by-DR. RAJESH KUMAR SINGH, (LIVESTOCK & POULTRY CONSULTANT), JAMSHEDPUR, JHARKHAND,INDIA 9431309542, rajeshsinghvet@gmail.com
Food adulteration is a serious issue which has needed to investigate as a potential food safety and public health concern in recent years . Food fraud for economic gain has been prevalent throughout history for as long as food has had economic value as commodities. Economically motivated adulteration, a subset category of food fraud, was defined in 2009 by the Food and DrugAdministration (FDA) as “the fraudulent, intentional substitution or addition of a substance in a product for the purpose of increasing the apparent value of the product or reducing the cost of its production,” and can often encompass effects public safety through the unknown addition of allergens, toxins, and hygienic risks .
India is today the world’s largest producer of milk thanks to the white revolution. Yet more than two thirds of the milk in India does not meet the food safety standards. Adulteration of milk is rampant, a startling six per cent of the samples tested in 2015 by the Ministry of Health had presence of ‘detergents’ in them confirming that ‘synthetic milk’ is a huge problem.
For a lay person trying to differentiate between contaminated and pure milk is a tall order and only specific chemical tests can reveal the truth. Contaminated milk can be a huge health hazard especially when it has been laced with urea, detergents and other toxic chemicals. With the festival of Holi round the corner, it is time to be alert about the dangers of milk contamination.
Now a cheap milk testing kit has been developed by the Defence Food Research Laboratory (DFRL) in Mysuru, which is a part of the gigantic Defence Research and Development Organisation (DRDO). This kit, which even an untrained person can use at home, helps within minutes detect contamination of six common adulterants in milk.
The National Survey on Milk Adulteration 2011 conducted by Food Safety & Standards Authority of India located at Chennai, Mumbai, Delhi, Guwahati and Kolkata in 33 States to determine the quality of milk and identify common adulterants in loose & packed milk. The total non-conforming samples were 1225 (68.4%).
While Mizoram, Chhattisgarh, Daman & Diu, Jharkhand, Orissa, West Bengal & Mizoram had 100% while Goa & Puducherry had 0% contamination. All samples from these two states conformed to the standards.
Basic Contaminants – Water, Detergent, Skim Milk Powder, Glucose etc.
What is Adulteration?———
Food Adulteration is an act of intentionally debasing the quality of food offered for sale either by the admixture or substitution of inferior substances or by the removal of some valuable ingredient, Food Adulteration takes into account not only the intentional addition or substitution or abstraction of substances which adversely affect nature, substances and quality of foods, but also their incidental contamination during the period of growth, harvesting, storage, processing, transport and distribution.
“Adulterant” means any material which is or could be employed for making the food unsafe or sub-standard or misbranded or containing extraneous matter;
Food is adulterated if its quality is lowered or affected by the addition of substances which are injurious to health or by the removal of substances which are nutritious. It is defined as the act of intentionally debasing the quality of food offered for sale either by the admixture or substitution of inferior substances or by the removal of some valuable ingredient.
Food is declared adulterated if:
• A substance is added which depreciates or injuriously affects it,
• Cheaper or inferior substances are substituted wholly or in part.
• Any valuable or necessary constituent has been wholly or in part abstracted.
• It is an imitation.
• It is coloured or otherwise treated, to improve its appearance or if it contains any added substance injurious to health.
• For whatever reasons its quality is below the Standard
Adulterated food is dangerous because it may be toxic and can affect health and it could deprive nutrients essential for proper growth and development.
Now-a-days it is very common to hear or read news about the food items being adulterated and such products are being openly sold out and are consumed by people, which cause various health hazards. News has shown how milk and milk products are being adulterated with urea, soap and other hazardous chemicals .
Milk is defined as the clean, whole, fresh, lacteal secretion obtained by the complete milking of one or more healthy milk animals excluding that obtained within (15) days before or (5) days after the calving or such period as may be necessary to provide the milk practically colostrums free and containing the minimum prescribed percentage of sold not fat and milk fat .
Milk is a dynamically balanced mixture and a perishable food. It is one of few foods consumed in the natural form throughout the world. Milk contains 87% water, 3.3% protein, 3.9% fats, 5% lactose and 0.7% ash. Milk supply body with building protein, health giving vitamins, bone forming minerals, and energy supplying lactose and milk fat. Besides providing certain essential fatty acids it includes all essential amino acid. All the properties of milk make it an important food for adults, growing children, adolescents, invalid, convalescents and patients .
Milk is an important source of nutrients required for growth of infants and children and for health maintenance in adults. Milk is prefect food, readily digested and absorbed. It is chiefly valuable source of good quality fat, protein, carbohydrates, vitamins and minerals. Protein required for growth of infants and children. It is also required for maintenance of tissues in adults .
The extensive consumption of milk and dairy products makes these foodstuffs targets for more potential adulteration with financial gains for unscrupulous producers .
Adulteration of milk and other dairy products has existed from old times. That is why it was necessary to stipulate regulatory standards against adulteration in food and develop methods or tests to detect adulteration particularly adulteration of milk with cheaper and sometimes toxic chemicals is matter of serious concern .
Milk is adulterated either intentionally or accidentally during production and processing of milk. Harding et al. stated that there are many potential adulterants in liquid milk, such as neutralizers, salt, sugar, water, or solid contents. Borin et al. reported adulteration of powdered milk in Brazil and mentioned that the most frequent contaminants were starch, whey, and sucrose that range from 20-25%, which does not cause detectable flavor changes. But occasionally contaminant ratio may be as high as 60%. In Taiwan, the media showed that an adulteration ratio of 30% reconstituted milk in fresh milk has been found.
Normally the adulteration is done either for financial gain or lack of proper hygienic conditions of processing, storage, transportation and marketing. This ultimately leads to stage that the consumer is either cheated or often becomes victim of diseases. Adulteration is very common in developing countries. It is evenly important for the consumer to know the common adulterants and their effects .
One of the oldest and simplest forms of milk adulteration is through the addition of variable volumes of water to increase its volume for greater profit; this can substantially decrease the nutritional value of milk, and if the water added is contaminated there is a high risk to human health because of potential waterborne diseases . Sellers adulterate milk with water because it is cheap rather than starch which may be homogenized and obviously can be detected and discovered by the consumer (Adam. 2009).
In raw milk, chemical like formalin, hydrogen peroxide, boric acid and antibiotics are added to increase the shelf life .
The other kind of adulteration of milk by the additions of starch, rice flour, skim milk powder, reconstituted milk, urea, melamine, salt, glucose, vegetable oil, animal fat and whey powder. These additions is to increase the thickness and viscosity of the milk, and to maintain the composition of fat, carbohydrate and protein .
Some kinds of the adulteration, their impact on the health of human body are discussed in the following sections:
Water—————–
Water is the most common adulterant in milk . The major percentage of natural milk contains water (87%), but milk with added water is a serious concern. In one hand it decreases the nutritious value; on the other hand chemicals are added to compensate the density and colour after dilution with water. Since addition of water is the easiest way and cheap source for adulteration of milk.
Urea—————–
The common milk adulterant to increase the shelf life is addition of urea to milk,. Urea is also used to prepare synthetic milk and increase the SNF value. The average content of urea in cow milk is about 50 mg/100 ml (average). Urea content in milk may also increase due to unbalanced feeding of cows, . It is also used for heat stability . Health hazards associated are acidity, indigestion, ulcers and cancers. Urea is harmful to heart, liver and kidneys especially for kidneys as the kidneys have to do more work to remove urea from the body . This necessitates the importance of detection of urea in milk.
Hydrogen peroxide (H2O2)——————–
So to increase the shelf life, addition of chemical preservatives in branded milk is a very common practice. Sometimes hydrogen peroxide (H2O2) is used as a preservative . These additions have the potential to cause serious health-related problems.
Milk adulteration has been widely reported in developing countries such as Sudan, Pakistan, Brazil, India, and China
Methods for Detection of common adulterants in Milk and Milk Products————
(A) Milk
Tests which can be done at Home
S. No. Food Article Adulterant Method of detection Remarks
1 Milk Water The presence of water can be detected by putting a drop of milk on a polished slanting surface. The drop of pure milk flows slowly leaving a white trail behind it, whereas milk adulterated with water will flow immediately without leaving a mark.
2 Starch Add a few drops of tincture of Iodine or Iodine solution. Formation of blue colour indicates the presence of starch. Iodine solution is easily available in the medical stores
3
Urea
Take a teaspoon of milk in a test tube. Add half teaspoon of soybean or arhar powder, Mix up the contents thoroughly by shaking the test tube. After 5 minutes, dip a red litmus paper in it. Remove the paper after half a minute. A change in colour from red to blue indicates the presence of urea in the milk.
4 Detergent Shake 5-10 ml of sample with an equal amount of water. Lather indicates the presence of detergent
5 Synthetic milk Synthetic milk has bitter after taste, gives a soapy feeling on rubbing between the fingers and turns yellowish on heating Synthetic milk is made by adding while colour water
paint, oils, alkali, urea and detergent, etc.
6 Synthetic milk – test for protein The milk can be easily tested using Urease strips. Colour chart in Urease strips helps to arrive at the quantity of urea present in the milk.
Urease strip is a biostrip based on enzymatic assay.
7 Test for Glucose /Invert sugar Take a strip of Diacetric strip and dip in to the milk for 30 sec to 1 min. If the strip changes the color then it shows the sample of milk contains glucose .If there is no change in the color of the strip , then glucose is absent.
Glucose inverts sugar syrup is added to the milk increases the consistency and taste.
Tests which have to be done in Laboratory—————–
S. no Food Article Adulterant Method of detection Remarks
1
Vanaspati
Take 3 ml of milk in a test tube. Add 10 drops of Hydrochloric Acid. Mix one teaspoonful of sugar. After 5 minutes, examine the mixture. The red colouration indicates the presence of vanaspati in the milk
2 Formalin Take 10 ml of milk in a test tube and add 5 ml of concentrated Sulphuric acid from the sides of the wall without shaking. If a violet or blue ring appears at the intersection of two layers then it shows presence of formalin
Formalin enhances the life of milk and thus is added for preservation purpose.
3 Ammonium Sulphate •Take 5 ml of hot milk in a test tube. Add a suitable acid, eg., Citric Acid. The whey obtained is separated and filtered. Take the whey in another test tube and add 0.5 ml of 5% Barium Chloride. Appearance of precipitate indicates the presence of Ammonium Sulphate.
• Take 5 ml of milk in a test tube. Add 2.5 ml of 2% Sodium Hydroxide, 2.5 ml of 2% Sodium Hypochlorite and 2.5 ml of 5% Phenol Solution. Heat for 20 seconds in boiling water bath. If bluish colour turns to deep blue, it indicates the presence of Ammonium Sulphate. However, in case it turns pink, it shows that the sample is free from Ammonium Sulphate.
The presence of sulphate in milk increases the lactometer reading.
4 Salt Take 5 ml of Silver Nitrate reagent in a test tube. Add 2-3 drops of Potassium Dichromate Reagent. Add 1 ml of milk in the above test tube and mix thoroughly. If the contents of the test tube turn yellow, then milk contains salt. If it turns to chocolate colour or reddish brown, the milk sample is free from salt
Addition of salt in milk is mainly resorted to with the aim of increasing the corrected lactometer reading.
5 Hydrogen Peroxide • Take 5 ml milk in a test tube. Add 3 drops of Paraphenylene Diamine and shake well. Change in colour of the milk to blue confirms that the milk is adulterated with Hydrogen Peroxide,
Or
• To 10 ml of milk sample in a test tube add 10-15 drops of Vanadium Pentoxide reagent and mix. Pink or red colour indicates presence of Hydrogen Peroxide.
6 Sugar Take 3 ml of milk in a test tube. Add 2 ml of the hydrochloric acid. Heat the test tube after adding 50 mg of resorcinol, The red colouration indicates the use of sugar in the milk.
7 Sodium bi-carobonate / Neutralizer Take 3 ml of milk in a test tube and add 5 ml of rectified spirit to it. Then add 4 drops of rosalic acid solution. The appearance of red / rosy colouration indicates the presence of Sodium bi-carbonate in the milk.
8 Boric acid Take 3 ml of milk in a test tube. Add 20 drops of hydrochloric acid and shake the test tube or mix up the contents thoroughly. Dip a yellow paper- strip, and remove the same after 1 minute. A change in colour from yellow to red, followed by the change from red to green, by addition of one drop of ammonia solution, indicates that the boric acid is present in milk
To prepare the yellow paperstrip, dip Strips of filter paper in an aqueous solution of the turmeric, and dry it up.
9 Removal of Fat The Lactometer reading will go above 26. The milk will apparently
remain thick.
(B) Milk Products————-
Tests which have to be done at Home
S. no. Food Article Adulterant Method of detection
Remarks
1 Khoa and its products Starch Boil a small quantity of sample with some water, cool and add a products few drops of Iodine solution. Formation of blue colour indicates the presence of starch.
2 Chhena or Paneer Starch Boil a small quantity of sample
with some water, cool and add a
few drops of Iodine solution. Formation of blue colour indicates the presence of starch
.
Tests which have to be done in Laboratory——————
S. no Food Article Adulterant Method of detection Remarks
1 Sweet Curd Vanaspati Take 1 teaspoon full of curd in a test tube, Add 10 drops of hydrochloric acid. Mix up the contents shaking the test tube gently. After 5 minutes, examine the mixture. The red colouration indicates the presence of vanaspati in the curd.
2 Rabri Blotting paper Take a teaspoon of rabri in a test tube. Add 3 ml of hydrochloric acid and 3 ml of distilled water. Stir the content with a glass rod. Remove the rod and examine. Presence of fine fibres to the glass rod will indicate the presence of blotting paper in rabri.
3 Ghee, Cottage Cheese, Condensed Milk, Khoa, Milk Powder
etc., Coal Tar Dyes Add 5 ml of dilute Sulphuric Acid or concentrated Hydrochloric Acid to one teaspoon full of product sample in a test tube. Shake well. Pink colour (in case of dilute Sulphuric Acid) or crimson colour (in case of concentrated Hydrochloric Acid) indicates presence of coal tar dyes. If Hydrochloric Acid does not give colour, dilute it with water to get the colour to see the result.
4 Ghee Vanaspati or Margarine Take about one tea spoon full of melted sample of ghee with equal quantity of concentrated Hydrochloric acid in a test tube with stopper and add to it a pinch of sugar. Shake for one minute and let it stand for five minutes, Appearance of crimson colour in lower (acid layer) indicates presence of vanaspati or margarine.
• The test is specific for sesame oil which is compulsorily added to vanaspati and margarine.
• Some coal tar dyes also give a positive test.
• If the test is positive ie. Red colour develops only by adding Strong Hydrochloric acid (without adding crystals of sugar) then the sample is adulterated with coal tar dye. If the crimson or red colour develops after adding and shaking with Sugar, ensures presence of vanaspati or margarine only.
The high nutritional value of milk and its relative low cost compared with other protein sources has made it form a significant part of the diet of many populations worldwide. However, global increased demand has made milk prone to massive levels of fraudulent activity. Milk is a high-risk commodity of concern for fraudulent activities for financial gain whereby perpetrators may increase food safety hazards and diminish nutritional quality through intentional adulteration and/or malpractice under poor hygiene conditions, a lack of preservation, and no cooling facilities. Such types of fraud are becoming a common problem in many regions throughout the world, particularly in developing countries like India and Pakistan, which have largely unregulated practices. Milk used for human consumption can be adulterated with inferior, cheaper materials or hazardous chemicals, including pond water, reconstituted milk powder, cane sugar, urea, melamine, glucose, and detergents. Milk may be adulterated to such an extent that there is significantly less nutritional value and it may also be toxic for public health, as shown in recent milk fraud scandals. Thus, more analysis is essential to generate awareness among the public about malpractices or negligence in milk production. Also the consumer must be aware about the kind of milk he consumes, and the authorities should realize the importance of frequent inspection of the market to check whether this milk meets the minimum legal standards.
