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Adulteration of Milk: A Drop of Black in White

milk adulteration

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The words adultery and adulteration sound similar and are from a common original word…..both these facts are true!!!! They are similar in meaning to the extent that they imply moral and ethical compromise.

Ancient times have records to show that both were treated as heinous crimes with public beheading as the given punishment. Food adulteration is truly the lowest form of “Food Practice” as it can cause grievous injury to health and can even be fatal.

Milk may be defined as the whole, fresh, clean lacteal secretion obtained by the complete milking of one or more healthy milch animals, excluding that obtained within 15 days before or 5 days after calving and containing the minimum prescribed percentage of milk fat and solids-not fat.

This bookish definition needs to be known by the reader to understand two things….first that milk is an almost ideal food and second it certainly is the easiest to adulterate and corrupt in quality.

It has high nutritive value and supplies bodybuilding proteins, bone-forming minerals, and health-giving vitamins, and furnishes with energy-giving lactose and milk fat.

It contains the above nutrients in an easily available and utilizable form. All these properties make milk an important food for expectant mothers, growing children, adolescents, adults, the elderly, and even patients. Notably, it is the first food that we consume after birth.

Milk is not a single profile solution but a kind of emulsion that has numerous suspended solids in it. It is thus possible to alter the composition as long as physical qualities are seemingly normal.

These include color, pouring consistency, smell, and even taste to some extent. The consumer, in reality, has not many means of judging the conditions under which the milk has been produced, and additionally, he is not qualified to judge if the product is free from adulteration or contamination.

Attention will, however, be directed towards those problems of health, cleanliness, and keeping quality of the product, which must be taken into account to ensure a wholesome and safe milk supply. In the case of milk and milk products, the qualities or attributes, which need to be spotlighted are the following:

  • Physical Quality: The flavor and appearance of the product, normally judged by a seller with a great amount of firsthand experience.
  • Analytical Quality: Standard tests are used to ascertain physical, chemical, biochemical, and rheological (viscosity and textural) profiles and hence, the quality of milk.
  • Microbial Quality: These tests are essential for knowing the hygienic standards maintained in a dairy plant. Microbiological quality has a direct impact on the safety of milk consumption.

Subsequently, it is highly contaminated by man and his practices and the prevailing environment. Milk being highly nutritious is also susceptible to microbial spoilage and disease-causing contamination.

The production practices applied in many developing countries may not be as sophisticated as those adopted in advanced countries.

To safeguard the milk delivered at the dairy dock, hygienic handling at farm level, maintenance of milk animals and their nutrition, hygienic milking practices, and subsequent storage are some of the main areas of concern and efforts should be made to protect the possible type of contamination.

The low availability of milk is due to the poor breeds of milch animals, maintained by inadequate feeding, management, and health care.

This indicates that there is a short supply of milk, consequently, prices of milk are truly high. Due to this milk is becoming a “luxury item” and somewhat out of reach of common consumers. It is to the above-said factors that there is every likelihood of milk being adulterated in order to meet the increasing demands and naturally to fetch greater profits.

Adulteration implies to corrupt, debase or make appear improved by a mixture of a foreign or an inferior substance, especially for sale Adulteration in milk and milk products, is one of the most challenging areas the food industry is facing today, which needs an urgent solution today. Milk may be regarded as a unique commodity that can be very easily adulterated and marketed without the adulteration being detected in most of the cases. The various forms of adulteration are;

  • Addition of water
  • Skimming or removal of fat
  • Addition of skim milk
  • Addition of some soluble solid substance like (a) Starch (b) Sugar (c) Skim milk powder (d) Salt
  • Addition of coloring matter like (a) Annatto color (b) Coal tar dyes etc.
  • Addition ofpreservatives like (a) Formalin (b) Hydrogen peroxide (c) Hypochlorites
  • Addition of neutralizers like Sodium carbonate or sodium bicarbonate.
  • Addition of fertilizers like (a) Ammonium sulphate (b) Potassium nitrate (c) Urea
  • Addition of buffalo milk to cow milk.
  • Accidental adulterations in milk include the entrance of (a) Dirty water (b) Alkalis from detergent (c) Vegetable oil (d) Household dust and dirt (e) Dung

The addition of water, removal of fat, and addition of skim milk is done to increase the volume of milk and to derive an extra profit from a given volume of milk as mentioned earlier. This form of adulteration can be detected by specific gravity and fat test.

Addition of water and some soluble solid substances like starch and skim milk powder is carried out to restore the consistency, viscosity, and total solids content. Coloring matter is added to milk to make up the color losses caused by partial skimming and dilution of milk.

Preservatives are added generally to milk to check the growth or to destroy the microorganisms present in milk and to prolong its keeping quality.

Neutralizers are added to milk to reduce the acidity of milk. Fertilizers may also be added to achieve the usual S.N.F. values. As all these practices are not permissible, a study of various forms of adulteration in a locality may be of great help in safeguarding and improving the quality of market milk in the concerned area.

Methylene blue dye reduction test (MBRT) is commonly employed to assess the microbiological quality of raw and pasteurized milk. If the milk samples are contaminated, then the blue color of the dye is reduced to white. It is inferred that sooner the de-colorization, the more inferior is the bacteriological quality of milk. The microbial contamination can also be assessed using the Resazurin test. The blue color of the dye is reduced to various degrees viz. mauve, purple, pink and colorless depending upon the contamination.

Adulteration of milk samples can be detected by employing various methods. The presence of common table sugar in milk can be detected by checking the density of the sample with lactometer. The addition of sucrose increases the density than the normal levels. Another way to detect the presence of sucrose is by testing the sample with resorcinol. Ketose sugars give a red precipitate with resorcinol.

It is a very common practice followed to add starch to the milk to increase its viscosity. Presence of starch can be easily detected with the help of iodine solution. A blue coloration indicates an adulterated milk sample.

Generally, acids like benzoic acid and salicylic acid are added to milk to increase its shelf life. The presence of these acids can be detected by adding concentrated sulphuric acid and ferric chloride. These react with benzoic acid and salicylic acid to give buff-colored and violet-colored reaction products.

Soap is added to milk to increase the foaming and to have a thicker consistency. Addition of such chemicals adversely affects the health and results in ailments especially related to the stomach and kidneys. Soap can be detected by adding phenolphthalein indicator to the adulterated milk. A pink color will be observed if the soap is present.

Formalin is a preservative and can preserve milk for a long period of time. However, it is highly toxic and is responsible for causing liver and kidney damage. Formalin reacts with Sulphuric acid and ferric chloride to give a purple-colored ring at the junction of the milk layers, thereby indicating the presence of formalin adulterated in milk.

Ammonium sulphate is added to the milk as it increases the lactometer reading by maintaining the density of milk.  Ammonium sulphate can be detected by adding sodium hydroxide, sodium hypochlorite, and phenol, the reaction of the three reagents with ammonium sulphate results in the formation of deep blue color.

The interesting fact remains that all these tests are very simple to carry out and easy to understand. The results obtained are accurate. They do not need sophisticated instruments or intricate methodology. Hence, they are known as Platform Tests. (Platform implies tabletop)

The increasing population and consequently greater demand for milk are making quality milk rather difficult and out of reach. A common complaint on the part of consumers in general and housewives, in particular, is that it does not meet the quality according to the prices demanded. It is felt at this juncture that certain moral and legal standards should be implemented through government or allied agencies if the quality is important. At any cost, the quality of milk is directly related to public health and their wellbeing. Serious problems of epidemics and outbreaks of poisonings may be greatly reduced through the proper functioning of such government agencies.

Summing up, what should an alert and enlightened consumer do to prevent this major social evil? First and foremost, he should educate himself about the science of milk adulteration. Furthermore, every individual must be completely in the know of his fundamental legal rights. He should be very discerning and choosy as to his food purchases….brands, labels, accreditations, and nutritional content should govern his decision to buy. Only then, in keeping with the demand and supply equation would we be able to put at rest this black drop in the white ocean….Adulteration of Milk.

References: –

  1. Common milk adulteration and their detection techniques. Tanzania Azaand Supply equation, we together can d and Shoeb Ahmed, International Journal of Food Contamination 3(1)Article number: 22.December 2016.
  2. Detection of adulteration in milk and some dairy products. Saadia et al.Assiut Veternary Medical Journal. Vol. 64 No. 157 April 2018, 1-10
  3. Detection of Adulteration in Milk and Milk Products– Present Status.Rajan Sharma , Y.S Rajput and Bimlesh Mann.ICAR- National Dairy Research Institute, Karnal
  4. A Study on Detection of Adulteration in Milk Samples from Different Regions of Thuraiyur District in Tamil Nadu, India. Brindha* , P. Chitra, R. Janarthanan and A. Murali.International Journal of Current Microbiology and Applied Sciences. Volume 6 Number 12 (2017) pp. 3303-3310
  5. Analysis of milk quality, adulteration and mastitis in milk samples collected from different regions of Dehradun.Shrishti Nirwal, Rakesh Pant and Nishant Rai J. of PharmTech Res. 5(2): 359-364. 2013.

Also read : Adulteration :The underbelly of food processing

Jyoti D Vora

MSc., PhD, F.S.Sc. , MASFFBC, CME (USA), Net Cleared, Certified Functional Foods Scientist, (FFC, USA), Proprietor and CEO, Dhirang Consultants, Mumbai.


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