Adulteration Tests for Milk & Milk Products: How to check purity of milk

Food adulteration has been a matter of great concern for the food safety and standards authority of the India (FSSAI) board. Especially for milk and milk products, adulteration can be anything from water to urea, detergent, and starch. 

Adulteration in milk: What is it?

Adulteration of foods or adulterated milk means, an act of intentionally deteriorating the quality by adding or substituting substances of inferior quality before selling. Sometimes, valuable ingredients and nutrients are also altered or removed, adversely affecting the nature and quality of food.  ‘Adulterant’ materials are used to make the food ‘not safe for consumption 'as the nutritional value of the food falls or goes substandard. Milk and milk products can be regarded as adulterated when,

• The substance substituted depreciates its quality and purity.
• The addition of cheaper or inferior substances as a part or whole portion of the milk.
• A possibility of a low quality imitated milk or milk product is made and sold.
• Altered and colored to improve its physical appearance while compromising nutritional standards. 
• When substances dangerous to health are mixed. 

Adulteration in milk can be unsafe for consumption and cause long-term effects, nutritional deficiencies, impairment of growth and development, bone and teeth deformities, and many other problems. 

Tests to check the purity of milk 

FSSAI, under the Ministry of health and family welfare has shortlisted tests to detect the quality and purity of milk with household substances at home. These Rapid tests by Detecting Adulterants with Rapid Testing (DART) create awareness among the consumers, preventing food adulteration, consumer deception, and health risks. 

Test to check the water in milk

To test whether water is mixed with milk or not, 

• Put a drop of milk on a polished slanting surface.
• Pure milk either stays or flows slowly and leaves a white trail behind.
• Milk adulterated with water will flow immediately without leaving a mark.

Tests to check detergent in milk

To determine the mixing of detergent in milk for texture and lather, 

• Take 5 to 10ml of the sample with an equal amount of water.
• Shake the contents thoroughly.
• Milk adulterated with detergent forms a dense lather.
• Pure milk forms a very thin foam layer due to agitation.

Tests to check starch in milk and milk products (Khoya, chena, paneer)

The addition of starch in milk and milk products are identified with which colour the milk changes after boiling. The test can be done by,

• Boiling 2-3 ml of sample with 5ml of water.
• For ghee and butter, water addition is not needed.
• Cool the milk and add 2-3 drops of tincture of iodine.
• The formation of blue colour indicates the presence of starch.
• Also, milk does not require the addition of water after boiling. It does not get thick after boiling. However, starch in milk does. 

Other adulterant tests for milk

The other adulterants such as synthetic milk, and urea also can be tested at home 

Adulterants tested	Method of testing
Urea	Take a teaspoon of milk in a bowl. Add half a teaspoon of soybean or arhar powder, and mix up the contents thoroughly.  After 5 minutes, dip a red litmus paper for 30 sec.  If the red litmus changes to blue, the milk has urea.
Synthetic milk- made by adding white watercolour paints, oils, alkali, urea, and detergent.	Synthetic milk leaves a bitter aftertaste,  A soapy feeling when rubbed between the fingers,  And turns yellowish on heating

Conclusion

Food is an essential part of life. Food adulteration or milk adulteration is done intentionally to deceive consumers of high-quality, nutrition-rich, and safe-to-consume food. If you are suspicious of the milk quality and feel the need for testing, this article gives you an idea of how to check milk purity at home. And you can test for adulterants such as urea, detergent, water, and starch easily with household ingredients.