Peroxide value

peroxide value as per IP

1. Peroxide value

2. Peroxide value It is the number of milli equivalents of active oxygen that expresses the amount of peroxide contained in 1000 g of the substance.

3. Procedure -IP Weight unless otherwise mentioned in the individual monograph . Weigh 5 g of the substance being examined, a ccurately weighed into a 250ml glass stoppered conical flask, add 30ml of a mixture of 3 volumes of glacial acetic acid and 2 volumes of chloroform swirl until dissolved and add 0.5 ml of saturated potassium iodide solution.

4. Allow to stand for exactly one minute with occassional shaking add 30 ml of water and titrate gradually with continious and vigorous shaking, with 0.01M sodium thio sulphate until yellow colour almost disappears. Add 0.5 ml of starch solution and continue the titration shaking vigorously until the blue colour just disappear [ a ml]

5. Repeat the operation omitting the substance being examined [ b ml]. The volume of 0.01M sodium thio sulphate in the blank determination must not exceed 0.1 ml

6. Calculation Peroxide value = 10 ( a-b) /w Where w = weight in g of the substance

7. Autoxidation The process of oxidation induced by air at room temperature referred to as “autoxidation”.

8. Rancidity Rancidity is a term generally used to denote unpleasant odours and flavours in foods resulting from deterioration in the fat or oil portion of a food. There are two basic types or causes of rancidity that cause and/or contribute to the degradation of stored edible oils: oxidative and hydrolytic Oxidative rancidity, known as autoxidation, occurs when oxygen is absorbed from the environment

9. Hydrolytic rancidity, also called hydrolysis or enzymatic oxidation, occurs in the absence of air, but with moisture present. Enzymes found naturally in plant oils (i.e., lipoxygenase, cyclooxygenase) and animal fats (i.e., lipase) can catalyze reactions between water and oil Microbial rancidity, in which micro-organisms such as bacteria, molds and yeast use their enzymes to break down chemical structures in the oil, producing unwanted odors and flavors. Water needs to be present for microbial growth to occur.