Q. Determine the peroxide value in the of fat?
After undertaking this activity, you will be able to:
• determine the peroxide value in a given sample of fats/oils, and
• check whether any given samples of oils/fats conforms to the standard.
Principle
The peroxide value is a measure of the peroxides contained in a sample of fat expressed as milli-equivalents of peroxide per 1000 grams of the material. The material in an acetic acid-chloroform medium, is treated with an aqueous solution of potassium iodide. The liberated iodine is titrated with the standard sodium thiosulphate solution.
Materials Required
Reagents
Acetic acid-chloroform solution - Mix three parts by volume of glacial acetic acid with 2 parts by volume of chloroform
Saturated potassium iodide solution
Sodium thiosulphate solution- 0.1 N
Starch solution (1%)
Apparatus
Pipette 1ml capacity
Conical flask
Procedure
Carry out the experiment following the procedure given herewith:
1) Weigh approximately 5 g of the sample of fat in a 250 ml conical flask.
2) Add 30 ml of the acetic acid-chloroform solution.
3) Swirl flask until the sample is dissolved.
4) Add 0.5 ml of the saturated potassium iodide solution.
5) Allow the flask to stand exactly one minute with occasional shaking and then add 30 ml distilled water.
6) Titrate with 0.1 N sodium thiosulphate solution with constant and vigorous shaking.
7) Continue the titration until the yellow colour almost disappears.
8) Add 0.5 ml of the starch solution and continue the titration until the blue colour just disappears.
9) Conduct a blank determination of the process in the same manner as described in steps 2-8. Here, we start with acetic acid- chloroform solution only. No fat sample is added.