This document discusses the properties and composition of fats and oils. It notes that fats and oils are triglycerides composed of glycerol and fatty acids. The fatty acid components can be differentiated by chain length, number and position of double bonds, and position on the glycerol. Short chain fatty acids have 4-10 carbons and are liquid at room temperature, while long chain saturated fatty acids have 14 or more carbons. Essential fatty acids like linoleic and linolenic acid cannot be synthesized by the human body. The document also discusses the physical properties of fats and oils such as crystallization, melting point, viscosity, and solubility and how they impact the behavior and characteristics of these

1. 1

2.  Chemically all the fats and oils are triglycerides or esters of glycerol and fatty
acids
 Three aspects can differentiate the fatty acid components;
 Chain length
 Number and position of double bonds
 Position of fatty acids regarding the glycerol
Short chain fatty acids
 Saturated fatty acids with only 4 to 10 carbon atoms are short chain fatty acids
 They naturally occur in milk fats, coconut and palm oil.
2

3.  All short chain fatty acids are liquid at room temperature
 Butyric acids has the least number of carbon atom (4-C) among all fatty acids
found naturally
 Cows milk contain 4% of butyric fatty acid which impart flavor to the butter
 Short chain fatty acids also impart the rancid flavor of butter when liberated
from the triglyceride by hydrolysis
 Short chain Fatty acids consists of lauric, myristic, palmitic, stearic fatty acids
3

4. Long chain saturated fatty acids
 Saturated fatty acids with carbon chain longer i.e. 14 more carbon atoms
 These fatty acids are found in most of the fats and oils including soya bean oil,
olive oil, fish, nuts etc.
 Long chain saturated fatty acids include oleic, arachidonic, behenic and
lignoceric fatty acids
 Oleic acid is the most widely distributed natural fatty acid
4

5.  High oleic oils normally have positive health aspects because of their;
• Low saturated fatty acid level
• Minimal trans isomer level
• Potential to reduce LDL cholesterol level
• High oxidative stability
 Olive oil is very flavor stable oil because of high oleic fatty acid content which
is 80%
 Peanut oil, lard, tallow and palm oil also have high oleic fatty acid content
typically 46.7, 43.9 and 42.5% respectively
5

6.  Liquid oils with high oleic acid contents normally have good flavor and
stability
 Oils with more than 65% oleic fatty acid lose some of the characteristics of
fried foods flavor
Essential fatty acids
 An essential nutrient is one that the human body cannot synthesized and must
obtained from diet
 Humans are unable to create fatty acid with double bonds beyond the 9th
carbon from the carboxyl end
 Linoleic acid and linolenic acid are classified as essential fatty acid
6

7.  These fatty acids also known as omega 6 (linoleic acid) and omega 3 (linolenic
acid)
Linoleic fatty acid/omega 6 (C-18:2)
 Linoleic fatty acid contain two double bonds at 9th carbon and 12th carbon
 Sunflower oil 68%, safflower oil 78%, corn oil 60%, cottonseed oil 54%,
soybean oil 54% linoleic acid
 It is quite flavor stable due to its relatively high tocopherol contents
 It also reverts to a flavor that is not as un pleasant as compared to other
vegetable oil
7

8. Linolenic acid/omega 3 (C-18:3)
 Linolenic fatty acid have double bonds at 9th , 12th and 16th carbon atoms
 Food in which off odors are detected first, are generally those that contain
significant amount of linolenic fatty acid
 Both canola and soybean oils contain high linolenic contents typically 8.8 and
7.6% respectively
 Oils with high linolenic acid contents are good drying oils for industrial uses
but relatively poor food oils due to rapid oxidation properties
 Rapeseed oil contains high erucic fatty acid content typically 41%
8

9. 9

10.  Physical properties of oils and fats allows us to understand the behavior and
characteristics of fats and oils, as well as their differences.
 Physical characteristics includes crystallization, the melting point, the
viscosity, the refractive index, the density, the solubility, the plasticity and the
emulsifying capacity
1. Crystallization
 Fats differ from oils in their degree of solidification at room temperature, since
in these conditions the oils are in a liquid state (not crystallized) while the fats
are in the solid (crystallized) state.
10

11.  The proportion of crystals in fats have great importance in determining the
physical properties of a product.
 Fats are considered solid when they have at least 10% of their crystallized
components.
 The fat crystals have a size between 0.1 and 0.5 μm and can occasionally reach
up to 100 μm.
 The crystals are maintained by Van der Waals forces forming a three-
dimensional network that provides rigidity to the product.
 An important feature of fat is its crystalline polymorphism since mono-di and
triglyceride crystallize in different crystalline forms (α, β, β’)
11

12.  Form α (vitreous state):
 Appears when the fat solidifies by a quick method.
 The crystals formed are of the hexagonal type and are organized randomly in
space.
 Form β:
 It occurs when the cooling is slow or if the tempering is carried out at a
temperature slightly below the melting point, this form being the most stable
of all.
 In the β form, tricyclic crystals are formed oriented in the same direction.
 The β form is typical of palm oil, peanut, corn, coconut, sunflower, olive and
lard.
12

13.  Form β’:
 It is produced from the tempering above the melting point of the α form.
 In the β-form, orthorhombic crystals are formed which are oriented in opposite
directions.
 The β’form is typical of modified partial cottonseed oil, fats, fats and modified
lard.
2. Melting point
 The melting point of a fat corresponds to the melting point of the β form which is
the most stable polymorphic form and is the temperature at which all the solids
melt.
13

14.  When short chain or unsaturated acids are present, the melting point is reduced.
 The melting point is of great importance in the processing of animal fats.
 The melting points of pure fats are very precise, but since fats or oils are made
up of a mixture of lipids with different melting points we have to refer to the
melting zone which is defined as the melting point of the fat component
3. Viscosity
 The viscosity of a fat is due to the internal friction between the lipids that
constitute it. It is generally high due to the high number of molecules that make
up a fat.
14

15.  By increasing the degree of unsaturation the viscosity decreases and when the
length of the chain increases the fatty acids components also increases the
viscosity.
4. Refractive index
 The refractive index of a substance is defined as the ratio between the speed of
light in air and in matter (oil or fat) that is analyzed.
 Increasing the degree of unsaturation increases the refractive index and when
the length of the chain increases, the refractive index also increases and that is
why it is used to control the hydrogenation process.
 As the temperature increases, the refractive index decreases.
15

16.  The refractive index is characteristic of each oil and fat, which helps us to
perform a quality control on them.
5. Density
 This physical property is of great importance when it comes to designing
equipment to process grease.
 Density decreases when fats dilate when going from solid to liquid
 When the fats melt, their volume increases and therefore the density decreases.
 For the control of percentages of solid and liquid in commercial fat,
dilatometric curves are used.
16

17. 6. Solubility
 Solubility has great relevance in the processing of fats.
 Fats are fully soluble in apolar solvents (benzene, hexane …).
 Except for phospholipids, they are completely insoluble in polar solvents
(water, acetonitrile). They are partially soluble in solvents of intermediate
polarity (alcohol, acetone)
 The solubility of fats in organic solvents decreases with increasing chain length
and degree of saturation.
 Phospholipids can interact with water because the phosphoric acid and the
alcohols that compose them have hydrophilic groups.
17

18.  Generally the surface tension increases with the length of the chain and
decreases with temperature.
 Surface tension and interfacial tension decrease with ease with the use of
surfactant agents such as monoglycerides and phospholipids.
7. Plasticity
 It is the property that has a body to preserve its shape by resisting a certain
pressure.
 The plasticity of a fat is caused by the presence of a three-dimensional network
of crystals inside which liquid fat is immobilized.
18

19.  For a grease to be plastic and extensible there must be a ratio between the solid
and liquid part (20 -40% solid state fat), the nets must not be tight and their
crystals must be in α form.
 The plastic fats act as a solid until the deforming forces that are applied break
the crystal lattice and the grease passes to behave like a viscous liquid and
therefore can be smeared.
8. Emulsifying capacity
 The emulsifying capacity is the capacity in the water / oil interface allowing
the formation of emulsion.
19

20. 9. Smoke point is the temperature at which a fat or oil produces a continuous
wisp of smoke when heated.
 This provides a useful characterization of its suitability for frying.
 The Canadian Government specifications define that frying oil should have a
smoke point above 200˚C.
10. Flash point defines the temperature at which the decomposition products
formed from frying oils can be ignited.
 This temperature ranges from 275˚C to 330˚C for different oils and fats
20

21.  Edible oils and fats are composed primarily of triglycerides, which are the ester
of one molecule of glycerol and three molecules of fatty acids.
 The fatty oils are mixtures of materials composed of hydrogen, oxygen, and
carbon.
 They are essentially Fatty Oils glycerides of the fatty acids.
 The predominating acid in the oils (or liquid fats) is the unsaturated oleic acid
 Proportion of the saturated acids, stearic and palmitic, increases as the solidity
of the oil or fat increases.
 The oils are saponifiable by alkalis to form soaps and glycerin
21

22.  Certain fatty oils will absorb oxygen from the atmosphere and tend to dry.
 Three classifications are designated on this basis as “drying,” semidrying,” and
“nondrying” oils, though members of the latter class will absorb small amounts
of oxygen.
 This so-called drying process results in the formation of a varnish-like film
which in time will become very hard.
 Linseed oil is an outstanding example of a drying oil, while lard oil is a good
example of a nondrying oil.
22

23. 1-Hydrolysis:
 They are hydrolyzed into their constituents (fatty acids and glycerol) by the
action of super heated steam, acid, alkali or enzyme (e.g., lipase of pancreas).
 During their enzymatic and acid hydrolysis glycerol and free fatty acids are
produced.
CH2 O
C H
O
CH2
C
C
O C
R1
R3
R2
O
O
O
3 H2O
H2C OH
C H
HO
H2C OH
OH
C
R1
O
OH
C
R3
O
+ OH
C
R2
O
Lipase or Acid
Triacylglycerol Glycerol Free fatty acids 23

24. 2-Saponification
 Alkaline hydrolysis produces glycerol and salts of fatty acids (soaps).
 Soaps cause emulsification of oily material this help easy washing of the fatty
materials
CH2 O
C H
O
CH2
C
C
O C
R1
R3
R2
O
O
O
H2C OH
C H
HO
H2C OH
ONa
C
R1
O
ONa
C
R3
O
+ ONa
C
R2
O
Triacylglycerol Glycerol Sodium salts of
fatty acids (soap)
3 NaOH
24

25. 3-Halogenation
 Neutral fats containing unsaturated fatty acids have the ability of adding
halogens (e.g., hydrogen or hydrogenation and iodine or iodination) at the
double bonds.
 It is a very important property to determine the degree of unsaturation of the fat
or oil that determines its biological value
CH (CH2)7 COOH
CH
CH2
CH
Linoleic acid
CH
(CH2)4
CH3
2 I2
CH (CH2)7 COOH
CH
CH2
CH
Stearate-tetra-iodinate
CH
(CH2)4
CH3
I
I I I
25

26. 4-Hydrogenation or hardening of oils
 It is a type of addition reactions accepting hydrogen at the double bonds of
unsaturated fatty acids.
 The hydrogenation is done under high pressure of hydrogen and is catalyzed
by finely divided nickel or copper and heat.
 It is the base of hardening of oils (margarine manufacturing), e.g., change of
oleic acid of fats (liquid) into stearic acid (solid).
 It is advisable not to saturate all double bonds; otherwise margarine produced
will be very hard, of very low biological value and difficult to digest.
Oils
(liquid)
(with unsaturated
fatty acids, e.g., oleic)
Hard fat
(margarine, solid)
(with saturated
fatty acids, e.g., stearic)
Hydrogen, high pressure, nickel
26

27. Advantages for hydrogenated oil or fat are as follows:
1. It is more pleasant as cooking fat.
2. It is digestible and utilizable as normal animal fats and oils.
3. It is less liable to cause gastric or intestinal irritation.
4. It is easily stored and transported and less liable to rancidity.
Disadvantages of hydrogenated
 Fats include lack of fat-soluble vitamins (A, D, E and K) and essential fatty
acids
27

28. 5-Oxidation(Rancidty)
 This toxic reaction of triglycerides leads to unpleasant odour or taste of oils and fats
developing after oxidation by oxygen of air, bacteria, or moisture.
 Also this is the base of the drying oils after exposure to atmospheric oxygen.
Example is linseed oil, which is used in paints and varnishes manufacturing
Rancidity
 It is a physico-chemical change in the natural properties of the fat leading to the
development of unpleasant odor or taste or abnormal color particularly on aging after
exposure to atmospheric oxygen, light, moisture, bacterial or fungal contamination
and/or heat.
 Saturated fats resist rancidity more than unsaturated fats that have unsaturated double
bonds.
28

29. Types and causes of Rancidity:
1. Hydrolytic rancidity
2. Oxidative rancidity
3. Ketonic rancidity
1-Hydrolytic rancidity:
 It results from slight hydrolysis of the fat by lipase from bacterial
contamination leading to the liberation of free fatty acids and glycerol at
high temperature and moisture.
 Volatile short-chain fatty acids have unpleasant odor.
29

30. 2-Oxidative Rancidity:
 It is oxidation of fat or oil catalyzed by exposure to oxygen, light and/or heat
producing peroxide derivatives which on decomposition give substances, e.g.,
peroxides, aldehydes, ketones and dicarboxylic acids that are toxic and have bad odor.
 This occurs due to oxidative addition of oxygen at the unsaturated double bond of
unsaturated fatty acid of oils.
3-Ketonic Rancidity:
 It is due to the contamination with certain fungi such as Asperigillus Niger on fats
such as coconut oil.
 Ketones, fatty aldehydes, short chain fatty acids and fatty alcohols are formed.
 Moisture accelerates ketonic rancidity.
30

31.  Fat constants or numbers are tests used for:
1. Checking the purity of fat for detection of adulteration.
2. To quantitatively estimate certain properties of fat.
3. To identify the biological value and natural characteristics of fat.
4. Detection of fat rancidity and presence of toxic hydroxy fatty acids.
31

32. 1-Iodine number (or value):
 Definition: It is the number of grams of iodine absorbed by 100 grams of fat or
oil.
 Uses: It is a measure for the degree of unsaturation of the fat, as a natural
property for it.
 Unsaturated fatty acids absorb iodine at their double bonds, therefore, as the
degree of unsaturation increases iodine number and hence biological value of
the fat increase.
 It is used for identification of the type of fat, detection of adulteration and
determining the biological value of fat.
32

33. 2-Saponification number (or value):
 Definition: It is the number of milligrams of KOH or NaOH required to
completely saponify one gram of fat.
 Uses:
 Since each carboxyl group of a fatty acid reacts with one mole of KOH during
saponification, therefore, the amount of alkali needed to saponify certain
weight of fat depends upon the number of fatty acids present per weight.
 Thus, fats containing short-chain acids will have more carboxyl groups per
gram than long chain fatty acids and consume more alkali, i.e., will have
higher saponification number.
33

34. 3-Acids Number (or value):
 Definition:
 It is the number of milligrams of KOH required to neutralize the free fatty
acids present in one gram of fat.
 Uses:
 It is used for detection of hydrolytic rancidity because it measures the amount
of free fatty acids present.
34

35. 4-Reichert- Meissl Number (or value):
 Definition: It is the number of milliliters of 0.1 N KOH required to neutralize
the water-soluble fatty acids distilled from 5 grams of fat. Short-chain fatty
acid (less than 10 carbons) is distillated by steam.
 Uses: This studies the natural composition of the fat and is used for detection
of fat adulteration.
 Butter that has high percentage of short-chain fatty acids has highest
Reichert-Meissl number compared to margarine.
35

36. 5-Acetyl Number (or value):
 Definition: It is number of milligrams of KOH needed to neutralize the acetic
acid liberated from hydrolysis of 1 gram of acetylated fat (hydroxy fat reacted
with acetic anhydride).
 Uses: The natural or rancid fat that contains fatty acids with free hydroxyl
groups are converted into acetylated fat by reaction with acetic anhydride.
 Thus, acetyl number is a measure of number of hydroxyl groups present.
 It is used for studying the natural properties of the fat and to detect
adulteration and rancidity.
36