Milk Adulteration and Detection Techniques
Anamika Sahu, Nutan Chauhan
Veterinary Public Health and Epidemiology Division
ICAR- Indian Veterinary Research Institute, Bareilly, Uttar Pradesh
anamikasahu1992@gmail.com
Milk is considered as the ‘best and complete food’ because it is rich in nutrients which are required by both infants and adults. It is one of the good sources of protein, fat, carbohydrate, minerals and vitamin that is required for a healthy body. Unfortunately, milk is being quite easily adulterated all over the world. Possible reasons might be due to – high nutritional value, demand and supply difference, highly perishable nature, limited purchasing potential of customers and lack of suitable detection tests. Milk adulteration is the most common fraudulent practice done by the developing countries to mask the quality parameter such as fat and protein and to increase the shelf life of the milk which leads to serious health risks to consumers life. Milk adulteration includes the dilution or addition of inexpensive, low quality or hazards products like edible agents (sugar, starch, glucose), chemicals (formalin, urea), preservatives (Hydrogen peroxide) and coloring agents (annatto, coal tar dye). Detection of adulterated milk can be done by chemical qualitative methods which is an affordable, convenient and easy to perform like rapid platform test and quantitative methods that is complex and diverse but accuracy is more.
Qualitative detection of adulterants in milk
Adulteration of milk with edible agents |
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Adulterant |
Test |
Interpretation |
Sugar |
5 mL milk sample, add 1 mL conc. HCl and 0.1 g resorcinol solution and keepit in water bath for 5 min |
Red color indicates the presence of sugar |
Starch |
Boil 3 mL of milk sample, cool it and add 1 drop of 1% iodine solution |
Blue color indicates the presence of starch |
Glucose |
Heat the mixture of 1ml of milk sample with 1ml of modified Barfoed’s reagent for 3 min in water bath after that rapidly cool under tap water |
Deep blue color indicates the presence of glucose |
Common salt |
5 ml of milk sample with 1 ml of 0.1 N silver nitrate solution. Mix it and add 0.5 ml of 10% potassium chromate solution |
Yellow color indicates the presence of added salts |
Buffalo milk |
Dilute the milk 1/10 and a drop of it on the glass slide. Now place a drop of Hansa test serum on the drop of milk and mix together with a glass rod. |
Curd like clot develop within a minute in milk containing buffalo milk |
| Water | Test for detection of nitrate in milk by using 1ml of diphenylamine with 100ml of sulphuric acid poured slowly through the side of test tube of 5ml milk samples | Presence of blue colour indicates presence of water |
| Adulteration of milk with different harmful chemicals | ||||
| Hydrogen peroxide | Add to 5 mL of milk sample with an equal volume of raw milk and 5 drops of 2% solution of paraphenylenediamine | Blue color indicates the presence of hydrogen peroxide as an adulterant | ||
| Formalin | Take 10 mL milk sample and add 5 mL conc. sulfuric acid with a little amount of ferric chloride without shaking | Violet or blue color at the junction of two liquid layers indicates the presence of formalin | ||
| Ammonium sulfate | Take 2 ml milk with add 0.5 ml NaOH 0.5 ml sodium hypochlorite (2%) and 0.5 ml phenol (5%) and keep in boiling water bath for 20 sec | Bluish colour observed which turns deep blue afterward. Pure milk shows pink colour which gradually changes to bluish | ||
| Urea | 5 ml milk in a test tube, add 0.2 ml urease (20 mg/m) and shake it by adding 0.1 ml Bromothymol Blue (BTB) solution | Blue colour indicates the presence of urea in milk | ||
| Detergent | 5 ml milk sample add with 0.1 ml 0.5% Bromocresol Purple (BCP) solution | Violet colour indicates the presence of detergent | ||
| Nitrate | Mix 10 ml sample milk with 10 ml of mercuric chloride solution, filter it and take 1 ml filtrateand add 4 ml of diphenyl amine sulphate or diphenylbenzidine reagent | Blue colour indicates the presence of nitrates. | ||
| Borax and boric acid | 5 mL milk sample and add 1 mL conc. HCl to it. A turmeric paper is dipped and dried | If the turmeric paper turns red, it indicates the presence of borax or boric acid | ||
| Adulteration of milk with colouring agent | ||||
| Annatto | Ether ia added to 10ml of milk after shaking, allowed to stand for few minutes | Yellow colour indicates presence of annatto | ||
| Coal-tar dye | 5ml milk in with equal conc. HCl is added | Pink colour indicates presence of coal tar dye | ||
Quantitative detection of adulterants in milk
Quantitative detection techniques are rapid, sensitive, accurate which is mostly used in developed countries and type of detection techniques depend on the nature of adulterants in milk.
| Techniques | Detection |
| Liquid Chromatography (LC) and Enzyme Linked Immunosorbent Assay(ELISA) | Foreign protein |
| Polymerase Chain Reaction (PCR) and Polyacrylamide Gel Electrophoresis (PAGE) | Adulteration of milk of a different species |
| Surface Enhanced Raman Spectroscopy (SERS) | Melaminne |
Milk is the important source of energy, so it is important to identify the adulterated milk using a qualitative and quantitative methods by which we can prevent the many fatal disease caused by taking adulterated milk. So paper tries to collect few important detection techniques of adulterated milk.
Qualitative detection of adulterants in milk
