Q. Basic tests for milk analysis?
The Federation R&D has developed these tests stepwise and these should be done in the same sequence along with the blank, good milk. Let us learn about these tests.
Taste Flavour and Appearance
Milk should have its own mild sweet flavour. A soapy or chemical flavour and slight pale colour or extra white colour may give indication regarding adulteration. Rancid flavours in milk are also easily detectable through perception of smell.
Milk pH
Milk has a pH between 6.6 to 6.8. The pH of the given sample of milk can be tested by pH strip prepared with phenol red, which gives a change in colour exactly at pH 7.0. Thus this strip is sensitive to even slight levels of neutralization.
Alcohol Test
Alcohol test is based on the principle of curdling of milk in presence of alcohol. This forms the principle for testing of synthetic milk, which is composed of neutralizers, stabilizers and detergents. Take 0.5 ml of milk sample in a test tube along with a blank (sample of a good milk).
Add to each tube 0.5 ml of 95% alcohol, mix, heat and observe for clotting.
Presence of Additives
The additives such as starch, urea, sugar and soda are added to milk to maintain its colour, flavour, sweetness and pH. For the analysis of these adulterants, standard methods are used. These are highlighted herewith:
For Starch: Iodine test is used.
For Soda: Rosalic acid test is used for determination of added soda.
For Sugar: Resorcinol test is used for determination of sugar.
For Urea: Dimethyl amino benzaldehyde test is used for urea determination.