Detect various adulterants present in milk

Requirements: Milk, test tube, beaker, and test tube stand etc.

Theory: Quality control tests for milk are very important to assure adulterant free milk for consumption. Adulteration of milk reduces the quality of milk and can even make it heazardous. Adulteration like soap, acid, starch, table sugar and chemical like formalin may be added to milk. Most of the chemicals used for as adulterates are poisonous and cause health hazards. 

Adulterats are mainly added to increase the shelf life of milk. Some of the preservatives like acid and formalin are added to the milk as adulterants, thereby increasing the storage period of milk. Generally water is added to the milk to increase the volume content of the milk. Some of them common adulterants found in the milk are as micro-organism, table sugar, starch, acid, soap, formalin, ammonium sulphate, urea etc.

Procedure: 

Detection of miroorganism in milk

Measure out 5 mL milk into test tube and 2 drops of methylene blue indicator is added into it. Mix the content of test tube well. A blue colour is observed. The test tube now kept in an incubator at 37.c for 30 minutes. After incubation, if the colour changes from blue to white in a short period of time, indicates the presence of bacteria in milk.

Detection of table sugar in Milk

Measure out 5 mL milk into test tube and 2 mL of conc. HCl is added to the test tube. The content is mixed well and then 0.1 g of resorcinol powder is added to the test tube. Mix the content in the test tube. Now the test tube is placed in a boiling water bath for 5 minutes. After the incubation if red colour is observed,indicateds the presence of table sugar in milk.

Detection of starch in Milk

Measure 2 mL of milk in test tube. The test tube is then kept for incubation in boiling water bath for5 minutes. After incubation, the test is cooled and few drop 1% iodine solution and mix thr content well. Appearance of blue colour indicates presence of starch in milk.

Detection of acid in Milk

Measure out 5 mL milk into test tube and. Add few drops of Conc. Sulphuric acid and gently shake the test tube. Add 0.5% ferric chloride solution dropwise into the test tube. Mix the content well. Development of buff colour indicates the presence of benzoic acid and if violet colour is observed shows the presence of salicylic acid.

Detection of soap in Milk

Measure out 5 mL milk into test tube and. Add 5 mL of hot water into the test tube containing milk. Now adds 1-2drops of phenolphthalein indicator solution into test tube. Mix the content of test tube. Development of pink colour confirms the presence of soap in milk.

Detection of formalin in Milk

Measure out 2 mL milk into test tube and. Add 2 mL of 90% sulphuric acid and ferric chloride mixture into the test tube. Formation of purple colour ring at theinterface of two layers indicates the presence of formalin in milk.

Detection of ammonium sulphate in Milk

Measure out 2 mL milk into test tube. Add 0.1 mL of 2% sodium hydroxide into the test tube. Mix the contents well. Add 0.1 mL of 2% sodium hypochloride solution into the test tube. Finally add 0.1mL of 5% phenol into the test tube. Mix the content well. A light blue colour will be observed on mixing. Keep the test tube in a boliling water bath for 20 secconds. Formation of deep blue colour indicates the presence of ammonium sulphate in milk.

Test for detection of urea in Milk

Measure out 5 mL milk into test tube and mixed with 5 mL of paradimethyl amino benzaldehyde (16%). If the solution turns yellow in colour, confirm the presence of urea in milk.

Result: In the given urine sample no abnormal constituents (protein, sugar, mucus, ketone body etc.) are present.