Milk adulteration and detection techniques

October 1, 2020

1429

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
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.