Food Adulteration And Rapid Tests For The Detection Of The Adulterants

Food adulteration takes into account the intentional or incidental addition or substitution or abstraction of substances that adversely affect the nature, substance, and quality of foods.



Food is the basic necessity of life and an idle food item should not only be available in sufficient quantity, but it should also be nutritious, safe, and wholesome. Pure food is essential for the maintenance of health and this is the reason one works very hard to earn bread and butter in order to satisfy his hunger.

However, in spite of this hard work, many of us do not make sure that we are eating the pure food which gives us energy and makes us healthy.

We are eating the foodstuffs contaminated with dangerous dye, sawdust, industrial starch, aluminium foil, carcinogenic substances, and so on. Due to this unwanted reason we often invite various diseases rather than good health.

Poor quality of food consumption by the people of any nation leads to malnutrition which in turn producing poor work efficiency. Thus, we can conclude that providing good quality food to the citizens of any nation has direct importance in respect of public health and the national economy.

Now before going through the topic deeper let us discuss the term adulteration. The Prevention of Food Adulteration (PFA) Act, 1954 and the Prevention of Food Adulteration Rules, 1955 are the main statutes in our country which protect the consumer and aim to provide him safe food.

As per the PFA Act, the term adulteration can be defined as “ Food adulteration takes into account not only the intentional addition or substitution or abstraction of substances which adversely affects the nature, substance, and quality of foods but also their incidental contamination during the period of growth, harvesting storage, processing, transportation, and distribution”.

Putting it simply, any material which is being employed to make the food unsafe, hazardous, or below the standard mark as set by the regulatory bodies is termed adulterated food. In a nutshell, food is declared adulterated if it satisfies any of the following points

  1. If the product offered or during processing contains any substance which harmfully diminishes its quality.
  2. Any cheaper or inferior substances are substituted wholly or in part in the product.
  3. Any natural constituent present in the product has been abstracted to affect its quality.
  4. If the product contains any prohibited coloring substances or preservatives or use of coloring matter exceeding the prescribed limit to make its appearance good.
  5. Whatever the reason may be if the product has the quality below the standard.

We will take an example of food adulteration that will simplify the term in a more lucid way.

According to the PFA Act, a milk seller can be found guilty if he is involved in any of the following scenarios:

  • If the seller adds water intentionally to the milk. This will be treated under the case of intentional addition of the substances from outside to make the quality of the product low.
  • If the seller replaces the fat content of the milk with some cheap vegetable oil or animal fat. This case will be under substitution of the components in the products.
  • If the seller completely removes all the milk fat and sells it as very low-fat content milk. This will be treated as an abstraction of the components from the products.
  • Not only that but unintentional contamination of the milk would also be treated as food adulteration under the law. For example, the seller uses his container for selling the milk. This container is poorly washed and may contain some chemical residues which are used for cleaning purposes. This kind of contamination is also treated as food adulteration.

One more point needs to be discussed here regarding the quality standards of the product. For example, as per the Food safety standards authority of India (FSSAI) regulation, the whole milk powder should not contain more than 4% of moisture.

Now, if a seller manufactured a milk powder and sells this product by obeying the above standards then the product is not adulterated but if it is not meeting the standard requirement it will be treated as a case of food adulteration.

Foods Commonly Adulterated:

As per the recent survey in our country majority of the food items got adulterated till it reaches our dining table. The trend of adulteration depends on several factors and it varies from region to region and state to state.

For example in the state of West Bengal mostly people use mustard oil for their cooking purpose so the likelihood of mustard oil adulteration is very high as compared to other edible oils.

On the other side, the ready availability of the adulterant is also a factor for food adulteration in certain states. Say in a place where the availability of cheap cottonseed oil is high then this would be used to adulterate the expensive edible oil such as groundnut oil.  The following are some general food items that are commonly found adulterated.

  1. Foodgrains like wheat, rice, pulses and their products like wheat flour, semolina (suji), gram flour (besan), etc.
  2. Edible oils and fats like groundnut oil, sunflower oil, mustard oil, Vanaspati, etc.,
  3. Spices, both whole, and ground, like red chilli powder, turmeric, coriander powder, Cumin powder, asafoetida (hing), saffron, cloves, ginger, cinnamon, black pepper, etc.
  4. Milk and milk products like milk powder, butter, ghee, khoa, sweets
  5. Coffee, tea, Confectionary, and baking powder
  6. Sweetening agents like sugar, honey, Jaggery
  7. Non-alcoholic beverages, juices, vinegar, besan, curry powder, etc.
  8. Fruits and vegetables

Food adulteration is not a new issue; actually, it is being practiced since ancient times. A common question that can arise in the mind of local citizens that where the necessity of food adulteration lies?? A very straightforward answer to this is greater profits by using minimum effort.

Food Adulteration is a very lucrative way of earning money in a short time frame and this is the reason dishonest traders do this even knowing that the impact of food adulteration is severely pushing people to the ill-health condition. Adding water to the milk and stones to the food grains and whole spices is one of the oldest forms of adulteration which people are practicing.

Poor quality of vegetables and fruits are sometimes being dyed to give its fresh look while some sweet makers use unhealthy and cheap aluminium foil instead of silver foil on the sweets. Sometimes traders bother about their product spoilage and in order to compensate for it, they often do food adulteration.

For example dry ginger develops holes on its surface due to insect attacks, this hole is being sealed with hazardous ultramarine blue as an adulterant.

Common Adulterants and their detection by rapid tests:

Adulteration of food cheats the consumer and possesses a serious health threat. A common citizen may not have adequate knowledge regarding the quality and the purity of the food artless he is buying from the market. We will discuss some common adulterants and their chemistry followed by the rapid tests so that people should be able to identify the correct product for their household use.

A-) Milk:

One of the important foods which everybody consumes in their daily life is milk. The common adulterants which are used in case of milk are water, starch, some preservatives like formalin, hydrogen peroxide, neutralizers like sodium bicarbonate, caustic soda, or any detergent powder.

Water is added to increase its volume and making more money easily while preservatives and neutralizers are often used in the summertime to increase its shelf life as in the summer milk spoils easily. Antibiotics, pesticide residues, and aflatoxin can also be hazardous substances found in milk sometimes.

Antibiotics can come to the milk due to the medication given to the cattle while pesticide spray in the cattle sheds is the possible source of the pesticides. If the cattle are being fed aflatoxin-contaminated feed then these contaminants can be found in the milk of the cattle. Now we will discuss few rapid tests to screen the milk.

Test 1: Detection of water in milk:

  1. Place a drop of milk on a polished, clean, and slanting surface
  2. Pure milk either stays or slowly moving to leave a white trail behind
  3. In the case of adulterated milk, it immediately flows without leaving a mark.
Figure 1: Rapid test for the detection of water in milk

Test 2: Detection of detergent in milk:

  1. 5 to 10 ml of the sample and water is taken at a 1:1 ratio
  2. The resultant solution is shaken vigorously
  3. Adulterated milk will form dense lather on the surface
  4. Pure milk will form a very thin foam layer
Figure 2: Rapid test for the detection of detergent in milk

Test 3: Detection of starch in milk and milk products( Khoya, chenna, paneer, etc.):

  • 2 ml of milk products were boiled with 5 ml of water.
  • In case of milk boiling and water addition step can be skipped
  • After cooling the solution few drops of iodine tincture are added.
  • The solution color turns dark blue that indicates the presence of starch.
Figure 3: Rapid test for the detection of starch in milk

Along with water and detergent, a very common adulterant is starch which is used to maintain the thickness of fat extracted milk or diluted milk. Tincture of iodine is the aqueous-alcoholic solution of iodine so we can say that the solvents are water and alcohol whilst the solute is iodine.

Iodine tincture mainly consists of 2% to 7 % of the iodine along with sodium iodide or potassium iodide which is required to generate iodide ion in the medium.

The resultant color of the solution is generally brownish orange. If it is added to a sample that contains starch the color changes to a deep blue. Questions arising in the mind how do these color changes work?  We will try to answer this in the following section.

Starch is a carbohydrate molecule that generally exists as a couple of molecules together named amylopectin (branched) and amylose (linear). Between them, amylopectin contributes around 65 to 85 %. That means amylose contributes very little as compared to amylopectin however interestingly it is amylose which is believed to react with iodine and gives dark blue color.

The reaction between starch and iodine is not very well understood however one explanation is that a charge transfer (CT) complex formation between starch and iodine is responsible for the color.  The addition of potassium iodide or sodium iodide facilitates the generation of iodide ions in the medium as iodine in its molecular form is insoluble in water.

Once the iodine generation started in the medium it further reacts with the molecular iodine to give the polyiodide ions (In–, for example,  I3–, I5–, or I7– etc). These polyiodide ions are absorbed in UV-Vis and producing brownish color. Once the amylose molecule of starch reacts with the polyiodides it forms another type of charge-transfer complex.

This CT complex absorbs light of a specific wavelength (of course different from that of polyiodide) and the dark blue color change took place. The spring shape like the amylose molecule is nothing but the polymeric form of a glucose molecule.  It is apprehended that the polyiodides are trapped in the coil of the beta amylose molecules thereby producing a dark blue color.

I2+ I = I3-

I3-+ I2 = I5-

I5-+ I2 = I5-  and so on ….

Figure 4:   Basic structure of a starch molecule

Figure 5:   Iodine bound in the starch helix to give dark blue color.

B-) Ghee/ Butter:

Ghee or butter is also an important food commodity that many people consume at home for good health development. The most common product which is consumed by the Indian household is ghee which is prepared from cow or buffalo milk.

It has significant importance from ancient times in fact many ayurvedic medicines require ghee for its formulation however with time passing it has lost its supremacy as well primacy as compared to the vegetable oil due to several reasons. Today it is mainly used for the purpose of any occasions or festivals.

Ghee or butter is often adulterated with mashed potatoes, sweet potatoes, or any other source of starches in order to make the appearance fattier. The following will illustrate the quick rapid test.

Test: Detection of starches (mashed potatoes, sweet potatoes, etc.) in ghee/butter

  1. Take one teaspoonful of ghee or butter in a transparent glass bowl.
  2. Add 4 to 5 drops of tincture iodine and mixed it properly.
  3. In the case of pure ghee/butter, no color change is observed.
  4. For adulterated ghee/butter dark blue color develops.
Figure 6: Rapid test for the detection of starch in ghee or butter

C-) Edible Oils:

Edible oil is mostly adulterated with the cheaper oil to make large profits investing a minimum amount. The cheaper oils are used may or may not be edible however this blending is taking place for the sake of profits only. The oils used are generally castor oil, argemone oil, rapeseed oil, mineral oil, palm olein, etc.

a-)-Test for the detection of other oils in coconut oil:

Coconut oil is used for many purposes like cooking, treatment of hair, skin, and many other health benefits. This oil is often adulterated with some cheap oil so that profits could be large.

Testing method:

  1. Pour some coconut oil into a transparent glass container
  2. Put this in a refrigerator (not a freezer). The oil gets solidified upon refrigeration.
  3. If the oil is adulterated with other oil, a separate oil layer is visible.


Figure 7: Rapid test for the detection of other oils in coconut oil

b-)-Test for the detection of the TOCP (Tri-ortho- cresyl- phosphate) in oils:

Tri-ortho-cresyl-phosphate or TOCP is an organophosphorus compound with anticholinesterase activity. The ortho isomers are thought to be more toxic than meta or para isomers. It causes a direct irreversible axonal damage of peripheral nerves which developed lasting motor neuropathy. TOCP is a chemical used as a fire retardant, plasticizer, or lubricant. It can be manufactured upon distillation of coal tar or petroleum products.

The absorption of this chemical is supposed through skin or mucosa that means if the edible oil is adulterated with TOCP it directly affects the skin even on rubbing the oil on the skin surface. Even today many people used to rub the mustard oil on the skin before bathing especially in the rural area. It can also be absorbed through the inhalation of the vapor while cooking thus led to damage the lung tissues severely.

TOCP is a very lucrative adulterant to dishonest traders because the color of this chemical is almost similar to the edible oil to be adulterated. Not only that surprisingly addition of this chemical to the edible oil does not affect its taste at all. A tragic incident of TOCP poisoning needs to be discussed in this regard to portray the severity of this adulterant.

TOCP Poisoning Tragedy:

TOCP poisoning tragedy took place in nearby Behala Buroshibtala poor slum dwellers locality, a suburb of Kolkata. The time when this incident took place actually a festival time about to come. The Rathyatra was about to come and the people were gathering many ingredients including edible oil for their cooking purposes.

The poor people could not afford expensive cooking oil rather they were dependent on cheap rapeseed oil and this compulsion of the poor people has been taken as a golden opportunity to earn few bucks by a  shop nearby named Garib Bhandar” (means shop for the poor).

They had bought the oil from this shop and keep consuming it. Initially, it was not showing any symptoms of illness among the people but after around two weeks people were found with severe toxicity having symptoms like vomiting and diarrhoea, later it quickly escalated into ascending motor paralysis.

The nearby Behala Vidyasagar hospital was flooded with sick patients and the doctors were trying hard to win in the battleground in order to save the lives.

Officially around 2500 people were affected but the unofficial source was quite higher than that. Upon investigation, it was found that the level of contamination with TOCP was found to be very high to the extent of even 57% in some of the samples. The dangerous outcome of this incident is irreversible toxicity which makes the survivors permanently disabled.

It was so devastating that even after 1.5 years of follow-up study it was observed that around 62.1% of the survivors had neurological disorders while only 37.9 % of the survivors recovered from motor paralysis.

One more important piece of data came up regarding this tragedy which was the recovery rate of the alcoholics. The alcoholics were showed an extremely slow response to their recovery due to the formation of the saligenin cyclic-o-tolyl phosphate which is the metabolite of TOCP and five times more toxic than the parent compound.

Testing Method:

  • Take around 2 ml of the oil sample in a transparent bowl
  • Add a little number of yellow butter cubes (solid)
  • Shake it properly
  • Immediate formation of red color indicates the presence of TOCP
Figure 8: Rapid test for the detection of TOCP in edible oil

D-) Sugars and Related Products:

a-) Detection of sugar solution in honey:

Honey has been regarded as nutritious food since ancient times due to its bioactivities and potential medicinal applications. The adulterations involve either the feeding of honeybees with sugar syrups or the deliberate addition of various sugar syrups that includes sucrose syrup, high fructose corn syrup, maltose syrup, etc.

Industrial-grade sugars like glucose and fructose are also used widely for this purpose In a nutshell; honey adulteration can be defined as a range of sugar syrups that are used to increase bulk volume, a common problem that has significant negative impacts on the honey industry from the economic as well customer satisfaction perspective.

Testing Method 1:
  • Pour water in transparent glass to fill it
  • Add a drop of honey to it
  • Pure honey will always settle down at the bottom but the dispersion of honey in a water medium is observed in the case of adulterated one.


Figure 9: Rapid test for the detection of sugar solution in honey
Testing Method 2:
  • Take a cotton wick  dipped wick with a honey
  • Burn it with a match stick
  • Pure honey will burn
  • Adulterated honey will not burn as it contains water molecules even if it burns it will have a cracking sound while burning.

b-) Detection of chalk powder in Sugar, pithi sugar, and jaggery powder:

Chalk powder is one of the most popular adulterants among dishonest traders who used to use this to increase the bulk weight of the products so that they can have larger profit by investing a minimum one.

Testing method:
  • Take a transparent glass of water.
  • Dissolve 10g of sample in water.
  • If the sugar or jaggery-related products are adulterated with chalk, settlement of the chalk powder at the bottom of the glass is the indication for the adulteration.
Figure 10: Rapid test for the detection of chalk powder in jaggery powder or related products

c-) Detection of aluminum leaves in silver leaves:

Adulteration in sweets is a common issue to address here. One such commonly available adulterated sweet are having silver leaf or chandi-ki-vark on it. The use of silver leaves is widely observed on a number of festival sweets, cakes, and other desserts. Silver leaf makes the sweet aesthetically pleasing which encourages people to gift it more at the festival time.

The eye-catching silvery look is not the silver metal that should be rather it contains most of the time metal like aluminium which is harmful to health. Although silver has antimicrobial properties and prevents the growth of bacteria on sweets the use of aluminium instead of silver makes it less significant.

Figure 11:  Sweets with silver leaf

It has been noticed that many times this so-called chandi ka varq contains not only aluminium but other harmful heavy metals like nickel, cadmium, and even lead. Moreover, a number of such sweets are prepared in unsanitary conditions, by sweet makers who don’t know how to use the proper and healthy manner.

Here I would like to mention that this silver leaf was one of the favorite ingredients in Mughlai and Awadhi cuisine like Shahi Tukda, Biryani, Korma, and Kebabs and in fact, the tradition of this still continues.

Figure 12: Use of silver leaf on (A) Lucknow biryani (B) Shahi kofta biryani (C) Navratan korma (D) Mughlai kebab chicken This Mughlai and Awadhi tradition continues today also where the silver leaf is used on betel leaf (paan), dry fruits, supari and elachi, and other foods also.

Figure 13: Silver coating on (A) Pistachio (B) Cashew (C) Almond (D) Betel leaf (Paan)

Generally, manufacturer or traders used coat their products with silver leaf due to the following reasons:

  • Provides a rich opulent look to foods
  • All of us know that Silver possesses antimicrobial properties which helps to prevent the growth of bacteria on sweets or the other food items
  • Silver leaf has a preservative property that helps food items including sweets to increase shelf life without adding any preservatives.

Adulteration in the silver leaf can be done by any of the following.

  • Substitution of silver with aluminum
  • Poor quality of silver used which is not of 999 purity or grade
  • method of preparation is Unhygienic
  • Traces of heavy metal contamination like nickel, lead, cadmium, etc.
Testing method:

Some portion of the leaves is crushed between two fingers. If the silver leaf is pure it is crushed to form the powder easily whilst if it is adulterated with aluminum it will not form a powder upon pressing rather the suspected leaves will break to produce smaller shreds only.

Another way to check the purity of silver is to burning in a flame. First, make a ball-like shape with the silver leaves and burn it in a flame.

If the silver leaf is pure it will form a sparkling shining ball which is also whereas aluminum will be completely burnt to produce grey ash only.

Figure 14: Rapid detection of aluminium leaves in silver leaves

E-) Foodgrains and Its products:

a-) Detection of rice bran in wheat flour:

Rice bran is added to the wheat flour as an adulterant to increase the bulk weight to gain more profit.

Testing method:
  1. Take a transparent glass of water.
  2. A teaspoonful of wheat flour is sprinkled on the surface of the water.
  3. Since bran is lighter than flour so if the flour is pure then no excess bran is floated on the water surface while in the case of adulterated flour excess bran can be observed easily floating on the water surface.
Figure 15: Rapid detection of rice bran in wheat flour

b-)-Detection of khesari dal in dal whole and split:

Kheasri dal is a cheap dal that is widely used as an adulterant in expensive dal like moong, tur, etc. The purpose is to increase the bulk weight to gain a large profit by investing a minimum.

Testing method:
  1. A little quantity of the suspected dal whole or split is taken in a clean glass plate.
  2. Examine the impurities visually.
  3. After visual inspection, if the dal found with an edged type appearance showing a slant on one side, indicates it is adulterated with Khesari dal while for pure dal no such observation is there.
Figure 16: Rapid detection of khesari dal in pure dal

c-)-Detection of added colors in food grains:

Foodgrains are often colored to give them a glossy look. These colors are very hazardous for human health. Long-term exposure can cause many diseases and sometimes life-threatening also.

Testing method:
  1. Take a transparent glass of water.
  2. A little number of food grains are poured into it.
  3. The resultant mixture is shaken for 2 minutes.
  4. Pure food grains will not leave any color while adulterated ones do immediately.
Rapid detection of added colors in food grain

d-)-Detection of turmeric in sella rice:

Sella rice is actually parboiled rice that contains yellowish color it due to the processing technique of the rice material. Golden sella is actually parboiled basmati rice. Due to the parboiling, the color of the rice turns into yellowish golden color so it named “Golden sella rice’.

The process of Par-boling involves the first step is soaking and steaming under the pressure of the paddy followed by proper drying preferably under the sun and finally it goes to the rice mill for milling.

The parboiling process is believed to be a more nutritious process than a normal one as it contains nutrients like thiamine (Vitamin B1). Due to this reason dishonest traders do coloring in the long grain basmati white rice or plain white rice with turmeric and give them golden yellow texture so that it can be shown to the consumers as parboiled rice.

Testing method:
  1. Add a little amount of rice to a glass plate and spread it.
  2. Spray a small amount of soaked lime on the rice grain surface and mix it. Soaked lime is commonly known as chuna which is used in a pan.
  3. Adulterated grains will form a red colour while pure ones will not.
Figure 18: Rapid detection of turmeric in sella rice


The chemical, curcumin is the active part of turmeric. It is nothing but a biphenol and can also be visualized as a1,3 diketone. They usually exhibit isomerization, well known as, keto-enol tautomerism. The tautomerism, extended conjugation, and aromatic phenolic rings in the structure of curcumin are responsible for the yellow color of curcumin.

Phenols are easily loose protons in the alkaline medium i.e in the presence of lime water or chuna. Due to this benzenoid structure of the curcumin converted into a quinonoid one. This transition is known to be a bathochromic shift in its optical property which means that the quinonoid form appears in a color that has a longer wavelength than its benzenoid form.

Putting it simply, lime water or chuna is a strong alkali (base) that neutralizes any of the two phenolic protons quickly and facilitates the conversion of the original benzenoid structure of curcumin with a yellow appearance into a quinonoid structure with red color. As red color has a higher wavelength than yellow so in that case when turmeric water gets contact with lime the color turns red.

Figure 19: keto-enol tautomerism in curcumin

e-)-Detection of rhodamine B in ragi:

In the food processed industry use of synthetic color is widely observed. These synthetic ones are preferred over natural ones as this color looks more attractive to the consumers and economically viable for the traders. Of course, these all synthetic colors must be permitted by one by the regulatory bodies before use.

Unfortunately, some of the illegal colors are also widely used by dishonest traders. These include Metanil Yellow, Rhodamine B (RB), Orange G, Pararosaniline (PA), Auramine O (AO), Sudan dyes, Blue VRS etc. These all colors are extremely harmful and carcinogenic. These are extensively used for food adulteration like sweets and confectionery and also food grains like ragi which is extremely nutritious millets.

Testing method:

1) A round-shaped cotton ball that is soaked in water or any vegetable oil is taken.

2) Outer surface of the ragi is rubbed with that ball.

3) Adulterated ragi will leave color on the surface of the cotton ball while pure one will not leave any color on the cotton ball surface.

Figure 20: Rapid detection of rhodamine B in ragi

F-) Salt, Spices, and Condiments:

Cheaper agricultural products like wheat starch, jowar; rice, corn, and arrowroot starch are used in a number of expensive foods like ground spices (red chilli powder, turmeric, coriander powder, garam masaIa, etc.). The color of starch is white and this characteristic of the starch has been used cleverly by the dishonest traders to do the food adulteration.

The starch is being dyed with the color of the spices and mixed to increase the bulk volume as to have greater profit by investing a minimum. Sometimes expensive spices like cloves are being adulterated by extraction of the clove oil and then sell it as it is.

Seeds of black pepper sometimes mixed with papaya seeds or light blackberries and mustard seeds may be mixed with cheap argemone seeds which look similar. Cinnamon bark is mixed with cassia bark which looks similar.

Asafoetida or hing is an important spice that is also adulterated with some foreign resin, soapstone powder having a similar texture. Chilli powder is mixed with synthetic color and sawdust.

a-)-Detection of papaya seeds in black pepper:

Testing method 1:
  • Add some amount of black pepper to a glass of water.
  • Pure black pepper settles at the bottom while adulterated one can be seen floating on the surface of the water
Figure 21: Rapid detection of papaya seeds in black pepper
Testing method 2:
  • Spread few black pepper seeds on a white paper
  • Observe carefully with a magnifying glass
  • Black pepper has brown color having a characteristic smell and a pungent taste
  • On the other side papaya seeds, a shrunken smooth surface having an oval shape with a greenish-brown or blackish-brown color possesses a repulsive smell.


Figure 22: Rapid detection of papaya seeds in the black pepper

b-)-Detection of light blackberries in black pepper:

Testing method:
  • Press the black peppers with the help of your fingers
  • Light blackberries will break easily while black pepper will not break
Figure 23: Rapid detection of light blackberries in black pepperDetection of foreign resin in asafoetida or hing:
Testing method 1:
  • Take a small quantity of asafoetida in a stainless-steel spoon and then burn it under the flame
  • Pure asafoetida will burn like bright flame camphor while for the adulterated one bright flame-like camphor was absent.


Figure 24: Rapid detection of adulterated asafoetida
Testing method 2:
  • Around one gram of asafoetida or hing is taken in a transparent glass container.
  • Add little water to it followed by proper shaking
  • Keep it few minutes  for further settlement
  • Milky white solution with no sediments represents pure hing while in the adulterated one sediment is present.

Figure 25: Rapid detection of adulterated asafoetida

c-)-Detection of soapstone powder in hing:

Testing method:
  • Around one gram of asafoetida or hing is taken in a transparent glass container.
  • Add little water to it followed by proper shaking
  • Keep it few minutes  for further settlement
  • If asafoetida is adulterated, soapstone or any kind of other earthy matter will settle down at the bottom
Figure 26: Rapid detection of adulterated asafoetida

d-)-Detection of starch in asafetida or hing:

Testing method:
  • Add few drops of tincture of iodine in an asafetida solution
  • If the color turns blue then it is adulterated if not then it is pure.


Figure 27:  Rapid detection of adulterated asafoetida

e-)-Detection of synthetic water-soluble colors in chilli powder:

Testing method:
  • Take little water in a clean transparent glass
  • Sprinkle a little chilli powder on it.
  • Pure chilli powder will not leave any color while adulterated one starts leaving color immediately
Figure 28: Rapid detection of artificial color in chilli powder

f-)-Detection of sawdust in chilli powder :

Testing method:
  • Add little chili powder in a glass container with water
  • Pure chili powder will settle down at the bottom while saw dust will float on the water surface.


Figure 29: Rapid detection of sawdust in chili powder

g-)-Detection of lead chromate in turmeric whole:

Lead chromate (PbCrO4) having a bright yellow color often used as a food color in varieties of food. It is generally added in sweets, turmeric powder, and turmeric whole to make its appearance bright yellow.

Testing method:
  • Take little water in a clean transparent glass
  • Add a small quantity of turmeric whole to it.
  • Pure turmeric will not leave any color.
  • If the turmeric is adulterated it will leave a bright yellow color quickly while for the pure one no such thing was observed

Figure 30: Rapid detection of lead chromate in turmeric whole

g-)-Detection of any artificial water-soluble color in turmeric powder:

Testing method:
  • Add a little turmeric powder in a glass container with water
  • Pure turmeric powder will produce light yellow color while settling down
  • Adulterated turmeric powder will give strong bright yellow color while settling down.
Figure 31: Rapid detection of soluble color in turmeric

h-)-Detection of sawdust and powdered bran in any kind of powdered spices:

Testing method:
  • Sprinkle powdered spices on the water surface.
  • Pure spices will not leave any adulterant (sawdust/powdered bran) on the surface of the water while in case of adulterated one adulterant can be seen floating on the surface.

Figure 32: Rapid detection of adulterated spices

i-)-Detection of chalk or any other white powder in common salt:

Chalk powder is mixed with common salt to increase its bulk weight and make a good profit by dishonest traders.

Testing method:
  • Add a teaspoon of a sample of salt in a glass of water and stir it thoroughly
  • Pure salt dissolves completely and gives a clear solution or gives slightly turbid solution due to the presence of the permitted ant caking agent in the salt.
  • In case of adulteration, the solution turns white and turbid with settling of insoluble impurities at the bottom
Figure 33: Rapid detection of chalk powder in common salt

i-)-Detection of exhausted cloves in pure cloves:

Cloves that are sold as spices are normally what we call ‘exhausted cloves,’ as they have the majority of their oils stripped from them. This makes them less powerful. Exhausted cloves can be identified by simply pressing them hard in between fingernails. If it releases oil then it cannot be exhausted. Testing method:

  • Take some water in a glass container and put some cloves in it
  • Pure cloves will settle down at the bottom while the exhausted cloves will float on the water surface.

Figure 34: Rapid detection of exhausted cloves in pure cloves

j-)-Detection of common salt and iodized salt:

Iodised salt(also spelled iodized salt) is a table salt that is mixed with a minute amount of other salts which contain the element iodine. The ingestion of iodine prevents iodine deficiency.

More than two billion people are affected globally due to iodine deficiency and which is one of the prominent causes of intellectual and developmental disabilities. The cause of “endemic goiter” is also due to the lack of iodine in the human body. The iodine deficiency is managed by adding small amounts of iodine to the table salt.

Testing method:
  • Take a piece of half potato
  • Sprinkle a little salt on it and wait for a minute.
  • Add two drops of lemon juice.
  • In the case of iodized salt due to the presence of iodine dark blue color develops while for common salt no color formation can be seen.
Figure 35: Rapid detection of common salt and iodized salt


The chemistry of the blue color formation can be visualized as follows

  • Iodized salt is “iodized” – i.e. it contains potassium iodide.
  • Lemon juice contains citric acid which could oxidize the iodide to elemental iodine.
  • Liberated iodine will react with the starch (from the potato) gives deep blue color.

k-)-Detection of cassia bark in cinnamon:

Testing method:
  • Take a clean glass plate
  • Add a small quantity of cinnamon to it
  • If the cinnamon is pure it appears to be a thin film that can be rolled around a pen or pencil. It also possesses a distinct smell while if it is adulterated it consists of several layers and it is different from the appearance of pure one.

Figure 36: Rapid detection of cassia bark in cinnamon bark

l-)-Detection of argemone seeds in mustard seeds:

Testing method:
  • Take a clean glass plate
  • Add a small number of mustard seeds to it.
  • Examine visually for the argemone seeds.
  • The surface morphology of the mustard seeds appears to be smooth and upon pressing the seeds yellow color can be seen inside it while for the argemone seeds surface morphology appears to be rough and upon pressing the seeds white color can be noticed inside it.
Figure 37: Rapid detection of argemone seeds in mustard seeds

m-)-Detection of grass seeds in cumin seeds:

The grass seeds are being colored with charcoal and mixed with similar-looking cumin seeds. In this way, whole cumin seeds are adulterated.

Testing method:
  • Take a small number of cumin seeds on palm
  • Rub it thoroughly
  • If palms turn black, adulteration is indicated.

Figure 38: Rapid detection of grass seeds in cumin seeds

F-) Fruits and vegetables:

According to the PFA Act, only some artificial or synthetic colours are permitted for use in foodstuffs. Colors other than the ones prescribed by law are referred to as non-permitted colors.

The most commonly used non-permitted synthetic colors reported in various studies are Orange 11, Sudan dyes, Metanil Yellow, Auramjne, Malachite Green, and Rhodamine B. These non-permitted colors are used as an adulterant in the fruits and vegetables to give it a fresh look.

a-)-Detection of malachite green in green vegetables like chili, bitter gourd, gourd, and others:

Testing method 1:
  • Take a small amount of cotton and make with it a small ball
  • Then this cotton ball is soaked with water or any vegetable oil.
  • The outer surface of the vegetables is rubbed with that soaked cotton ball
  • Upon rubbing if the color develops as green then malachite green adulteration is confirmed while if no color develops then the vegetable is unadulterated with malachite green.
Figure 39: Rapid detection of malachite green in vegetables
Testing method 2:
  • Take a few samples on a moistened white bloating paper
  • The impression of color on the bloating paper indicates the presence of malachite green or any cheap color.
Figure 40: Rapid detection of malachite green in green peas

b-)-Detection of artificial color on green peas:

Testing method:
  • Take a clean and transparent glass container
  • To it add a little number of green peas
  • Add water to it and mix well.
  • Let it stand for half an hour.
  • If the solution turns colorful then adulteration is confirmed while the clear solution indicates the pure green peas.

Figure 41: Rapid detection of artificial colors in green peas

c-)-Detection of rhodamine B in sweet potato:

Testing method:
  • Take a small amount of cotton and make with it a small ball
  • Then this cotton ball is soaked with water or any vegetable oil.
  • The outer surface of the sweet potato is rubbed with that soaked cotton ball
  • Upon rubbing if color develops then rhodamine B adulteration is confirmed while if no color develops then the sweet potato is unadulterated with rhodamine B

Figure 42: Rapid detection of rhodamine B in sweet potatoes

d-)-Detection of wax polishing on apple:

Since the waxy layer prevents moisture in the apple from escaping, so traders used to spray the apple with a thin layer of wax so that moisture loss can be prevented and the fruits look more attractive and fresh.

Testing method:
  • Take a knife and scratch the surface of the apple.
  • Wax comes out very easily if wax polishing has been done.

Figure 43: Rapid detection of wax in apple

H-) Beverages:

Beverages are also adulterated with various undesired materials say clay and chicory powder in coffee powder. Sometimes exhausted tea leaves are mixed with the pure tea leaves to increase the bulk weight thereby gaining more profit. During the tea processing, the dried tea leaves are cut with iron rollers.

After that, the tea powder is crushed with iron machinery and this is the source of fine iron particles in the tea. Although with the help of a huge magnetic force most of the iron particles get removed from the tea leaves however few particles did not separate and missed with the tea leaves as a powder.

The tea processing is designed like that one cannot be able to produce iron particles-free tea in fact it is unavoidable actually.

Due to this countries have their own maximum permissible limits keeping in view of the safe and allowed consumption of iron. For instance, Sri Lanka sets the limit as 200 milligrams per kilogram while in India FSSAI sets this limit as 250 mg/kg.

Similarly, chicory is not a coffee nor it does come from a coffee bean, it’s a chicory plant whose roots are roasted and finely powdered to add in a pure coffee as an adulterant.

a-)-Detection of clay in coffee powder:

Testing method:
  • Take a clean and transparent glass container
  • Fill the glass with water
  • Add a small quantity of coffee powder to it
  • Shaken the glass content for a minute and wait for 5 minutes
  • Settling of the clay particles at the glass bottom is the indication of the adulterated coffee powder while for pure one no such things happened.
Figure 44: Rapid detection of clay in coffee powder

b-)-Detection of chicory powder in coffee powder:

Testing method:
  • Take a transparent glass of water.
  • Add a teaspoon of coffee powder.
  • If the coffee powder is pure then it can be seen floating on the surface of the water while for the adulterated one the powder starts to sink.
Figure 45: Rapid detection of chicory powder in coffee powder

c-)-Detection of exhausted tea leaves in pure tea leaves:

Tea adulteration is one of the major and recurring issues in India. The Food Safety and Standards Authority of India (FSSAI) officials are often seizing teas adulterated with artificial colorants and dyes.

Low-quality teas including tea dust are the most suitable candidate for the traders to adulterate due to the cheap material availability. The adulterants for this purpose are used like sunset yellow, coal tar dyes, tartrazine, and any other colorants. These colorants used in the tea make it unfit for human consumption and endangering consumer health.

Testing method 1:
  • Take a clean filter paper
  • Put some tea leaves on it
  • Wet the filter paper with water
  • Wash the filter paper under tap water and notice the color change of the filter paper against the light
  • Pure tea leaves will not form any color stain while if coal tar dyes are present it will immediately stain the paper.
Testing method 2:
  • Take some tea leaves on a fresh filter paper
  • Add drop by drop water on the filter paper and rub the whole content gently on it
  • Pure tea leaves will not produce any color on the filter paper while colored teas will leave color on the filter paper.
Figure 46: Rapid detection of exhausted tea leaves in pure tea leaves

d-)-Detection of iron filings in tea leaves:

Testing method:
  • Take a clean glass plate
  • Add a small number of tea leaves to it
  • Move the magnet through the tea leaves.
  • No iron filings on the magnet are observed in the case of pure tea while for the adulterated one iron filings can be seen on the magnet.
Figure 47: Rapid detection of iron filings in tea leaves


In this article, we found that consuming pure food for every citizen of a nation is of paramount importance not only from the social health perspective also from the welfare of a whole community.

The local citizens are buying hundreds of products every day but at the end of the day, they do not even know that the products which he is buying for him and his family are good for health or not.

In this article, one effort has been given to identifying the adulterated products by performing some simple tests in-home so that people can be made aware enough regarding food adulteration.

It cannot be denied that all kind of food adulteration is not possible to catch by performing these simple tests because some adulterants are not detected by these experiments.

The complex tests need a sophisticated laboratory and the good news is that in our country many food testing labs which include government and private is running their facilities to test food adulteration. The main aim of this article is to make people aware of food adulteration and its harmful effects.

People can only approach the food testing labs for the product testing where they have some doubts about their own products when they know the subject “Adulteration” in a lucid way.

The subject “Adulteration” is a vast area to cover in a single article, however, the main emphasis has been given to the simple tests that can be performed in-home.

Therefore, writing this article would fulfill my effort only when people can try to do the testing at home and benefit from them. As I said earlier pure food consumption is a fundamental right for every citizen and by consuming pure food citizens will be healthy and able to build a prospective nation which all we dream of every day.


  3. IGNOU self-learning material, school of continuing education, MFN-003 Food Microbiology and Safety, Unit-8 Food Adulteration: Year of issue 2017
  4. Islam, Md Khairul, et al. “Sugar Profiling of Honeys for Authentication and Detection of Adulterants Using High-Performance Thin Layer Chromatography.” Molecules22 (2020): 5289.

Leave a comment