour concentrated formalin(5 ml) from the side of the test tube wall. They have to pour the acid very carefully without shaking it. If the mixture forms a red or violet ring at the meeting point of two layers, it points to the existence of formalin in it.

Test for Detection of Hydrogen Peroxide

While conducting a milk adulteration lab test to particularly detect hydrogen peroxide, lab technicians will take a test tube and pour 5 ml of silver nitrate reagent,3 drops of Paraphenylene Diamine. Next, they will shake the mixture thoroughly. If the colour changes to blue, then the milk contains hydrogen peroxide.

Alternatively, they can try different methods and combinations. Here, they can pour 10 ml of milk into a test tube and add vanadium pentoxide reagent measuring 10-15 drops. After mixing, if the colour changes to pink or red, hydrogen peroxide is present in milk.

Test for Detection of Salt

Lab technicians will take 5 ml of silver nitrate reagent in a test tube to detect salt in milk. Next, they will pour 2 to 3 drops of potassium dichromate reagent. After that, they will again pour 1 ml of milk and mix it well. If the mixture turns yellow, it indicates that salt is present.

Test for Detection of Boric Acid

To check whether milk contains boric acid or not, lab technicians will take 3 ml of milk in a test tube and add 20 drops of hydrochloric acid. After that, they will shake the mixture well. Next, they will dip a paper strip of yellow colour and leave it for 1 minute. If the mixture turns from red to yellow and red to green (after adding 1 drop of ammonia solution), it points to the presence of boric acid in milk.

Test for Detection of Ammonium Sulphate

To complete the lab testing of adulterated milk, lab technicians have to take a test tube and pour hot milk (5 ml) and citric acid. Next, they will separate the whey that has formed and filter it. After that, they have to put the whey in a separate test tube and add 0.5 ml of 5% barium chloride. If precipitate appears in the test tube, it indicates the existence of ammonium sulphate.

Here is the laboratory method for checking adulteration in milk, particularly for ammonium sulphate. Lab technicians will have to take a test tube and pour 5 ml milk, 2.5 ml of 2% sodium hypochlorite, 2.5 ml of 2% phenol solution, and 2.5 ml of 2% sodium hydroxide. Next, they have to heat the mixture for 20 seconds in a boiling water bath. If the bluish colour of the mixture turns deep blue, then the mixture contains Ammonium Sulphate.