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,
accurately 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

10. • 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.