Milk Adulteration and Its Toxicological Effects



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Despite the governing the control of quality and sale of milk existing for decades, adulteration of milk could not be checked. With the increase demand of milk, the adulteration of this commodity is on increasing day by day. The problem of adulteration is more during summer and rainy seasons, when milk production in comparatively much less than the winter season.

Adulteration of a food article may be defined as making the article impure by the addition of some of the legally prohibited substances into a more valuable product or the subtraction into a more valuable component a product to devalue the latter or the combination of both, with a view to increase the bulk or quality and to increase unlawful, excessive profit through sale of such a food.

Ever since the system of organized milk collection was introduced in this country, the quality of milk received by our dairy industry has not been improved. The adulteration is carried out through a number of fraudulent practices, which not only lower down the nutritional value but makes it unfit for human consumption with toxic effects. The adulterated milk also leads to the production of standard dairy products resulting in economic losses. The practice of adulteration has become extensive due to existing conditions of production and handling of milk. Various no. of tests determine the nature and extent of adulteration of milk and even adulterants.

The purchasing power of many consumers in our country is very low. Consequently such consumers often go for the lower price of milk, even knowing about the poorer quality of the same. Such attitude of the consumers makes adulteration of milk possible to a greater extent. [1]

Types of adulteration

The commonly used adulterants are

Addition of water.
Addition of separated milk.
Addition of thickening agents when milk id watered it becomes deficient in density and also viscosity which may be restored by addition of substances like gelatin, cane sugar, starch, glucose.
Partial skimming.
Addition of coloring matter to restore color lost by skimming or diluting or to make naturally poor looking to appear rich.
Unusual adulterants-of late, due to more wide spread use of fertilizers by farmers in India, who are also the primary milk producers, a few new types of adulterants like urea, ammonium sulphate etc. have come up. [2]


Milk is an emulsion or colloid of butterfat globules with in a water based fluid that contains dissolved carbohydrates and protein aggregates with minerals. Milk is the secretion, practically free from colostrum, obtained by the milking of healthy represents one of the sources of essential amino acids for human nutrition. These nutritional attributes of milk have long made it a mainstay particularly in the diet of growing children. There are estimated to be the 8 to 10 thousand milk products made of milk available in world thus making it exceptionally versatile raw product.

Milk is composed of water, fat, protein, lactose, and minerals. The concentration of these products varies between cows and breeds. Total milk solid refers specifically to fat, protein, lactose and minerals. This is to be differentiated from SNF (solid not fat), a frequently used term which describes the total solid contents minus fat.

The nutritional as well as economic value depends upon its solid contents. The higher the solid content the greater the milk product yields. Cheese yield are directly relayed to milk casein content. Milk contains dozens of other types of proteins beside the caseins including enzymes. These other proteins are more water-soluble than the caseins and do not form larger structures. Because the proteins remain suspended in the whey left behind when the caseins coagulate into curds, they are collectively known as whey proteins.

Calcium, phosphate, magnesium, sodium, potassium, citrate, and chlorine are all included as minerals and they typically occur at concentration of 5–40 mm. [3]

Composition off milk

Water – 84-90%

Fat – 2-6%

Protein – 3-4%

Lactose – 4-5%

Ash – .1%


A multitude of events takes place in the process of delivering milk from the farm to the dinner table and all are designed to provide the consumer with wholesome, nutritious and safe products. The production of quality milk and milk products are begins in the farms and continuous through further handling, processing and distribution.

Milk processing has two primary objectives:

Destruction of human pathogens through pasteurization.
Keeping the quality and shelf life of the products without significant loss of flavor, appearance, physical and nutritive properties.

Milk processing and plant procedure seeks to:

Prevent further bacterial contamination of raw material.
Reduce bacterial numbers in milk.
Protect the finished products from recontamination through careful handling, proper packing and storage.

Pasteurization is the means whereby raw milk is rendered safe for human consumption. It is the process of heating milk to a sufficient temperature for a sufficient length of time to make it free from pathogens, and spoilage bacteria. [4]



Formalin is added in milk to preserve it for longer period. Formalin is very toxic. Many cases of biological mutation and reproduction complication have been noted. On toxicity it causes tumors formalin causes CNS disorders and also irritates nose, throat and lungs. When taken in high dose it cause cancer and may lead to coma.


Urea is generally added in the preparation of synthetic milk to raise the SNF value. Potential symptoms are burning sensation in throat and chest; cough, dyspnea, exercise-induced asthma (one case); redness, in eyes and skin, headache; nausea, vomiting, lung damage-fibrosis, inflammation (HE11). Affected organs are respiratory system, skin, eyes, it has also used medically as an abortifacient and a skin moisturizer.


The presence of ammonium sulphate increases the lactometer reading. The product has low toxicity. However, the following points should be noted. On skin contact prolonged contact may cause some irritation. On eye contact it may cause irritation. On ingestion small quantities are unlikely to cause toxic effect and large quantities give rise to gastro-intestinal disorders. On inhalation high dust concentration of air-borne material may cause irritation of the nose and upper respiratory tract with symptoms such as sore throat and coughing. Inhalation of some decomposition gases may cause irritation and corrosive effects on the respiratory system. Some lungs effect may be delayed.


Milk is treated with different concentrations of hydrogen peroxide (0.01, 0.02, 0.03, 0.04, 0.05 and 0.06 % of H2O2), along with control sample (untreated sample), for the purpose to activate Lacto peroxidase system, which destroy the bacterial population by its antibacterial effect. Lacto peroxidase (LP) system is naturally present in raw milk that prevents the bacterial multiplication due to its bacteriostatic effect. By activating the LP-system, shelf life of milk can be increased for 8 to 12 hours. Lacto peroxidase (LP) system consists of three components; LP, thiocyanate and hydrogen peroxide. And it is active only when all of three components are present. Lacto peroxidase catalyzes the oxidation of thiocyanate by hydrogen peroxides and generates an intermediate product with antibacterial properties. These products have a broad range of antimicrobial effects against bacteria, fungi and viruses.


Raw milk preservation by use of H2O2 is done for many important purposes like;

To enhance the shelf life of milk for consumption without microbial contamination.
To minimize the processing cost by heating the milk.

Side Effects of Hydrogen Peroxide

Eye exposure to dilute hydrogen peroxide may cause extreme irritation and pain, but is unlikely to cause permanent damage.
Enemas of dilute hydrogen peroxide have been reported to cause serious gastrointestinal side effects.
Skin contact with concentrated hydrogen peroxide can cause severe burns and even gangrene.
An overuse of H2O2 can cause damage to DNA cells, and prevent them from replicating, hence leading to premature aging.
The use of hydrogen peroxide can cause your skin to dry out or rather drains away the moisture content in skin, which is required to keep your skin looking young and supple.
Vitiligo is a disease that is marked by the loss of skin pigment, which affects a lot of people. Studies show that it is due to the high levels of hydrogen peroxide in the blood and epidermis.
It can cause irritation in gums and teeth, since H2O2 is a highly reactive compound.
Hydrogen peroxide being highly reactive can easily pass through your tooth’s enamel and react with the dentin and pulp part of your tooth.
Throat soreness is another common side effect of hydrogen peroxide. [5]


The common sugar present in milk is lactose. The fat content of the milk is more compared to the protein content. Table sugar like sucrose is added to the milk to increase the carbohydrate content of the milk and thus the density of milk will be increased. So the milk can now be adulterated with water and it will not be detected during the lactometer test. Ketose sugar will react with the resorcinol to give a red colored precipitate, indicating the presence of Table sugar in milk.


Sugar can suppress your immune system.
Sugar eaten during pregnancy and lactation can influence muscle force production in offspring, which can affect an individual’s ability to exercise.
Sugar can elevate glucose and insulin responses and return them to fasting levels slower in oral contraceptive users.
Sugar can increase reactive oxygen species (ROS), which can damage cells and tissues.
Sugar can cause hyperactivity, anxiety, inability to concentrate and crankiness in children.
Sugar can produce a significant rise in triglycerides.
Sugar causes a decline in tissue elasticity and function – the more sugar you eat, the more elasticity and function you lose.
Sugar reduces high-density lipoproteins (HDL).
Sugar can lead to ovarian cancer.
Sugar can increase fasting levels of glucose.
Sugar causes copper deficiency.
Sugar can make tendons more brittle.
Sugar can increase the levels of glucose in the blood much higher than complex carbohydrates in a glucose tolerance test can.
Sugar can cause two blood proteins – albumin and lipoproteins – to function less effectively, which may reduce the body’s ability to handle fat and cholesterol.
Sugar can contribute to Alzheimer’s disease.
Sugar can cause platelet adhesiveness, which causes blood clots.
Sugar can cause hormonal imbalance – some hormones become underactive and others become overactive.
Sugar can cause free radicals and oxidative stress.
Sugar increases the concentration of bile acids in stool and bacterial enzymes in the colon, which can modify bile to produce cancer-causing compounds and colon cancer.
Sugar combines with and destroys phosphatase, a digestive enzyme, which makes digestion more difficult and can aggravate premenstrual syndrome (PMS).[6]


Addition of salt in milk is mainly restored with the aim of increasing the corrected lactometer reading. All four cationic electrolytes (sodium, potassium, magnesium, and calcium) are available in unrefined salt, as are other vital minerals needed for optimal bodily function. Too much or too little salt in the diet can lead to muscle cramps, dizziness, or even an electrolyte disturbance, which can cause neurological problems.

Excess salt consumption has been linked to:

Exercise – induced asthma.
Gastric cancer is associated with high level of sodium.
Left ventricular hypertrophy (cardiac enlargement).
Duodenal ulcer. [7]

Vegetable Fat

Milk fat is the natural source of variable variety of fatty acids diversified in nature. It is separated to make the cream and sold at high prices. People separate the cream from the milk and add vegetable fat into the milk and then sell it after homogenization. Vegetable fat is unsaturated and it gets oxidized and becomes rancid when exposed to air so become hepato-toxic and may cause liver cirrhosis. Small milk globules become rancid when oil and vegetable fat is being added and interesting thing is that color and consistency of the milk remains normal. [8]


Milk contains relatively large amount of fat. Addition of carbohydrate to milk increases its solid content. There by reducing the amount of fat present in the milk. Starch is one such component that is added to adulterate milk. The test to detect starch in milk uses iodine solution, addition of which turns the milk solution to blue black color due to the formation of starch Iodo complex, in the presence of starch.

Potential symptoms are irritation of eyes, skin, mucous, membranes, rhinorrhea, cough, chest pain, dermatitis.


Soap is added to milk to increase the foaming of milk and thus to have thick milk. Addition of such chemicals will cause health problem especially related to stomach and kidneys. Soap can be detected by adding phenolphthalein indicator to the adulterated milk. A pink color will be observed if soap is present as the alkali will be neutralized by the acidity of the milk when phenolphthalein indicator is added. [9]


The new Neutralizers Test manufactured by Astori Tecnica allows the immediate colorimetric determination of the presence of added neutralizers (such as NaOH, KOH, carbonates, bicarbonates, ammonia, various alkalis, etc.) in milk or cream. These prohibited substances may be added to fresh or badly preserved milk with the tricky purpose to correct its pH and acidity values to optimal ones, and so pretend the milk is freshly milked or perfectly preserved. [10]


” Research Can Lead To Longer Shelf Life For Dairy Products “(http: // /2002/12/021223084204.htm) 2002-12-23. Retrieved 2010-08-28.
Detect Adulteration in Milk: Empowering Consumers to Test Themselves (
Henriksen J, (2009) “Milk for Health and Wealth”. (ftp: //ftp. fao. org/doc rep/fao/011/i 0521e/i 0521e00.pdf) FA O Di versification Booklet Series 6, Rome.
Schultz, Madeline (April 2012) fluid milk profile (http: //www. products/lives tock/dairy/fluid-milk-profile/). Iowa State University.
T. Matsuoka (2004). Detection of adulterants in milk using near infrared spectroscopy. J. Food Sci. Tech. 41(3): 313-316.
Borin, A., M. F. Ferrao, C. Mello, D. A. Maretto and R. J. Poppi (2006). Least-squares support vector machines and near infrared spectroscopy for quantification of common adulterants in powdered milk. Analytica Chimica Acta. 579:25-32.
Tipu, M. S., I. Altaf, M. Ashfaq, S. Siddique (2007). Monitoring of chemical adulterants and hygienic status of market milk. Handbook published by Quality Control Laboratory, Lahore, Pakistan. pp.: 7.
Jha, S. N. And T. Matsuoka (2004). Detection of adulterants in milk using near infrared spectroscopy. J. Food Sci. Tech. 41(3): 313-316.
Sengar, M. S. (2007). Milk adulteration on rise in Agra. Friday, November, 07, India. Accessed from
Anonymous, (2012). Introduction to dairy science and technology: milk history, consumption, production, and composition. International Dairy Federation, Bulletin 423/2007. Accessed from: http://www.foodsci. cuoguelph. ca/dairyedu/intro.html.

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