FOOD CONTAMINATION & FOOD ADULTERATION
Food adulteration of food stuff is commonly practiced in India by the trader. Adulteration defined as the process by which the quality or the nature of a given substance is reduced to
• • The addition of a foreign or an inferior substance.
• • The removal of vital element.
According to PFA Act
Food Adulteration includes
1. Intentional addition, substitution or abstraction or substances which adversely affect the purity and quality of foods.
2. Incidental contamination of foods with deleterious substances such as toxins and insecticides due to ignorance, negligence, or lack of proper storage facilities.
3. Contamination of the food with harmful insects, micro-organism like bacteria, fungus, molds etc. during production, storage, and handling.
TYPE OF ADULTERANT
Adulterants may be intentional or unintentional. The former is a wilful act on the part of the adulterator intended to increase the margin of profit. Incidental contamination is usually due to ignorance negligence or lack of proper facilities.
1. INTENTIONAL ADULTERANTS
Intentional adulterants are sand, marble, drip, stone, mud, chalk powder, water, mineral oil and coal tar, die the adulterants cause harmful effects on the body.
Name of the food article | Adulterant | Simple method for detection of adulterant |
Asafoetida | Soap stone (pumice stone) or other earthy matter Starch Chalk | Shake with water, soap stone or other earthy matter will settle to the bottom. Same tests as in the case of milk. Shake sample with carbon tetrachloride. |
Bajra | Infested with Ergot | Long irregular black grain indicates ergot. In 2 per cent salt solution ergot floats. |
Rubbing with fingers and roughness indicates presence of maize flour. Shake portion of sample with cold or warm water. The water becomes yellowish and on treatment with few drops of concentrated HC1 turns magnets red. | ||
Papaya seeds are shrunken, oval in shape and greenish brown or brownish black in colour and have repulsive flavour quite distinct from the bite of black pepper. Light Berries or papaya seeds float on spirit or carbon tetrachloride. | ||
Chilli powder | Brick powder. Soap stone Artificial colour | sediment at the bottom of glass confirms the presence of brick powder or sand. Smooth white residue at the bottom indicates the presence of soapstone. Water soluble artificial dye can be detected by sprinkling a small quantity of chilli or turmeric powder on the surface of water contained in a glass tumbler. The soluble dye will immediately start descending in colour streaks. |
Cinnamon | Cassia bark | Cinnamon barks are very thin and can be rolled. Cassia barks are thick and stiff. |
Cloves | Volatile oil extracted Cloves | Exhausted cloves can be identified by its small size and shrunken appearance. The characteristics pungent taste of genuine cloves is less pronounced in exhausted cloves. |
Coffee | Chicory Starch Tamarind or date-seed Powder | Gently sprinkle the coffee powder sample on the surface of water in a glass. The coffee floats over the water but chicory begins to sink down within a few seconds. The falling chicory powder particles leave behind them a trail of colour due to large amount of caramel they contain. Make decoction of the coffee, decolourise it by adding potassium permanganate and then add a drop of iodine solution. Blue colour indicates presence of starch. Sprinkle the suspected coffee powder on white blotting paper and spray over it 1 per cent sodium carbonate solution. Tamarind and date-seed powder will, if present, stain blotting paper red. Shake powder with 2 per cent sodium hydroxide or washing soda solution. Formation of reddish colour indicates tamarind seeds. |
Common salt | White-powdered stone, chalk | Stir a spoonful of simple salt in a glass of water. The presence of chalk will make the solution white and other insoluble impurities settle down. |
Coriander powder | Common salt | To 5 ml of sample add a few drops of silver nitrate. White precipitate indicates adulteration. |
Cumin seeds | Grass seeds coloured with charcoal dust | Rub the cumin seeds on palms. If palms turn black adulteration is indicated. |
Dal | Kesari dal Clay, stones. gravels lead chromate. metanil yellow | Add 50 ml of dilute hydrochloric acid to dal and keep on simmering water for about 15 minutes. The pink colour if developed indicates the presence of kesari dal. On visual examination to see wedge like shapes of Kesari dal. Visual examination will detect these adulterants. Shake 5 grains of dal with 5 ml of water and add a few' drops (yellow) of hydrochloric Acid. A pink colour shows the presence of colour. |
Edible oils | Argemone oil Mineral oil Castor oil | Add concentrated nitric acid to a sample and shake carefully. Red to reddish brown colour in acid layer indicates the presence of argemone oil. Take 2 ml of edible oil and add an equal quantity of N/2 alcoholic potash. Heat in boiling water bath for 15 minutes and add 10 ml of water. Any morbidity shows the presence of mineral oil. Dissolve some oil in petroleum ether in a test tube and cool in ice salt mixture. Presence of turbidity within 5 minutes indicates the presence of oil. * This test is not for minute traces. |
Food grains | Hidden insect infestation | Take a filter paper impregnated with ninhydrin (1% in alcohol). Put some grains on it and then fold the filter paper and crush the grains with hammer. Spots of bluish-purple colour indicate presence of hidden insects’ infestation. |
Ghee or Butter | Vanaspati Mashed potato, sweet potato and other starches. | Take about one teaspoonful of melted ghee or butter with equal quantity concentrated hydrochloric acid in a test tube and add to it a pinch of cane sugar. Shake well for one minute and test it after 5 minutes. Appearance of crimson colour in lower (acidic) layer shows the presence of 'vanaspati’. This test is specific for sesame oil which is compulsorily added to vanaspathi. Some of coal tar dyes also give a positive test. Add a drop of iodine solution. Iodine which is brownish in colour turns to blue if starches are present. Iodine solution is prepared by dissolving 2.5 g of iodine crystals and 3 g potassium iodine in water to make solution of 100 ml. |
Honey
| Molasses (sugar and water)Commercialinvert sugar(mixture of fructose) Jaggery | A cotton wick dipped in pure honey when lighted with a matchstick burn. If adulterated the presence of water will not allow the honey to burn. If it does, it will produce a crackling sound. 1 Fiehe’s test. Mix 5 g of honey with 10 ml of ether in a mortarusing a pestle. Decant the ether extracts into a China dish. Repeat twice or thrice. Allow the ether to evaporate at room temperature. Of freshly sublimed resorcinol in concentrated HC1 (1 g of resorcinol resublimed in 5 ml of conc. HC1). Immediate appearance of cherry red colour indicates invert sugar. 2. Aniline chloride test. Take 5 ml of honey in a porcelain dish. Add Aniline chloride solution (3 ml of aniline and 7 ml of 1:3 HC1) and stir well. Orange red colour indicates presence of sugar. |
Jaggery powder sugar | Chalk powder Metanil yellow | Add few drops of hydrochloric acid. Effervescence indicates adulteration. Stir a spoonful sample of sugar in a glass of water. The chalk settles down. Same test as for other substances. |
Khoa | Starch | Add tincture of iodine. Indication of blue colour shows the presence of starch. |
Milk | Water/Deflated milk Starch | a. The lactometer reading should not ordinarily be less than 1.028. b. The presence of water can be detected by putting a drop of milk on a polished vertical surface. The drop of pure milk either stops or flows slowly leaving a white trail behind it; whereas milk adulterated with water will flow immediately without leaving a mark. c. Add tincture of iodine, indication of blue colour shows the presence of starch. * This test is not valid if milk is skimmed, and thickening material is added. |
Milk. Curd | Cane sugar | Add 0.1 g of resorcinol and 1 ml of concentrated HC1 to 10 ml of the sample and boil—A rose red colour indicates the presence of cane sugar. |
Mustard seeds | Argemone seeds | Examine under magnifying glass. Seeds more blacken, rough and non-uniform irregular round show presence of argemone seeds. Mustard seeds have a smooth surface. The argemone seed have |
Powdered spices | Grit, talc sand colour | grainy and rough surface and are blacker hence Shake up a little of the sample in a dry test tube with 5 ml of carbon tetrachloride (CC14). Allow to settle sand, talc and grit will sink to the bottom leaving spices on the top. |
Pulses (green peas) | Colour dye | Sample is kept immersed in water for about half an hour and stirred. Colour separation indicates adulteration. |
Rava | Iron fillings | By moving a magnet through its iron fillings can be |
Rice | Marble or other stones | A simple test is to place a small quantity of rice on the palm of the hand and gradually immerse the same in water. The stone chips will sink. |
Saffron
| Dyed tendrils of maize cob | Genuine saffron will not break easily like artificial one. The colour dissolves in water if artificially coloured. Pure saffron when allowed to dissolve in water will continue to give its saffron colour so long as it lasts. |
Sago | Sand or talcum | On burning leaves no ash. Adulterated sago will leave behind appreciable quantity of ash. |
Silver leaves | Aluminium leaves | On ignition, genuine silver leaves bum away completely, leaving glistening white spherical ball whereas aluminium leaves are reduced to ashes of dark grey blackish colour. The silver foil is very thin and if crushed between two fingers, crumbles to powder Aluminium foil is comparatively thicker and only breaks to small shreds when passed similarly. Take silver leaves in a test tube. Add dil HC1. Appearance of turbidity to w'hite precipitate indicates the presence of silver leaves. Aluminium |
leaves react with HC1 to leave blackish grey fumes. | ||
Soft drinks | Mineral acid other than phosphoric acid | Soak a strip of filter paper in a 0.1 per cent solution of metanil yellow and then dry. Dip one end of paper into the soft drink. Wetted portion turns violet if mineral acid in present. |
Sugar | Chalk powder | Dissolve in a glass of water, chalk will settle down at the bottom. |
Supari | Colour and saccharin | Colour dissolves in water. Saccharin gives excessive and lingering sweet taste. |
Sweet meat. Ice-cream, Sherbet | Metanil yellow (a non-permitted coal tar dye) | Extract colour with Luke-warm water from food article. Add few drops of conc. Hydrochloric Acid. , If magenta red colour develops, the presence of metanil yellow is indicated. |
Tea leaves | Exhausted tea or black or bengal Gram dal husk with colour | a. Tea leaves sprinkled on wet filter paper would immediately release added colour. Spread a little slaked lime on white porcelain tile or glass plate. Sprinkle a little tea dust on the lime. Red, orange or other shades of colour spreading on the lime will show the presence of coal tar dye. In the case of genuine tea, there will be only a slight greenish yellow colour due to chlorophyll which appears after some time. |
Turmeric | Metanil yellow, yellow clay | Take a teaspoon full of turmeric powder in a test tube. Add a few drops of conc. hydrochloric acid. Instant appearance of violet colour which disappears on dilution with water. If the colour persists, presence of metanil yellow is indicated. Mix powders with water and allow to stand for some time. The yellow' clay will settle down at the bottom leaving turmeric on the top. |
Wheat, bajra and other food grains | Ergot (a fungus containing a poisonous substance) Dhatura-seeds | Purple black longer size grains in bajra show the presence of ergots. Dhatura seeds resemble chilli seeds with blackish brown colour which can be separated out by close examination. |
Wheat flour | Maida | When dough is prepared from resultant wheat flour, more water has to be used and chapathies prepared out of this will blow out. The normal taste of chapathies prepared out of wheat is somewhat sweetish whereas those prepared out of adulterated wheat flour will taste insipid. |
| Chalk powder and lime powder | Treat sample with hot dilute HC1. The bubbling of gas indicates carbon dioxide from chalk or other carbonates. |
2. INCIDENTAL ADULTRATION
• Contamination of foods with harmful micro-organisms
Raw foods such as meat. fish, milk and vegetables grown on sewage are likely to be contaminated with harmful microorganisms. These are generally destroyed during cooking or processing of food. Some of the micro-organisms may survive due to inadequate heat processing. Further, some of the foods, if consumed in the raw state, may cause food poisoning. Recent studies have shown that food grains, legumes and oil seeds when stored in humid atmosphere are infected by pathogenic fungus which can cause serious illness. The pathogenic micro-organisms commonly contaminated foods and responsible for causing serious illnesses are listed in the Table 14.2 and are briefly described.
• Metallic contamination
Lead is a toxic element and contamination of food with lead can cause toxic symptoms. For example, turmeric is coated by illiterate manufacturers in India with lead chromate. Lead brings about pathological changes in the kidneys, liver and arteries. The common signs of lead poisoning are nausea, abdominal pain, anaemia, insomnia, muscular paralysis and brain damage. Fish caught from water contaminated with mercuric salts contain large amounts of mercury. The organic mercury compound methyl or dimethyl mercury is the most toxic. The toxic effects of methyl mercury are neurological. When the brain is affected, the subject becomes blind, deaf and paralysis of the various muscles make him a cripple. The other elements which are toxic in small doses are cadmium, arsenic, antimony, and cobalt.
Studies conducted (2006) by scientists at Industrial Toxicology Research Centre, Lucknow, found that silver foil used for sweets and in pan masala contain carcinogenic nickel, lead, chromium and cadmium. Silver metal is transformed into the thin foil used in sweets by workers in small factories who fill the metal in a leather bag and beat it with a wooden club. No purification process is carried out before making foil. Silver foil with a purity of 99.9 per cent can be used in edible form
A survey conducted by the Indian Council of Medical Research (ICMR) also found high levels of pesticide residues in bovine milk and metals arsenic, cadmium and lead in infant formula canned products and turmeric.
Indian chocolates are high in nickel, a trace metal that could cause cancer. This is present in soil, water, hydrogenated vegetable oil and even in milk. Through milk or other ingredients chocolates have nickel. According to WHO, the normal consumption is 100-800 meg of nickel every day. This may not affect our well-being. There are no Indian standards nickel could accumulate in the body over a period.
Other incidental adulterants
a) 
The Argaemone mexicana is frequently found growing in brassica fields and if proper care is not taken during cultivation its seeds get mixed with those of brassica and the oil expressed contains also argemone oil. Its presence in edible mustard oil is injurious and outbreaks of epidemic dropsy are probably due to it.
b) Wood smoke which contains chlorodioxins is toxic and contaminate the food coming in contact with the smoke.
c) Pests such as rodents and insects introduce into the food a high degree of filth in the form of excreta, bodily secretions and spoilage micro-organisms. Leptospirosis is caused by the contamination of urine of rat. Infected urine of rat contains spirochaetes which can penetrate the skin or mucosa of man. Effective means of food quality can be achieved by legislative measures, certification schemes and public participation and involvement in the programme.
d) The most common incidental adulterants are pesticides. DDT and malathion residues may be present on the plant product much more than what is considered as safe. The maximum permissible residue allowed for DDT, malathion is 3 ppm and for pyrethrum it is 10 ppm.
e) Chemicals like DDT are absorbed by the small intestine when ingested. These then adhere to the fatty tissues—the toxins usually pile up in the fatty tissues of such vital organs as the thyroid, heart, kidney, liver, mammary gland and testes and damage these organs. They can be transferred from the umbilical cord blood to the growing foetus and through breast milk. In children the disease apart from crippling them inhibits their growth.
This incidental poisoning can be prevented by:
• regular market surveys to warn people of dangerous build-up of toxins in food.
• stepping up the integrated pest-management programme to teach farmers to use pesticides judiciously. No* spraying should be done a week, before harvest.
• taking up on a war footing the control of pests using their natural predators.
• using safer pesticides like synthetic pyrethroids or malathion.
• by washing vegetables thoroughly before cooking.
Packaging hazards
Polyethylene, polyvinyl chloride and allied compounds are used to produce flexible packaging material. While this method of packaging is very convenient, it must not contain any noxious thermal breakdown products which could be injurious to health. Further, temperatures used for heat sealing, or sterilisation should not result in formation of toxic residues. It has been observed sometimes that in foods like pickles the acid and oil could attack the plastic packaging material and create a health hazard. To avoid such incidences, it is essential that only food-grade plastic packaging materials be used for packaging foods. New adulterants
- The newer adulterants include the legumes such as imported toxic lentils marketed as local lentils, local legume like Subabul (Lencana leucocephala) seeds, veterinary drug residues in milk, flours made from mouldy wheat, strychnos potatorum, a forest produce in arecanut, animal fat in bakery products and industrial contaminants like orthonitro aniline in vanaspati.
- · The Lalhyrus sativus, Lens Culinuris(lentils) and Vicia sateva are three closely related species containing unusual amino acids.
- · Turkish lentil which was sold in India as Red gram (Cajanas cajan) dal and Australian vetch (Vicia sativa) sold as Indian masur dal (Lens culinaris) Vicia sativa is a weed found among other edible legumes and used in India only for feeding farm animals. Vicia sativa contains the toxic amino acid p- cyanoalamine, Turkish yellow lentils contain the diaminopropionic derivatives.
- · Ginger is used widely in culinary practice in India in the fresh or dry states. Dry ginger is often coated with a blue-coloured dye ultramarine blue to prevent insect infestation. It is an inorganic pigment used as laundry whitener. In USA and Canada, its use is restricted to addition in salt meant for animal consumption.