The document discusses various chemical properties of lipids including iodine value and peroxide value. Iodine value measures the degree of unsaturation in oils and fats, with higher values indicating more double bonds. It is determined by reacting lipids with iodine and titrating excess iodine. Peroxide value measures peroxide content as a sign of oxidation, determined by titrating peroxides with thiosulfate. The document also summarizes common iodine and peroxide values of various oils and fats, and discusses factors that influence lipid oxidation. A research study is summarized that examined effects of blending different oils on storage stability and sensory properties of an extruded snack.

1. CHEMICAL PROPERTIES OF
LIPIDS
Anchal Awana
B.Tech Food Technology
Section – A
Roll no - 18

2. IODINE VALUE
It is the number of grams of iodine
or iodine compound absorbed by 100g
of oil/fat .

3. Objectives:-
 It is direct representation of the degree
of unsaturation of the oil /fat(higher the
IV, higher the degree of unsaturation)
Iodine is used to halogenate double bond

4. Principle :-
1] fatty acids reacted with halogen (iodine) resulting in the
addition of the halogen at the
C=C double bond sites.
CH2 ₌ CH 2† ICl CHI−CHCl
2] the excess of iodine monochloride is treated with
potassium iodide.
ICl † KI KCl † I2
3] the liberated iodine estimated by titration with sodium
thiosulfate solution .
I2 † 2Na2S2O3 Na2S2O6 † 2NaI

5. Calculations:-
Iodine value = 12.69(B-S)N ⁄ W
Where, B = volume in ml of standard sodium thiosulphate
solution required for the blank .
S = volume in ml of standard sodium thiosulphate
solution required for the sample.
N = normality of the standard sodium thiosulphate
solution
W = wt in g of sample

6. Methods to determine the iodine value of fats and oils:-
1] Hubl’s method : carbon tetrachloride solution
of substance is treated with solution of iodine and
mercuric chloride in ethanol.
2] Wiji’s solution: iodine monochloride in glacial
acetic acid is used.
3] Dam’s solution: solution of glacial acetic acid is
use containing pyridine ,bromines and conc. Sulphuric acid.

7. Limitations :-
It does not take into account the number and
configuration of double bonds per molecule( only
the total number of double bond is recorded)

8. Oil/fat Iodine number
Milk fat
Olive oil
Coconut oil
Palm oil
Cocoa butter
Rice bran oil
Grape seed oil
Beef fat
Lard
Peanut
30-35
80-88
8-11
44-51
35-40
99-108
124-143
Approx.50
Approx.60
84-105

9. PEROXIDE VALUE
The peroxide value is figure used for determining
the peroxide oxygen .It is expressed in mill
equivalent of active oxygen per 1kg of fat.
Methods to determine the PV:-
•Fourier transform infrared spectroscopy(FTIR)
•Iodometric titration
•Ferric ion complexes

10. Principle :-
Peroxide value is a measure of the peroxides
contained in the oil. the peroxides present are
determined by titration against thiosulphate in the
presence of KI starch is used as an indicator.
Calculation:-
PV(milli equivalent peroxide /kg sample) = S × N × 1000 ⁄ g
sample.
where, S = ml sodium thiosulphate(test-blank)
N = normality of sodium thiosulphate

11. Factors that affect the rate of oxidation are the
following :-
 amount of oxygen present
degree of unsaturation of the lipids
 presence of antioxidants
presence of prooxidants ,especially copper and
some organic compounds such as heme-containing
molecules and lipooxidase
nature of packaging material
light exposure
temp. of storage

12. Steps of determining the peroxide value
•Weigh the sample accurately
•Dissolution of lipids in chloroform
•Acidification with acetic acid
•Addition of KI
•Incubate for 5 min
•Titration with sodium thiosulphate
ROOH † 2H+ † 2KI † I2 † ROH † H2 O † 2K+
I2 † 2Na2S2O3 Na2S2O6 † 2NaI

15. Oil/fat PV(meq/kg)
Olive oil
Sunflower oil
Cocoa butter
Maize oil
Rapeseed oil
7.99
7.10
3.32
4.21
3.82

16. RESEARCH
Blending of oil on storage stability and sensory characteristics of a ready to eat extruded snack
By – Dr. Sridevi Gutta and Dr. Kavita Waghray
Taking the nutritional evaluation of six different oil blends was
conducted using sesame oil as control. The oil blends selected were rice
bran, cottonseed, palmolein, mustard, and corn in the ratios of 80:20
and 20:80 with sesame. These oil blends were used by making a ready
to eat (RTE) extruded snack and store it 2months to examined the
changes in chemical and sensory characteristics.
RESULT- Near significant changes were observed in the oil extracted
from the fried product in comparison to control. Sensory evaluation of
the ready to eat(RTE) extruded snack indicated that it was chemically
acceptable up to two months of storage.

18. References :-
Deman
Florin
Thomas Alfred, 2002
Springer
Lipid Oxidation : Measurement
Methods
Analysis of Foods