Lipids
Components of Lipids Fatty Acids
Fats, and Oils
Chemical Properties of Triglycerides
1
Compiled by: Dwika Riandari, M.Si
Introduction
• Definition: water insoluble compounds
• Most lipids are fatty acids or ester of fatty acid • They are soluble in non-polar solvents such as
petroleum ether, benzene, chloroform • Functions
• Energy storage
• Structure of cell membranes
• Thermal blanket and cushion
• Precursors of hormones (steroids and
Components of Lipids
Waxes
Phospholipids Fatty Acids
Fats and oils (trigycerides) Fat soluble vitamins
Terpene Sterol
Waxes
Fatty acid + Long chain alcohol
Important in fruits:
1. Natural protective layer in fruits, vegetables, etc.
2. Added in some cases for appearance and protection.
Beeswax (myricyl palmitate), Spermaceti (cetyl palmitate)
O
C30H61 O C C15H31
O
5
Bee’s wax Spermaceti source
“TRIACONTANOILPALMITA T”
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Phospholipid
Lecithin (phosphatidyl choline)
O
O
H2C O C R O
R C O CH
H2C O P O CH2 CH2 N+ CH3 CH3 CH3
O_
Phosphatidic Acid Choline
Two hydroxyls of the glycerol residue are esterfied with fatty acids
The phosphoric acid end of the molecule is strongly polar hydrophylic
The fatty acid “tails” are non-polar
This dual structure (amphiphathic) makes the phospholipid valuable surface active agents and emulsion stabilizers
9
Sterols
Male & female sex hormones Bile acids
Vitamin D
Adrenal corticosteroids Cholesterol
HO
H3C
H3C
H3C CH3
CH3
1 2
3 4
5 6 7 8 9 10
111213
STEROID NUMBERING
SYSTEM
A B
C D
1 2
3
4 5 6
7 8
9 10
11
12
13
14 15
16 17
18
11
Fat Soluble Vitamins
Vitamin A
CH2OH
CH3 CH3
CH3 CH3 H3C
1 2
3 4 5
6 7 8
Vitamin D2
Vitamin E
HO
CH2 H
H H3C
H3C CH3 CH3
CH3
O R1
R2 HO
R
CH3
Fatty Acids
• Long-chain carboxylic acids • Insoluble in water
• Typically 12-18 carbon atoms (even
number)
• Some contain double bonds
corn oil contains 86%
unsaturated fatty acids and 14% saturated fatty acids
Saturated and Unsaturated
Fatty Acids
Saturated = C–C bonds
Unsaturated = one or more C=C bonds
Palmitic acid, a saturated acid
Palmitoleic acid, a unsaturated fatty acid COOH
Structures
Saturated fatty acids
• Fit closely in regular pattern
Unsaturated fatty acids
• Cis double bonds
15
COOH COOH COOH
C C
H H
COOH
cis double bond
Properties of Saturated
Fatty Acids
• Contain only single C–C bonds • Closely packed
• Strong attractions between chains • High melting points
17
Saturated Fatty Acids
Butyric Butanoic CH3(CH2)2COOH butterfat
Caproic Hexanoic CH3(CH2)4COOH butterfat, coconut, palm nut oils
Caprylic Octanoic CH3(CH2)6COOH Coconut, palm, nut oils, butterfat
Capric Decanoic CH3(CH2)8COOH Coconut, palm, nut oils, butterfat
Lauric Dodecanoic CH3(CH2)10COOH Coconut, palm, nut oils, butterfat
Myristic Tetradecanoic CH3(CH2)12COOH Coconut, palm, nut oil, animal fats
Palmitic Hexadecanoic CH3(CH2)14COOH practically all animal, plant fats
Stearic Octadecanoic CH3(CH2)16COOH animal fat, plant fats
Arachidic Eicosanoic CH3(CH2)18COOH peanut oil Common
Name
Systematic Name
Properties of Unsaturated
Fatty Acids
• Contain one or more double C=C
bonds
• Nonlinear chains do not allow
molecules to pack closely
• Few interactions between chains • Low melting points
Unsaturated Fatty Acids
19 Common Name Systematic NameFormula Common source
A. Monoethenoic Acids
Oleic Cis 9-octadecenoic C17H33COOH plant and animal fats Elaidic Trans 9-Octadecenoic C17H33COOH animal fats
B. Diethenoic Acids
Linoleic 9,12-Octadecadienoic C17H31COOH peanut, linseed, and cottonseed oils
C. Triethenoid Acids
Linolenic 9,12,15-Octadecatrienoic C17H29COOH linseed and other seed oils
Eleostearic 9,11,13-Octadecatrienoic C17H29COOH peanut seed fats
D. Tetraethenoid Acids
Moroctic
4,8,12,15-Octadecatetraenoic C17H27COOH fish oils Arachidonic
5,8,11,14-Eicosatetraenoic
C4 - 8
-C6 - 4 970
C8 16 75
C10 31 6
C12 44 0.55
C14 54 0.18
C16 63 0.08
Fatty Acids M.P.(C) mg/100 ml in H2O*
C18 70 0.04
Effects of Double Bonds on the Melting Points
Fatty Acids Melting point (C)
16:0 60
16:1 1
18:0 63
18:1 16
18:2 -5
18:3 -11
20:0 75
20:4 -50
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M.P.
# Double bonds
x
x
Important Fatty Acids for
Nutrition
• EPA (Eicosapentaenoic acid)
20:5(n-3). Omega-3, all-cis –eicosa-5,8,11,14,17 pentaenoic acid
• DHA (Docosahexaenoic acid)
Typical fish oil supplements
Fats and Oils
Formed from glycerol and fatty acids
+
HO C (CH2)14CH3 O
HO C (CH2)14CH3 O
HO C (CH2)14CH3 O
glycerol palmitic acid (a fatty acid) CH
Triglycerides
(triacylglycerols)
Esters of glycerol and fatty acids
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CH
CH2
CH2 O
O
O
C (CH2)14CH3 O
C (CH2)14CH3 O
C (CH2)14CH3 O
ester bonds
+
+
+
H2O
H2O
Properties of fats and oils
• fats are solids or semi solids • oils are liquids
• melting points and boiling points are not
usually sharp (most fats/oils are mixtures)
• when shaken with water, oils tend to
emulsify
• pure fats and oils are colorless and
odorless (color and odor is always a result of contaminants) – i.e. butter (bacteria
Examples of oils
• Olive oil – from Oleo europa (olive tree) • Corn oil – from Zea mays
• Peanut oil – from Arachis hypogaea • Cottonseed oil – from Gossypium
• Sesame oil – from Sesamum indicum • Linseed oil – from Linum usitatissimum • Sunflower seed oil – from Helianthus
annuus
• Rapeseed oil – from Brassica rapa • Coconut oil – from Cocos nucifera
Non-drying, semi-drying and
drying oils
• based on the ease of autoxidation and
polymerization of oils (important in paints and varnishes)
• the more unsaturation in the oil, the more likely the “drying” process
– Non-drying oils:
• Castor, olive, peanut, rapeseed oils
– Semi-drying oils
• Corn, sesame, cottonseed oils
– Drying oils
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Fatty Acids (%) of Fats and Oils
4 3
6 3
8 2 6
10 3 6
12 3 44
14 10 18 1
16 26 11 4 12
16:1 7 1
18:0 15 6 3 2
18:1 29 7 18 24
18:2 2 2 53 54
Fatty Acids Butter Coconut Cottonseed Soybean
Properties of Triglycerides
Hydrogenation
• Unsaturated compounds react with H2
• Ni or Pt catalyst
• C=C bonds C–C bonds
Hydrolysis
• Split by water and acid or enzyme
catalyst
Hydrogenation
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CH
CH2
CH2 O
O
O
C O
(CH2)5CH CH(CH2)7CH3
C O
(CH2)5CH CH(CH2)7CH3
C O
+
(CH2)5CH CH(CH2)7CH3
H2
Product of Hydrogenation
Hydrogenation converts double bonds in oils to single bonds. The solid products are used to make margarine and other
hydrogenated items.
CH
CH2
CH2 O
O
O
C (CH2)14CH3 O
C (CH2)14CH3 O
Hydrolysis
Triglycerides split into glycerol and three fatty acids (H+ or enzyme
catalyst) 33 CH CH2
CH2 O
O
O
C (CH2)14CH3 O
C (CH2)14CH3 O
C (CH2)14CH3 O
H2O +3
3
+ HO C (CH2)14CH3
O CH
CH2 OH
OH
CH2 OH
Saponification and Soap
• Hydrolysis with a strong base
• Triglycerides split into glycerol and
the salts of fatty acids
Soaps
• Process of formation is known as
saponification
– Types of soaps:
• Sodium soap – ordinary hard soap
• Potassium soap – soft soap (shaving soaps are
potassium soaps of coconut and palm oils)
• Castile soap – sodium soap of olive oil
• Green soap – mixture of sodium and potassium
linseed oil
• Transparent soap – contains sucrose • Floating soap – contains air
• Calcium and magnesium soaps are very poorly water
soluble (hard water contains calcium and magnesium salts –these insolubilize soaps)
Saponification
+ 3Na
+ -O C (CH
2)16CH3
O
CH
CH2 OH
OH
CH2 OH
CH CH2
CH2 O
O
O
C (CH2)16CH3 O
C O
(CH2)16CH3
(CH2)16CH3 C
O
+ 3 NaOH
salts of fatty acids (soaps)
Learning Check L1
How would the melting point of stearic acid compare to the
melting points of oleic acid and linoleic acid? Assign the melting points of –17°C, 13°C, and 69°C to the correct fatty acid. Explain.
stearic acid (18 C) oleic acid (18 C) linoleic acid (18 C)
Solution L1
Stearic acid is saturated and would
have a higher melting point than
the unsaturated fatty acids.
Because linoleic has two double
bonds, it would have a lower mp
than oleic acid, which has one
double bond.
Learning Check L2
What are the fatty acids in the following triglyceride?
39
CH
CH2
CH2 O
O
O
C (CH2)16CH3
O
C O
(CH2)7CH CH(CH2)7CH3
C O
(CH2)12CH3
Solutions L2
What are the fatty acids in the following triglyceride? Stearic acid Oleic acid Myristic acid CH CH2
CH2 O
O
O
C (CH2)16CH3
O
C O
(CH2)7CH CH(CH2)7CH3
C O
(CH2)12CH3
Learning Check L3
What are the products obtained from the complete hydrogenation of
glyceryl trioleate?
(1) Glycerol and 3 oleic acids (2) Glyceryltristearate
(3) Glycerol and 3 stearic acids
Solution L3
What are the products obtained from the complete hydrogenation of
glyceryl trioleate?
Analytical Methods for The
Determination of
Characteristics of Fats and
Oils
1. Acid Value
2. Saponification Value
3. Iodine Value
4. Gas Chromatographic Analysis for Fatty Acids
5. Liquid Chromatography
6. Cholesterol Determination
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Acid Value
Number of mgs of KOH required to neutralize the Free Fatty Acids in 1 g of fat.
AV = ml of KOH x N x 56
Weight of Sample = mg of KOH RCOOH + KOH RCOO- K+ + H
Acid Value
The free fatty acid content in a good soybean oil should be less than or equal to 0.05 %. The average molecular
weight of free fatty acids of the oil is 280 which is the molecular weight of linoleic acid.
What is the maximum acid value of the good soybean oil?
•
The free fatty acid content in soybean
oil is 0.05%.
•
What is the content of free fatty acid in
1g oil in mg?
•
1g = 1000mg
•
What is the 1% of 1000mg in mg?
•
What is the 0.1% of 1000 mg soybean
oil in mg?
•
What are the 0.5% of 1000mg soybean
Acid Value
0.05 % in
1 gram
is 0.5 mg RCOOH in
1 gram of oil
56 mg of KOH reacts with 280 mg of RCOOH
56 mg of KOH / 280 mg of RCOOH = 1 : 5
The 0.5 mg RCOOH reacts with 0.1 mg KOH
• What is the content (%) of free fatty acids
of soybean oil if the acid value is 0.3?
• Acid value 0.3 means that 0.3 mg KOH is
required to react with the free fatty acid in1g (1000mg) of oil
• The 56mg KOH reacts with 280 mg free
fatty acid, 56 : 280 =1 : 5
• 1mg KOH reacts with 5 mg free fatty acid • The 0.3 mg KOH reacts with 1.5 mg of
free fatty acid in 1 gram oil
• 1.5 mg free fatty acid /1000 mg oil
x100(%) =0.15 %
Saponification Value
Saponification - Hydrolysis of ester (triglyceride) under alkaline condition.
O
C R O O
C R
C R O H2C O
HC O H2C O
KOH
H H H
H2C O HC O H2C O
R C O-K+
+ 3 Heat + 3
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Saponification # --mgs of KOH required to saponify 1 g of fat. 1. 5 g in 250 ml Erlenmeyer.
2. 50 ml KOH in Erlenmeyer. 3. Boil for saponification.
4. Titrate with HCl using phenolphthalein. 5. Conduct blank determination.
Saponification number =[ (B – S) x N of HCl x 56] /gram of sample
B - ml of HCl required to titrate KOH in Blank.
S - ml of HCl required to titrate excess KOH by Sample.
Saponification Value
CH2 O CO (CH2)6 CH3
CH O C O
(CH2)6 CH3
CH2 O C O
(CH2)6 CH3
CH2 O C O
(CH2)16 CH3 CH O C
O
(CH2)16 CH3 CH2 O C
O
(CH2)16 CH3
Tricaprylin (MW= 450)
Tristearin (MW= 890)
1Gram of Oils A and B
A
Saponification Value
1 mol TG 3 mol KOH required
MWKOH = 56 g/mol, therefore weight of 1 mol KOH =
56000 mg
1 g TG => 1 g / MWTG (g/mol) mol
1 mol TG 3x 56000 mg KOH required
1 g TG / MWTG X mg KOH required
53
TG
MW
168000
SN
Saponification Value
• What is the MWTG ?
TG
MW
168000
SV
X
O C C O C O O O O R R R HC
H2C
H C O C C O C O O O O R1 R1 R2 HC
H2C
H2C
O C C O C O O O O R1 R2 R3 HC
H2C
Saponification Value
• Which one’s MW
should be taken?
TG
MW
168000
SV
X
55 O C C O C O O O O R R R HC
H2C
H2C
O C C O C O O O O R1 R1 R2 HC
H2C
H2C
O C C O C O O O O R1 R2 R3 HC
H2C
Saponification Value
• The Answer is the Weighted Average
MW
TG
AMW
168000
SV
X
O C C O C O O O O R R R HC
H2C
H C O C C O C O O O O R1 R1 R2 HC
H2C
H2C
O C C O C O O O O R1 R2 R3 HC
H2C
57
Sample A has large molecular weight triglyceride (e.g. MW.890).
Sample B has small molecular weight triglyceride(e.g. MW.450).
In one gram of sample, number of triglyceride in B is about two times
more than number of triglyceride in A.
Less mg of KOH is needed to saponify sample A than sample B.
Therefore, saponification value of A is about half of that of sample B
Learning Check
A 5.00 grams of exotic tropical oil was saponified with excess KOH. The unreacted KOH was then
titrated with 1.00 N HCl. The blank required 40 mL of HCl and the sample required 20 mL.
•Please calculate the saponification value of the oil.
•Please calculate the MWTG
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Milk Fat 210-233
Coconut Oil 250-264
Cotton Seed Oil 189-198
Soybean Oil 189-195
Fat Saponification #
Lard 190-202
Iodine Value
Number of iodine (g) absorbed by 100 g of oil.
Iodine Value
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Trilinolein (MW= 878) Triolein (MW= 884)
CH2 O C
O
(CH2)7 CH CH (CH2)7 CH3
CH3
(CH2)7
CH CH
(CH2)7
O C O CH
CH3
(CH2)7
CH CH
(CH2)7
O C O CH2
CH2 O C O
(CH2)7 CH CH CH2 CH
CH CH
(CH2)7 O C O CH CH CH
(CH2)7 O
C O CH2
CH (CH2)4 CH3 CH3 (CH2)4
CH CH
CH2
CH3 (CH2)4
CH CH
CH2
A
(ml of Na2S2O3 volume for blank - ml of Na2S2O3 volume for sample) N of Na2S2O3 0.127g/meq
100
ICl KI KCl
I2
I2
Na2S2O3 Na2S4O6 NaI
+
+ 2 + 2 +
Excess unreacted ICl
Iodine Value Determination
Iodine Value =
CH CH CH CH Cl I ICl
Iodine chloride
+
Determination of Double Bonds
per Molecule
63
Iodine Value x Molecule Weight
2 x 127 x 100 Number of Double
Double Bond Determination
The unknown compound has molecular weight of 878 and iodine value of 173. Determine the number of double bonds in the unknown
• Fatty acids A and B have only one double
bond per molecule. The molecular weights of A and B are 150 and 300, respectively. The hypothetical iodine value of Compound A is
150. What is the Iodine value of compound B?
• Triglycerides A and B have the very similar
molecular weights of about 878. The
compound A has 6 double bonds per molecule and has iodine value is 174. The compound B has 3 double bond per molecule. What is the iodine value of the compound B?
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