How To Check

Milk Adulteration

In India?

Milk adulteration is a process in which the quality of milk is intentionally degraded; i.e., it is not spoiled over time due to improper storage or exposure, but is a subpar product to start with. Milk can be adulterated by adding inferior or harmful substances (like water, starch, detergents, urea, or formalin) to increase volume and shelf life, or by removing milk fat (cream). The motive is almost always to increase profit.  

You can perform a few quick visual checks before buying and more reliable tests after purchasing. Milk adulteration tests before purchasing can be useful, but are not as in-depth or reliable as the tests conducted after purchasing the milk. It also depends on whether the seller lets you test the milk before purchasing. If you test beforehand, though, then you can decide before buying. If you test it after buying, you may have to discard it if it’s adulterated. 

Before purchasing milk, you can opt for two kinds of tests: the slope or drop test and the shake test. In the first one, drop a single drop of milk onto a clean, slanted steel plate or polished surface. Pure milk moves slowly and leaves a distinct, white trail. If it flows very quickly and leaves little trail, the milk may be diluted with water. For the shake test, take a small sample of milk in a bottle and shake it vigorously for a few seconds. Pure milk will produce very thin, quickly disappearing foam. If a dense, long-lasting lather forms, it may contain detergent.

Pure milk has a mildly sweet and natural odour. If it has a chemical, soapy, or detergent-like smell, or if it tastes bitter, it is likely synthetic or adulterated. Another way to test for synthetic milk (not dairy but a mix of ingredients) is to rub a drop between your hands. Real milk is slightly creamy and remains white when boiled, but synthetic milk may develop an unusual soapy smell, separate abnormally on boiling, or leave an oily film. Always combine sensory tests with another test (such as boiling), as your sense of touch, smell, and taste may be affected by other factors.

If you have already purchased the milk and want to check for specific chemical adulterants, FSSAI recommends two home methods: the Starch Test and the Litmus Test. For the starch test, start by boiling 3 ml of milk with 5 ml of water. Let it cool, and add 2–3 drops of tincture of iodine. If the milk turns blue, starch has been added to make the milk look thick. The Litmus Test includes mixing a teaspoon of milk with a half teaspoon of soybean or arhar (pigeon pea) powder. Shake it thoroughly and let it sit for 5 minutes. Dip a red litmus paper into the mixture; if the paper changes to blue, urea is present.

If you’re opting for packaged milk, packaging and storage integrity are important. Firstly, always check the seal. Never buy a packet with visible tears, punctures, or swelling (swelling indicates bacterial gas formation). Secondly, only buy from retailers who store milk in chilled display cabinets or refrigerators. Avoid purchasing packets that are kept out in the open, especially in warm weather. You can also opt for tetra packs (UHT milk) because they are sterilised to last and have a longer shelf life. 

Just as it’s important to check storage before buying packaged milk, it’s also important to securely seal open packets. Ideally, don’t keep it for too long, even when refrigerated. Because milk is highly perishable once exposed to air, consume it within 2–3 days. If you're not boiling it right away, seal the packet with a clip or store the poured milk in an airtight glass container. 

Boiling milk is one of the simplest ways to make it safer for consumption. Heating destroys most disease-causing bacteria that may be present in raw or improperly handled milk and extends its shelf life by slowing bacterial growth. However, packaged pasteurised milk has already been heat-treated and is microbiologically safe. Many households still boil it after opening as an extra precaution and to maintain a long-standing kitchen practice.

While a few simple home tests can help identify obvious adulteration, no single method can detect every contaminant. The safest approach is to purchase milk from trusted brands or reliable local dairies, store it properly refrigerated, and pay attention to any unusual smell, texture, or taste. If you suspect milk adulteration despite these checks, avoid consuming it and report the issue to your local food safety authority.