Detection of Common Adulterants in Food

What is adulteration in food? Addition of any non-condimental substance to a food Addition of substance injurious to health If the article sold by a vendor is not of the nature, substance or quality demanded by the purchaser Cheaper or inferior substance substitute wholly or partly for the article Article had been prepared, packed or kept under insanitary conditions

Detection of Adulterants Adulteration of sweets: Adulterated with unpermitted synthetic colors Sweets like jehangir, jilebi, savories like chowchow, potato chips contain metanil yellow and auramine Their consumption over a long period of time may cause gene damage, tumours and cancer

Adulterant Test method Metanil yellow auramine Take suspected sample in a petri dish, wet it with little warm water. Add a few drops of 1:3 dilute hydrochloric acid. Appearance of pink colour indicates metanil yellow. auramine Take suspected sample in a petri dish; add HCL. Decolourisation indicates the presence of auramine.

Silver foil in sweets

Silver Foil in sweets To give aesthetic appearance and to avoid stickiness while piling the sweets To increase the shell life of the product Dishonest traders use aluminium foil in the place of silver foil Cause Alzheimer’s disease Remove the foil from the sweets and transfer to a test tube; add 1-2ml HCL; Aluminium will dissolve while silver foil will not dissolve.

Adulteration of food grains

Adulteration of food grains Bengal gram dhal and toor dhal are commonly adulterated with kesari dhal Cheaper variety Cause lathyrism and crippling of lower limbs Detection: Physical test Chemical test Kesari dhal is square in shape and its surface is smooth with a slant on one side Bengal gram surface is ribbed Take suspected sample in a beaker and boil with 1:3 HCL for five minutes. The acid layer will turn pink if kesari dhal is present

Green dhal sometimes coated with synthetic colours To improve the appearance Put the dhal in water Colour if present will come out in water

Food Adulterant detection particle Pulses Metanil yellow dye Add HCL to a small quantity of dhal in a little amount of water. Immediate development of pink colour indicate the presence of metanil yellow. Lead Chromate Shake 5gm of pulse with 5ml of water and add a few drops of HCL. Pink colour indicate the presence of metanil yellow. Bajra Ergot infested bajra Swollen and black ergot infested grains will turn light in weight and will float also in water. Wheat flour Excessive sand and dirt Shake a little quantity of sample with 10 ml of carbon tetra chloride and allow to stand. Grit and sandy matter will collect at the bottom. Excessive bran Sprinkle on water surface. Bran will float on the surface. Chalk powder Shake sample with dilute HCL. Effervescence indicate the presence of chalk.

Milk and milk products

Milk and milk products Milk is adulterated with water indirectly by removing the cream. This introduces disease germs. Starch is added to make milk thicker. Water in milk Starch in milk Put a drop of milk on a polished surface and slant it slightly. Adulterated milk will flow quickly without leaving any white trail. Take suspected sample in a test tube and add tincture iodine solution. Appearance of blue colour indicates the presence of starch.

Detection of neutralizers in milk Neutralizers are added to avoid spoilage of milk Common neutralizers are sodium hydroxide, sodium carbonate and sodium bicarbonate. Take 5ml of milk in a test tube. Add 5ml of rectified spirit into it. Appearance of red colour or deep rose red colour indicates the presence of neutralizer. Brownish colouration indicates the absence of neutralizer.

Extraneous urea in milk Urea is added to milk as a preservative. It also adds viscosity to milk thereby giving a feeling of thick and rich milk. Take 5ml of milk in a test tube. Add 5ml of para-dimethyl amino benzaldehyde reagent to it. Appearance of distinct yellow colour indicates the presence of added urea.

Sodium chloride in milk To increase the density of milk. Take 2ml of milk in a test tube. Add 1ml of 5% potassium chromate solution and 2ml of 0.1N silver nitrate into it. The appearance of red precipitate indicates the presence of sodium chloride in milk.

Washing soda Chalk powder Adulterants in sugar Adulterant Detection Washing soda Chalk powder Take half a spoon of bura sugar in a test tube and add few drops of 1:1 hydrochloric acid. Immediate appearance of bubbles indicate the presence of washing soda in sugar. Take the sugar in a test tube and add a few drops of 1:1 hydrochloric acid. Immediate appearance of bubbles indicate the presence of chalk powder in sugar.

spices

Spices Spices and condiments are used in many recipes for its pungency , flavour and colouring power. Oil soluble colours to improve appearance. Cheap foreign starches. Argemone seeds are added to mustard seeds. Detected by physical appearance. Argemone seed is hard and round with a tip, dark in colour. Mustard seeds have a smooth and round surface without a tip.

Food particle Adulterant Detection Black pepper Papaya seeds, light berries etc. Pour the seeds in a beaker containing carbon tetrachloride. Black papaya seeds float on the top while the pure black pepper seeds settle down. Spices(ground) Powdered bran and saw dust Sprinkle on water surface. Powdered bran and saw dust float on water.

chillies

Chillies Chillies may be adulterated with brick powder grit, sand, dirt, filth etc. Oil soluble colours like Sudan Brick powder, sand, dirt etc. Pour the sample in a beaker containing a mixture of chloroform and carbon tetrachloride. Brick powder and grit will settle down at the bottom. Colour Pour the sample in a beaker containing a mixture of petroleum ether and diethyl ether. Decant the solvent concentrate and spot on a TLC plate. Distinct spots appear for oil soluble colour on developing with the solvent.

turmeric

Turmeric Adulterant Test Method Starch of maize, wheat, tapioca, rice. A microscopic study reveals that only pure turmeric is yellow coloured, big in size and has an angular structure , while foreign starches are colourless and small in size. Lead chromate Ash the simple. Dissolve it in 1:7 sulphuric acid and filter. Add 1 or 2 drops of 0.1% of diphenyl carbazide. A violet colour indicates the presence of lead chromate. Metanil yellow Add few drops of concentrated hydrochloric acid to sample. Instant appearance of violet colour which disappears on dilution with water, indicates pure turmeric. If colour persists metanil yellow is present.

Food Article Adulterant Detection Coriander powder Dung powder Soak in water. Dung will float and can be easily detected by its foul smell. Common salt To 5ml of sample add a few drops of silver nitrate. White precipitate indicates adulteration.. Badi Elaichi seeds Choti Elaichi seeds Separate out the seeds by physical examination. The seeds of badi elaichi have nearly palin surface without wrinkles while seeds of cardamom have pitted or wrinkled ends.

Food article Adulterant Detection Cumin seeds Grass seeds coloured with Rub the cumin seeds on palms. charcoal dust. If palm turns black adulteration is indicated. Asafoetida Soap stone, other earthy matter. Shake a little quantity of powdered sample with water. Soap stone or other earthy matter will settle at the bottom.

honey

ADULTERANTS IN HONEY Invert sugar/jaggery Fiehe’s test-add 5ml of solvent ether to 5 ml of honey. Shake well and decant the ether layer in a petri dish. Evaporate completely by blowing the ether layer. Add 2 to 3ml of resorcinol. Appearance of cherry red colour indicates the presence of sugar/jaggery. Aniline chloride test- Take 5ml of honey in a porcelain dish. Add aniline chloride solution and stir well. Orange red colour indicates the presence of sugar.

Coffee and tea

Food article Adulterant Detection Coffee and tea Food article Adulterant Detection Coffee chicory Take a measuring cylinder and fill it with water and gently sprinkle the coffee powder sample on the surface of water. Coffee floats over the surface of water but chicory begins to sink leaving a trail of brownish yellow colour. Tea synthetic colours Take a filter paper and spread the tea dust evenly. Sprinkle water to wet the filter paper. If synthetic colour is present, it will impart colour to filter paper.

Common Non-conformities found in Imported Food Products Food Item Observations Sweets & Colours-Allura Red, Quinoline Yellow. Added vegetable fat in chocolates. Confectioneries Low fat content in chocolates. Labeling Provisions- Manufacturers address, importers address in India not available. Date of manufacture. Best before or expiry date not available. In case of hard-boiled confectionery less than 20 g labeling provisions to be adhered in the multipack. Fruit Products Low net weight NO fruit juice content but contains fresh fruit flavour-declared as natural juice. Contains Allura Red and Quinoline yellow which is not permitted under PFA. Fruit juice containing spirulina under low concentrations-Declared as health drink but fruit juice content not declared. Labeling: Synthetic flavoured drinks containing figure of fruits. Manufacturers address. Importers address. Best before or expiry date not given.

OILS AND FATS

Oils and fats Food Article Adulterant Test Method Vegetable oil Castor oil Take 1 ml of oil in aclean dry test tube. Add 10 ml of acidified petroleum ether. Shake vigorously for 2 minutes. Add one drop of ammonium molybdate reagent. The formation of turbidity indicates presence of castor oil in the sample. Argemone oil Add 5ml of concentrated nitric acid to 5ml sample. Shake carefully. Allow to separate. Yellow, orange yellow and crimson colour in the lower acid layer indicates adulteration.

Detection of sesame oil in edible oils- Baudouin Test take 5ml of oil in a 25ml measuring cylinder. Take 5ml HCL and 0.4ml furfural solution. Insert glass stopper and shake vigorously for 2 minutes. Allow the mixture to separate. Development of pink or red colour in lower acid layer indicates the presence of sesame oil. Confirm by adding 5ml of water and shake again. If colour disappears, sesame oil is absent

Detection of palmolein in groundnut oil-cloud test Heat 60-75 gram sample to 130°C. Pour 45ml of heated fat into an oil sample bottle. Place the bottle in water a bath. Begin to cool the bottle in the water bath, stirring to keep the temperature uniform. When sample has reached the temperature 10°C above cloud point, stir steadily and rapidly in a circular motion. Cloud point is that temperature at which the first turbidity appears. Remove the bottle from the bath and read the temperature. Presence of palmolein over 10% in groundnut oil readily gives cloud at a higher temperature than that of groundnut oil.

Detection of animal fat in vegetable fat Microscopic Examination Take about 2 gram melted fat sample in test tube. Mix with 10 ml diethyl ether. Plug the tubes with cotton and leave for thirty minutes in ice bath. Keep it for 24 hours at 20°C (crystallization) Place the crystals on a drop of glycerin previously taken on a microscopic slide. Cover the crystals immediately with cover glass. Examine under x160 and finally x400 magnifications. Beef tallow crystals appear in the shape of characteristic fan like tufts, the end of which are pointed. Hydrogenated fats deposit smaller crystals.

Detection of mineral oil in edible oil- Holde’s Test Take 22 ml of alcoholic KOH in a conical flask. Add 1 ml of sample of oil to be tested. Boil on a water bath using an air condenser till the solution becomes clear and no oily drops are found. Transfer the contents to a warm test tube. Add 25 ml of boiling distilled water along the sides of the test tube. Keep on shaking the tube. Turbidity indicates the presence of mineral oil.

Detection of oil soluble coal tar dyes in oils Take 5 ml of oil sample in a conical flask. Add 25 ml of hexane followed by 10g silica gel and 2g anhydrous sodium sulfate. Stir the mixture and leave for 5 minutes. Decant off the solvent. Add again 25 ml of hexane and stir, decant. Repeat this process 3-4 times. Elute the colour absorbed by silica gel with diethyl ether 2 to 3 times. Evaporate ether. Spot on a TLC plate and develop in a tank containing solvent mixture. Remove the plate and heat at 100°C in an oven for 1 hour. Natural colours would fade away on heating.

Adulteration in ghee Adulterant Detection Mashed potato, sweet potato etc. Vanaspati Rancid stuff(old ghee) Synthetic colour Boil 5 ml of sample in a test tube. Cool and add a drop of iodine solution. Blue colour indicates the presence of starch. Take 5 ml of sample in a test tube. Add 5 ml of HCL and a few sugar crystals. Insert the stopper and shake for 2 minutes. Development of pink or red colour indicates the presence of vanaspati in ghee. Take 1 teaspoon of melted sample and add 5 ml of HCL. Shake vigorously for 30 seconds. Add 5 ml of phloroglucinol solution and shake for 30 seconds. Allow to stand for 10 minutes. A pink or red colour in the acid layer indicates rancidity. Dissolve 2g ghee in ether. Divide into 2 portions. Add 1 ml of HCL to one tube and 1 ml of 10% NAOH to other tube. Shake well and allow to stand. Presence of pink colour in acid solution or yellow colour in alkaline solution indicates added colouring matter.