Detection of Adulterant in Dal


The objective of this experiment is to test for the presence of the adulterant ‘Metanil Yellow’ in dal.

The Theory

Metanil yellow is a principal non-permitted food colour used extensively in India. The effect of long-term consumption of metanil yellow on the developing and adult brain causes neurotoxicity. Neurotoxicity occurs when the exposure to natural or artificial toxic substances, alters the normal activity of the nervous system in such a way as to cause damage to the nervous tissue. Metanil yellow is used in dal as an adulterant for colouring. Its presence can be tested in dal by adding a few drops of HCl to a test sample, if the solution turns pink in colour, it indicates the presence of metanil yellow.


What is food?

Food is one of the essential factors in our daily life that provides nutritional support for the human body. Food supplies fuel for our body by providing it with many nutrients that are essential for good health. Most food has its origin in plants.

Many plants and plant parts such as leaves (spinach, lettuce), stems (bamboo, asparagus), roots (potatoes, carrots), and fruits (tomatoes, pumpkins) are used as food. Animals are used as food either directly (meat) or indirectly (eggs, milk). Ancient India produced food that was more than the required demand and people ate fresh food daily. We now buy food products from traders or manufacturers.

How pure is the food we consume?

We have all started thinking about the purity of the food we buy from traders. Due to the population explosion in India the demand for food has increased and traders have started mixing cheaper substances with food. These cheaper or undesirable substances added to food are called adulterants.

What is food adulteration?

Food adulteration is the process by which either toxic substances are added to food, or some valuable nutrients are removed from food items. Adulterated food is generally defined as impure, unsafe, or unwholesome food. Food adulteration may be done intentionally or unintentionally. Those traders or manufacturers who want to make a quick economic profit sell adulterated food intentionally. Unintentional adulteration happens when people are not aware of the rules, regulations and  methods of preparing wholesome food.

Government Act to Prevent the Adulteration of Food

The adulterants used by vendors are cheaper and sometimes toxic substitutes. Consumption of these food products can cause diseases like cancer, paralysis and skin allergy, etc. The government enacted the Prevention of Food Adulteration Act in 1954 to protect people from adulterated foods.

The organisations that issue certificates of reliability and purity of food items are:

  • Food Products Order (FPO)
  • Indian Standards Institute (ISI)
  • Agricultural Marketing (AGMARK)

Diseases caused by Adulterants

Some common adulterants found in our daily food products and the diseases caused by them are listed in the table below.

Food Adulterants Diseases Caused
Black pepper Dried papaya seeds Stomach irritation, liver damage, cancer
Chilly powder Brick powder, artificial colour Liver damage, stomach irritation
Arhar dal Metanil yellow, khesari dal Paralysis
Mustard Argemone Epidemic dropsy

Learning Outcomes

  1. Students understand the terms food adulteration and adulterant.
  2. Students understand the different types of adulterants used in food.
  3. Students acquire the skill to detect the presence of adulterants in different food samples after having observed the animation and simulation.