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.