Lipids are a diverse group of compounds that are generally insoluble in water but soluble in organic solvents. They include fatty acids, triglycerides, phospholipids, sterols, and waxes. Triglycerides are the main form in which fatty acids are stored and transported in the body, providing energy and essential fatty acids. Phospholipids are an important component of cell membranes. Cholesterol is a key animal sterol while plants contain phytosterols. Essential oils contain terpenes that give plants distinctive aromas and flavors.
1. LIPIDS.
2. PROPERTIES OF LIPIDS.
3. FATTY ACIDS.
4. USES AND CLASSIFICATION OF FATTY ACIDS.
5. STRUCTURE AND CLASSIFICATION OF LIPIDS.
PHOSPHOLIPIDS: A class of lipid that is a key component of all cell membranes, as they can form lipid biomarkers. Composition: It is composed of phospholipids. i. Glycerol: one molecule ii. Fatty acids: Two molecules. iii. Phosphoric acid: one molecule. When a nitrogen-containing phospholipid group is attached to the end of the phospholipid, it is called phosphatidylcholine. Phospholipids consist of two parts i) Chapter: The head is polar in nature, soluble in water (hydrophilic). n) Tails: Nature has a non-polar tail, insoluble in water (hydrophobic).
Washes: Wax lipids are derived. Wax is a fatty acid ester and chronic alcohol: The wax is composed of i) a long-chain fatty acid ... one molecules ii) long-chain alcohol with one hydroxyl group (-OH), i.e. Cylinder wax is hydrophobic in nature. They have a high melting point, solid at room temperature. it gives stability and declines. On the surfaces of parts of plants, e.g. The leaves and fruits produce a waterproof layer, reducing the rate of perspiration. Wax is also a layer of wax that covers the bodies of animals, e.g., slime, insects, etc.
STEROIDS: Steroids fall under the lipid categories: Steroids are derived from lipid composition: proper arrangement of 3 cyclohexyl rings and 1 cyclopentane ring, a total of 17 carbon atoms in four carbon rings. Steroids do not contain alcohol and fatty acids.
Steroids Examples of steroids: i) Cholesterol: an important factor in animal cells. The precursor of all hormonal molecules such as aldosterone, sex hormone, and vitamin D ii) Aldosterone helps regulate Na+ions in the blood iii) Sex hormones e.g. testosterone, progesterone, and estrogens help to preserve the characteristics of males and females.
TERPENOIDES: It contains a very different class of organic compounds. Terpenoids are lipid derivatives, soluble in fat and soluble in water. Don't use molecule acids like fats. Composite units which they call isoprenoid or isoprenes. Isoprene unit: Hydrocarbon containing five carbon atoms with a branched-chain structure. Isoprene units bind to each other through the condensation process resulting in different types of compounds, e.g. Carotenoids, terpenes, and rubbers, etc.
CAROTENOIDS: Carotenoids are yellow, orange, red, or brown in plants. There are two kinds: i) Carotene: ii) Xanthophylla, i) Carotene: Orange is the genus of carotene, with red color, beta carotene. carrot & rice. Breakdown of beta-carotene leaves two molecules of vitamin A in the human body. n) Xanthophyllus: the auxiliary yellow color found in plants.
6 STORAGE LIPIDS.
7. USES OF LIPIDS.
# ALL ABOUT LIPIDS BY AUTHENTIC BOOKS.
A Comprehensive Introduction to Lipids and its chemistry, classification, qualitative tests and disorders related to its metabolism. This will give readers a overall insight to this topic. All types of queries and suggestions are most welcome
1. LIPIDS.
2. PROPERTIES OF LIPIDS.
3. FATTY ACIDS.
4. USES AND CLASSIFICATION OF FATTY ACIDS.
5. STRUCTURE AND CLASSIFICATION OF LIPIDS.
PHOSPHOLIPIDS: A class of lipid that is a key component of all cell membranes, as they can form lipid biomarkers. Composition: It is composed of phospholipids. i. Glycerol: one molecule ii. Fatty acids: Two molecules. iii. Phosphoric acid: one molecule. When a nitrogen-containing phospholipid group is attached to the end of the phospholipid, it is called phosphatidylcholine. Phospholipids consist of two parts i) Chapter: The head is polar in nature, soluble in water (hydrophilic). n) Tails: Nature has a non-polar tail, insoluble in water (hydrophobic).
Washes: Wax lipids are derived. Wax is a fatty acid ester and chronic alcohol: The wax is composed of i) a long-chain fatty acid ... one molecules ii) long-chain alcohol with one hydroxyl group (-OH), i.e. Cylinder wax is hydrophobic in nature. They have a high melting point, solid at room temperature. it gives stability and declines. On the surfaces of parts of plants, e.g. The leaves and fruits produce a waterproof layer, reducing the rate of perspiration. Wax is also a layer of wax that covers the bodies of animals, e.g., slime, insects, etc.
STEROIDS: Steroids fall under the lipid categories: Steroids are derived from lipid composition: proper arrangement of 3 cyclohexyl rings and 1 cyclopentane ring, a total of 17 carbon atoms in four carbon rings. Steroids do not contain alcohol and fatty acids.
Steroids Examples of steroids: i) Cholesterol: an important factor in animal cells. The precursor of all hormonal molecules such as aldosterone, sex hormone, and vitamin D ii) Aldosterone helps regulate Na+ions in the blood iii) Sex hormones e.g. testosterone, progesterone, and estrogens help to preserve the characteristics of males and females.
TERPENOIDES: It contains a very different class of organic compounds. Terpenoids are lipid derivatives, soluble in fat and soluble in water. Don't use molecule acids like fats. Composite units which they call isoprenoid or isoprenes. Isoprene unit: Hydrocarbon containing five carbon atoms with a branched-chain structure. Isoprene units bind to each other through the condensation process resulting in different types of compounds, e.g. Carotenoids, terpenes, and rubbers, etc.
CAROTENOIDS: Carotenoids are yellow, orange, red, or brown in plants. There are two kinds: i) Carotene: ii) Xanthophylla, i) Carotene: Orange is the genus of carotene, with red color, beta carotene. carrot & rice. Breakdown of beta-carotene leaves two molecules of vitamin A in the human body. n) Xanthophyllus: the auxiliary yellow color found in plants.
6 STORAGE LIPIDS.
7. USES OF LIPIDS.
# ALL ABOUT LIPIDS BY AUTHENTIC BOOKS.
A Comprehensive Introduction to Lipids and its chemistry, classification, qualitative tests and disorders related to its metabolism. This will give readers a overall insight to this topic. All types of queries and suggestions are most welcome
bio chemistry
كيمياء حيوية جامعة الملك سعود
chemistry
كيمياء جامعية
0503964728
محمد منير كيمياء
ابو يوسف
all branched of chemistry bio chemistry - organic chemistry - inorganic chemistry - analytically - spectra - d-block
“These are the naturally Organic compounds, insoluble in water, soluble in organic solvents (alcohol, ether, etc.), which are potentially related to fatty acids & utilized by living cells."
Lipids are a heterogeneous group of compounds.
They are esters of fatty acids. Lipids occur widely in plants and animals. Lipids include fats, oils, waxes, and related compounds.
Lipids are a family of organic compounds, composed of fats and oils. These molecules yield high energy and are responsible for different functions within the human body.
bio chemistry
كيمياء حيوية جامعة الملك سعود
chemistry
كيمياء جامعية
0503964728
محمد منير كيمياء
ابو يوسف
all branched of chemistry bio chemistry - organic chemistry - inorganic chemistry - analytically - spectra - d-block
“These are the naturally Organic compounds, insoluble in water, soluble in organic solvents (alcohol, ether, etc.), which are potentially related to fatty acids & utilized by living cells."
Lipids are a heterogeneous group of compounds.
They are esters of fatty acids. Lipids occur widely in plants and animals. Lipids include fats, oils, waxes, and related compounds.
Lipids are a family of organic compounds, composed of fats and oils. These molecules yield high energy and are responsible for different functions within the human body.
Lipid Chemistry-Complete - Alex -Dr Ayman- 2015 - 2016 - More Detailed.pptAyman Abdo
This presentation shows the classification and occurrence of human lipids and their biological value. It also reveals the chemical formula of human lipids
1. General Information
• Definition
– Substances found in living tissues which are
generally insoluble in water and are soluble in
organic solvents (e.g. ether, chloroform,
hexane)
– Exceptions
• Some lipids (such as short chain fatty acids - < 4
carbons long) are water soluble
• Others are only soluble in a limited range of
organic solvents
2. General Information
• Use of fats and oils in body
– Source of energy
• For all cells except erythrocytes and cells of central
nervous system (which use carbohydrates for the
most part)
– Carriers of fat-soluble vitamins (A, D, E, K)
– Carrier of food flavors
• Most dietary lipids are triglycerides which are
relatively tasteless on their own
3. General Information
– Help provide food texture that increases
palatability (i.e. improves mouthfeel)
– Delays gastric emptying (which contributes to
satiety)
– Adipose tissue insulates and cushions organs
– Supplies essential fatty acids
4. General Information
• Metabolic energy from lipids
– calorie = the quantity of heat required to raise
the temperature of 1.0 g of water by 1 degree
Celsius (°C)
– 1000 calories = 1 kilocalorie (abbreviated as
kcal) = 1 Calorie (abbreviated as Cal)
– In general, lipids are 9 kcal/g (or 9 C/g)
10. Nomenclature – fatty acids
• Nomenclature of fatty acids requires both a
systematic approach and a knowledge of
trivial names
11. Nomenclature – fatty acids
• Systematic
– Names of fatty acids are derived from the
appropriate parent hydrocarbon
– Remove terminal “e” from parent and add suffix
“oic”
– Example
• Hexane: CH3CH2CH2CH2CH2CH3
• Hexanoic acid: CH3(CH2)4COOH
12. Nomenclature – fatty acids
– 2 main classes of fatty acids
• Saturated: no double bonds
• Unsaturated: double bonds present in carbon chain
– If 1 double bond, the parent alkene becomes
“enoic acid”
• Example
– 3-hexene: CH3CH2CH=CHCH2CH3
– 3-hexenoic acid: CH3CH2CH=CHCH2COOH
– If 2 double bonds, use the suffix “dienoic”
• Similarly for:
– 3 double bonds, use “trienoic”
– 4 double bonds, use “tetraenoic”
– Etc.
13. Nomenclature – fatty acids
• Trivial names
– Names were selected prior to the identification of
the fatty acid’s chemical structure
– Name often identified the source of the fatty acid
– Examples:
• Saturated
– C12: Lauric
– C14: Myristic
– C16: Palmitic
– C18: Strearic
– C20: Arachidic
17. Nomenclature – fatty acids
• Most naturally occurring fatty acids have
unconjugated double bonds
– Double bonds are separated by one or more
single bonded C atoms
– In most cases, double bonds are methylene
interrupted Methylene group
• CH2-CH=CH-CH2-CH=CH-
• Conjugated double bonds
– Double bonds adjacent to one another
• CH2-CH=CH-CH=CH-
18. The Biochemical ω-system
• Animals cannot synthesize ω-3 or ω-6 fatty
acids themselves
– Animals lack the enzymes that catalyze
desaturation towards the methyl end
• Enzymes in the body cannot function that close to the
methyl end
• Can elongate and desaturate towards carboxyl end
– Plants and microorganisms can desaturate
towards the methyl end
Since animals cannot make 18:2ω-3 or 18:ω-6 ,
they are termed Essential Fatty Acids (EFA)
19. Nomenclature – fatty acids
• Using the omega notation can give necessary
information in a brief way
– Example: What do we know from 18:2ω6?
» 18 carbons
» 2 double bonds
» 1st double bond is 6 carbons down from the methyl end
» Since we know that most double bonds are methylene
interrupted, the 2nd double bond is 9 carbons down from
the methyl end
CH3(CH2)4CH=CH-CH2-CH=CH(CH2)7COOH
20. Nomenclature – fatty acids
• What is the omega nomenclature of this
fatty acid (please type into the chat
space).
21. Nomenclature – fatty acids
• What is the delta nomenclature of this fatty
acid (please type into the chat space).
Include all double bond locations.
22. Nomenclature – fatty acids
• What is the common (i.e. trivial) name of
this fatty acid (please type into the chat
space).
23. Nomenclature – fatty acids
• Cis versus trans
– Most unsaturated fatty acids in nature will exist in
the cis configuration
• If the fatty acid is in the trans configuration, it will be
stated
– The two configurations will yield different
properties at room temperature
Oleic Acid: 18:1ω9
Elaidic Acid: 18:1ω9t
Liquid at Troom
Solid at Troom
24. EFA’s and deficiency
• Linoleic (18:2ω-6) deficiency
– Clinical symptoms
• Scaly skin, water loss through skin, extreme thirst,
poor wound healing, failure to gain weight, impaired
reproduction, death
• Linolenic (18:3ω-3) deficiency
– Noticed symptoms
• Blurred vision, neurological symptoms, tingling
extremities
– Linolenic is critical to prostaglandin formation
25. Omega 3 fatty acids
– 18:3ω-3 found in:
• Soybean oil (~7%)
• Canola oil (~10%) VERY susceptible to
oxidative rancidity =
• Linseed oil (~50-60%) degradation
• Green leafy vegetables
• Desaturated 20:5ω-3 (EPA) in marine oils
– Studied Eskimos in Greenland: found a decrease
in coronary heart disease compared to
populations consuming less marine foods
26. Omega 3 fatty acids
• Desaturated 20:5ω-3 (EPA) in marine oils
– Studied Eskimos in Greenland: found a decrease
in coronary heart disease compared to
populations consuming less marine foods
27. Other fatty acids of interest
• Vaccenic acid
– 18:1Δ-11trans (18:1ω-7trans); also 18:1Δ11
– Trans fatty acids that occur in milk and butterfat
due to biohydrogenation in rumen
• Ricinoleic acid
– 12-OH octadeca cis-9-enoic acid
– Oleic acid with an OH group on carbon 12 from
COOH end
– Castor oil
• Laxative
28. Other fatty acids of interest
• Erucic acid
– 22:1ω-9 rapeseed and mustard oils
– Accumulates in heart tissue when fed to rats
– Genetic variant is canola oil, or low erucic acid
rapeseed (LEAR)
• Branched chain
– Iso: mainly even C’s
– Anteiso: mainly odd C’s
– Occur in waxes like wool wax
29. Other fatty acids of interest
• Milk fat group
– Fats derived from milk of domesticated land
animals
• Characteristic shorter chain fatty acids (C4 – C12) in
milk fat
– Influences milk flavor and how milk is processed into dairy
products
• C4: butyric acid
– A fatty acid that is liquid at Troom although saturated
– Normally masked in foods
– If broken down via lipolysis, it will be very pungent
» Occurs due to extreme heat or agitation
30. Other fatty acids of interest
• Lauric acid group
– C12 is present
– Coconut oil
• Vegetable butter group
– Cocoa butter
• Oleic-linoleic acid group
– MAJOR GROUP
– Vegetable oils
– Saturated acids >20%
31. Other fatty acids of interest
• Linolenic acid group
– Contains 18:3
– Soybean oil ~8% 18:3
• Animal fat group
– 30-40% saturated
– ~60% unsaturated
– Lard, tallow
• Marine fat group
– Highly unsaturated
32. Major Lipid Components –
Acylglycerols
• The majority of fatty acids are esterified to
glycerol, making them acylglycerols
• Triacylglycerols are the most common in
foods
– Mono- and diacylglycerols do exist as food
additives
33. Major Lipid Components –
Acylglycerols
• Review of ester formation
– Ester linkage forms between the carbon atom
of carboxylic acid on the fatty acid chain and
the oxygen atom of the alcohol on the glycerol
backbone
O O
R-C-OH + R’OH R-C-OR’ + H2O
O
R : Fatty acid chain C-OH : Carboxylic acid OH : Alcohol
34. Major Lipid Components –
Acylglycerols
– Observe ester linkage
Glycerol Triacylglycerol = Triglyceride
H H
O
H-C-OH
H-C-O-C-R1
H-C-OH + 3 fatty acids O + 3 H2O
H-C-OH H-C-O-C-R2
O
H
H-C-O-C-R3 1 mol of water
is given off for
every mol of “R”
H participating in
the reaction
35. General Lipid Categories
• Simple lipids (neutral lipids)
– Esters of fatty acids and alcohols; lipids
derived from these by alkaline and acid
hydrolysis (derived lipids)
– Includes fatty acids, glycerides, fatty alcohols
– Examples
• Triacylglycerols (i.e. triglycerides)
– Esters of fatty acids and glycerol
• Waxes
– Esters of fatty acids with alcohols other than glycerol
– Normally: long chain alcohols (e.g. C24)
– Water insoluble
36. General Lipid Categories
• Compound (complex) lipids
– Lipids containing other groups in addition to
an alcohol-fatty acid ester linkage
– Phospholipids
• Phosphoglycerides or glycerophospholipids
• Glycerol + fatty acids + phosphate + another group
• Example: phosphatidic acid (major component of
cell membranes)
37. General Lipid Categories
• Example: cardiolipin (a phosphatidyl glycerol)
– An important component of the inner mitochondrial
membrane
– Important to the electron transport chain that produces ATP
38. General Lipid Categories
• Example: Phosphatidyl-
Choline (component of lecithin) Ethanolamine (membrane lipid)
Serine (for NS cell functioning) Inositol (substrate for cell signaling
enzymes)
39. General Lipid Categories
– Sphingolipids
• Associated with plant and animal membrane
components
• Play an important role in both signal transmission
and cell recognition
• Sphingosine + derived lipids + water soluble
products
– No glycerol backbone
41. General Lipid Categories
– Sterols, other lipids and essential oils
• All contain the cyclopentanoperhydrophenanthrene
ring system
http://journals.iucr.org/a/issues/2006/02/00/xo5005/xo5005fig1.html
42. General Lipid Categories
– Sterols, other lipids and essential oils
• Cholesterol: typical in animals
– Plants do have detectable levels, but VERY low
– Has the ability to undergo oxidation, leading to heart
disease and cancer
» Low density lipoprotein oxidation can lead to plaque
43. General Lipid Categories
• Phytosterols: plant sterols
– Example: stigmasterol (in soybeans)
– May reduce the risk of CHD by lowering blood cholesterol
levels
44. General Lipid Categories
• Essential oils
– Not “oils” in the real sense
• Actually terpenes ((C5H8)n hydrocarbons)
– Often mixed with other lipids in waxy coats or
located in special oil sacs in the skin of citrus
fruits
– Important to citrus-based flavor development
45. Natural fat and oil composition
• Fats of aquatic origin
– Number of carbons usually exceeds 20
• Mainly C14 – C24
– Major saturated acid is palmitic (16:0): 15-20%
by wt.
– Monoenoic acids are 16:1, 18:1, and 20:1
• Usually with double bond position at 9, but some have
double bond at carbon 1
– Many C16, C18, C20, and C22 polyenoic acids
• ω3 family: 18:3, 18:4, 20:4, 20:5, 22:5, and 22:6
46. Natural fat and oil composition
– Other lipids present
• Glycerol ethers
• Waxes
– Occur occasionally as an oil of the sperm whale
– Ester of long chain alcohol and a fatty acid
47. Natural fat and oil composition
• Milk fats
– Cow’s milk fat
• High in C4 – C10 fatty acids: 20 – 30% on a molar
basis
– Human milk fat
• Much lower in C4 – C10, but higher in C12 – C14
48. Natural fat and oil composition
• Vegetable fats (usually oils)
– Present in all parts of plants but usually highest
in fleshy part of fruit or in seeds (seed oils)
– Oils and fats from different parts of plant differ in
composition
49. Natural fat and oil composition
• Example: Erucic acid (22:1Δ13) in rapeseed plant
– No erucic acid in leaves
– In rapeseed oil, there’s approximately 40 – 50% erucic acid
– Problem
» Erucic acid accumulates in heart muscle, not in adipose
tissue, upon feeding
» Heart lacks enzyme for oxidizing erucic acid
» Could be a problem if an excess of one fatty acid
accumulates in heart muscle membranes
» The problem was avoided with the development of low
erucic acid rapeseed oil (LEAR)
51. Natural fat and oil composition
• Depot fats of land animals
– Adipose tissue fat
• Fats are laid down in adipose tissue as triglycerides
• Two sources of fatty acids
– Endogenous supply from CHO and protein synthesis
– Dietary fat (this may be modified by the animal)
• Easy to distinguish from fish oils as they are solid or
semi-solid at Troom
52. Natural fat and oil composition
• Characteristics
– Almost entirely C16 (32%) and C18 (62%) fatty acids
– C16 is almost all 16:0
– C18 is almost all 18:1
– Stearic-rich (18:0) fats come from ruminants such as sheep,
cattle, and deer
» Hydrogenation of fatty acids by rumen bacteria
» Also due to hydrogenation in rumen, small amounts of
trans fatty acids
» The fatty acid composition of adipose tissue can be
changed drastically by changing animal’s diet – pig feed
high in 18:2 (corn) can result in “soft-pork” problem (i.e.
soft adipose tissue = runny fat)
53. Natural fat and oil composition
• Summary
– Animals do not generally produce linoleic and
linolenic acids (EFA), thus they must acquire it
from their diet
– Plants produce linoleic and linolenic, but carry
out less conversion to the longer, more
unsaturated fatty acids
– Microorganisms are versatile
• They can produce all kinds of fatty acids including
branched chain, hydroxyl, keto, and cyclic fatty acids
54. Lipid properties
Table 1. Physicochemical property comparison – Triolein oil vs. water
Property Oil Water
Molecular weight 885 18
Melting point (ºC) 5 0
Density (kg/m3) 910 998
Viscosity (mPa*s) ~50 1.002
Specific heat (J/kg*K) 1980 4182
Refractive index 1.46 1.33
55. Lipid properties
• Refractive index (RI)
– Used to determine what the fatty acid
composition might be
– A ratio of the velocity of light in air to the velocity
of light in the substance
– A function of the temperature and wavelength of
light employed
56. Lipid properties
– Extent of refraction depends on intermolecular
attractions
• Refraction
57. Lipid properties
– Bending of light as it passes from one medium to another
– The density of the medium impacts the speed of light through
the medium
» This causes the light to bend at different angles
– Extent of refraction is also impacted by intermolecular
attractions
– RI increases with increasing chain length and with increasing
unsaturation (i.e. number of double bonds)
– Use in industry
» As a control procedure during hydrogenation (a change
in RI results when the number of double bonds changes)
58. Lipid properties
• Iodine value
– The number of grams of iodine absorbed by 100
grams of fat
– Measure of the degree of UNsaturation
– Halogens (e.g. Cl, Br, I) react with double bonds
in fatty acids under mild conditions
59. Lipid properties
– The reaction results in addition to the double
bond
H H H H
I2
-C=C- -C - C-
I I
60. Lipid properties
Calculation of Iodine Value – Oleic Acid
CH3(CH2)7CH=CH(CH2)7COOH
1 mol of I2 adds across each double bond –
therefore, in the case of oleic acid, 1 mol of I2
will add across the 1 double bond in oleic
acid
61. Calculation of Iodine Value: Oleic Acid (18:1Δ-9)
CH3(CH2)7CH=CH(CH2)7COOH
For each mol of lipid, 1 mol of I2 will add across each double bond.
Therefore in the case of oleic acid, with one double bond, 1 mol of I2 will
add to 1 mol of oleic acid.
Since we know the molecular weights of both oleic acid (282g/mol) and I2
(254g/mol) we can establish a mass ratio on a per mol basis that we can
use to calculate how many grams of I2 will add across 100g of oleic acid.
In other words, if 1 mol of I2 adds to 1 mol of oleic acid, then 254g of I2 add
to 282 g of oleic acid. Thus, we can determine how many grams of I2
add to 100g of oleic using the following ratio:
62. Calculation of Iodine Value: Oleic Acid (18:1Δ-9)
CH3(CH2)7CH=CH(CH2)7COOH
For each mol of lipid, 1 mol of I2 will add across each double bond.
Therefore in the case of oleic acid, with one double bond, 1 mol of I2 will
add to 1 mol of oleic acid.
Since we know the molecular weights of both oleic acid (282g/mol) and I2
(254g/mol) we can establish a mass ratio on a per mol basis that we can
use to calculate how many grams of I2 will add across 100g of oleic acid.
In other words, if 1 mol of I2 adds to 1 mol of oleic acid, then 254g of I2 add
to 282 g of oleic acid. Thus, we can determine how many grams of I2
add to 100g of oleic using the following ratio:
254gI2 XgI2
=
282gOleic Acid 100gOleic Acid
63. Calculation of Iodine Value: Oleic Acid (18:1Δ-9)
CH3(CH2)7CH=CH(CH2)7COOH
For each mol of lipid, 1 mol of I2 will add across each double bond.
Therefore in the case of oleic acid, with one double bond, 1 mol of I2 will
add to 1 mol of oleic acid.
Since we know the molecular weights of both oleic acid (282g/mol) and I2
(254g/mol) we can establish a mass ratio on a per mol basis that we can
use to calculate how many grams of I2 will add across 100g of oleic acid.
In other words, if 1 mol of I2 adds to 1 mol of oleic acid, then 254g of I2 add
to 282 g of oleic acid. Thus, we can determine how many grams of I2
add to 100g of oleic using the following ratio:
254gI2 XgI2
=
282gOleic Acid 100gOleic Acid
(254gI2)(100gOleic Acid) = (XgI2)(282gOleic Acid)
X = 90gI2
64. Calculation of Iodine Value: Oleic Acid (18:1Δ-9)
CH3(CH2)7CH=CH(CH2)7COOH
For each mol of lipid, 1 mol of I2 will add across each double bond.
Therefore in the case of oleic acid, with one double bond, 1 mol of I2 will
add to 1 mol of oleic acid.
Since we know the molecular weights of both oleic acid (282g/mol) and I2
(254g/mol) we can establish a mass ratio on a per mol basis that we can
use to calculate how many grams of I2 will add across 100g of oleic acid.
In other words, if 1 mol of I2 adds to 1 mol of oleic acid, then 254g of I2 add
to 282 g of oleic acid. Thus, we can determine how many grams of I2
add to 100g of oleic using the following ratio:
254gI2 XgI2
=
282gOleic Acid 100gOleic Acid
(254gI2)(100gOleic Acid) = (XgI2)(282gOleic Acid)
X = 90gI2
meaning that 90g of I2 will add to 100g of oleic acid
65. Calculation of Iodine Value: Linoleic Acid (18:2Δ-9, 12)
CH3(CH2)4CH=CH-CH2-CH=CH(CH2)7COOH
For each mol of lipid, 1 mol of I2 will add across each double bond.
Therefore in the case of linoleic acid, with two double bonds, 2 moles of
I2 will add to 1 mol of linoleic acid.
The MW of linoleic acid is 280g/mol and the MW of I2 is 254g/mol. We can
establish the mass ratio to calculate how many grams of I2 will add
across 100g of linoleic acid. Remember that 2 moles of I2 add to 1 mol
of linoleic acid, so (254g/mol * 2 moles) of I2 add to (282 g/mol * 1 mol)
of linoleic acid.
66. Calculation of Iodine Value: Linoleic Acid (18:2Δ-9, 12)
CH3(CH2)4CH=CH-CH2-CH=CH(CH2)7COOH
For each mol of lipid, 1 mol of I2 will add across each double bond.
Therefore in the case of linoleic acid, with two double bonds, 2 moles of
I2 will add to 1 mol of linoleic acid.
The MW of linoleic acid is 280g/mol and the MW of I2 is 254g/mol. We can
establish the mass ratio to calculate how many grams of I2 will add
across 100g of linoleic acid. Remember that 2 moles of I2 add to 1 mol
of linoleic acid, so (254g/mol * 2 moles) of I2 add to (282 g/mol * 1 mol)
of linoleic acid.
508gI2 XgI2
=
280gLinoleic Acid 100gLinoleic Acid
67. Calculation of Iodine Value: Linoleic Acid (18:2Δ-9, 12)
CH3(CH2)4CH=CH-CH2-CH=CH(CH2)7COOH
For each mol of lipid, 1 mol of I2 will add across each double bond.
Therefore in the case of linoleic acid, with two double bonds, 2 moles of
I2 will add to 1 mol of linoleic acid.
The MW of linoleic acid is 280g/mol and the MW of I2 is 254g/mol. We can
establish the mass ratio to calculate how many grams of I2 will add
across 100g of linoleic acid. Remember that 2 moles of I2 add to 1 mol
of linoleic acid, so (254g/mol * 2 moles) of I2 add to (282 g/mol * 1 mol)
of linoleic acid.
508gI2 XgI2
=
280gLinoleic Acid 100gLinoleic Acid
(508gI2)(100gOleic Acid) = (XgI2)(280gOleic Acid)
X = 181gI2
68. Calculation of Iodine Value: Linoleic Acid (18:2Δ-9, 12)
CH3(CH2)4CH=CH-CH2-CH=CH(CH2)7COOH
For each mol of lipid, 1 mol of I2 will add across each double bond.
Therefore in the case of linoleic acid, with two double bonds, 2 moles of
I2 will add to 1 mol of linoleic acid.
The MW of linoleic acid is 280g/mol and the MW of I2 is 254g/mol. We can
establish the mass ratio to calculate how many grams of I2 will add
across 100g of linoleic acid. Remember that 2 moles of I2 add to 1 mol
of linoleic acid, so (254g/mol * 2 moles) of I2 add to (282 g/mol * 1 mol)
of linoleic acid.
508gI2 XgI2
=
280gLinoleic Acid 100gLinoleic Acid
(508gI2)(100gOleic Acid) = (XgI2)(280gOleic Acid)
X = 181gI2
meaning that 181g of I2 will add to 100g of linoleic acid
69. Lipid properties
• Saponification value
– Number of mg of potassium hydroxide required
to saponify with 1 gram of fat or oil
– 3 moles of KOH react with on mol of
triacylglycerol
70. Lipid properties
– If the triglyceride contains low molecular weight
fatty acids, the number of molecules present in a
1 gram sample of the fat will be greater than if
the fatty acids have long carbon chains and high
molecular weights
• The fat with the lower molecular weight fatty acids will
consequently have a higher saponification value
• Butter, for example, with a high percentage of butyric
acid, has a high saponification value
72. Modification of fats and oils
• Fats have the ability to enhance the
palatability of foods
• Because of this there is a great emphasis on
the crystallization and melting behavior of
fats
• Unique fatty acid distribution of some natural
fats makes them undesirable for certain
applications
73. Modification of fats and oils
– Physical characteristics are influenced by:
• Carbon chain length
– Increased chain length = increased melting point
• Degree of unsaturation
– The more unsaturated a fatty acid is, the more liquid it will be
at Troom
• Distribution of fatty acids on glycerol
monoglyceride diglyceride triglyceride
74. Modification of fats and oils
• Modified in order to change the solid fat
content (SFC) of lipids
– The fraction or percentage of a lipid that is solid
at a given temperature
– Enables less expensive lipids to be used
– Can reduce unsaturation, reducing susceptibility
to oxidation
– Can also increase unsaturation, potentially
increasing nutritional quality
75. Modification of fats and oils
• Common processes for modifying lipids
– Blending
– Dietary interventions
– Genetic manipulation
– Fractionation
– Interesterification
– Hydrogenation
76. Modification of fats and oils
• Interesterification
– Process used to improve the consistency of
some natural fats to enhance their usefulness
– Alteration of the original fatty acid distribution on
the glycerol backbone
• Affects melting and crystallization properties
• Rearrangement at random
77. Modification of fats and oils
– Process
• Rearrangement of fatty acids so that they become
distributed RANDOMLY among the TAG molecules
• Mixing of 2 esters resulting in the exchange of “R”
groups
O O
R1C – O – CH3 + R2C – O – C2H5
O O
R1C – O – C2H5 + R2C – O – CH3
78. Modification of fats and oils
• Occurs within TAG’s or between TAG’s
• Heat fat at high temperatures
• Use a catalyst to speed up the reaction
– Most popular: NaOCH3 (sodium methoxide)
– Alteration of physical properties of fats and oils
• Example: cocoa butter (mp 28 – 30ºC)
– Cocoa butter has a characteristic fatty acid composition and
distribution
» “Melts in your mouth, not in your hands”
– Once cocoa butter undergoes radomization by
interesterification, it no longer melts at the same temperature
79. Modification of fats and oils
Table 2. MP changes due to interesterification
Lipid MP (ºF) – Before MP (ºF) – After
Soybean oil 19.4 41.9
Cottonseed oil 50.9 93.2
Coconut oil 78.8 82.8
Palm oil 103.7 116.6
Lard 109.5 109.5
Tallow 115.2 112.3
40% hydrog. cottonseed oil 136.0 106.0
23% hydrog. palm oil 122.3 104.5
80. Modification of fats and oils
• Hydrogenation
– Very important to the oil industry
• Need to modify natural liquid oils to make fats with a
wide range of properties
– Soft and greasy to hard and brittle
• Usually only partial hydrogenation occurs
81. Modification of fats and oils
– Simple reaction
H H
- C = C - + H2 -C-C-
H H H H
• Addition of H2 across double bonds makes
compounds saturated
• Alters:
– Molecular configuration
– Number, geometry and location of double bonds
Most importantly, it can result in the formation of trans fatty
acids!!!
82. Modification of fats and oils
– Reasons for hydrogenation
• Convert liquid fats into plastic fats (suitable for
manufacture of shortenings and margarine)
• Improve resistance of fats and oils to deterioration
through oxidation or flavor reversion
• Convert soft fats into firmer fats
• Improve color
83. Modification of fats and oils
– General mechanism for hydrogenation
• Requires a catalyst
– Technically, it will happen naturally, however, the reaction
will take place VERY slowly
– Usually nickel
– Heterogeneous
» In other words, the catalyst is in a different chemical state
(typically solid when hydrogenating a liquid oil)
84. Modification of fats and oils
• Mechanism
CH2-CH=CH-CH2-
Absorption of fatty acid onto catalyst
Ni Ni
CH2-CH-CH-CH2- Double bond is broken and 2C-Ni bonds form
Reaction with absorbed H goes to partially hydrogenated
states
Ni Ni
CH2-CH2-CH-CH2- + CH2-CH-CH2 -CH2-
These may then go either of two ways
H desorption from catalyst Loses H from a C atom adjacent to a C-Ni bond
CH2-CH2-CH=CH- Double bond will
CH2-CH2-CH2-CH2- be cis or trans
Fully hydrogenated CH=CH-CH2-CH2- These fatty acids
can go back into
CH2-CH=CH-CH2- the cycle
85. Modification of fats and oils
– Rate of reaction depends on:
• Nature of substance being hydrogenated
– The greater the number of double bonds, the faster the
reaction
• Nature and concentration of the catalyst
• Concentration of H2
• Temperature, pressure and degree of agitation
– Increasing the temperature, pressure of H2 and degree of
agitation will all speed up the reaction
86. Modification of fats and oils
– If unlimited H2 at catalyst surface:
• Hydrogenation will be non-selective
– Selectivity: the tendency for more unsaturated fatty acids to
be reduced before those fatty acids that are more saturated
» Example: 18:3 are hydrogenated before 18:2 which are
hydrogenated before 18:1
• Any factor influencing the amount of H2 at the catalyst
surface will influence the rate and selectivity
• Control of selectivity
– Increase selectivity by reducing H2 at the catalyst surface
» Increase T, decrease P, increase amount of catalyst
87. Modification of fats and oils
– Partial hydrogenation (e.g. in soybean or
vegetable oil)
• In practice, partial hydrogenation is carried out in
vessels known as “converters”
• Closed, pressurized vessels with a capacity of
~60,000 pounds
• Agitation, heating, cooling and H2 inlet/vent systems
• Temperature ~ 175ºC
• Typical catalyst is Ni (0.01 – 0.02% of oil)
• H2 at 5 – 50 psi
• After partial hydrogenation, the oil is cooled, drained
and the catalyst is removed by filtration
88. Modification of fats and oils
– Testing partially hydrogenated oils
• Samples are analyzed for
– Iodine value
– Refractive index (AOCS method)
– Melting point
– Infrared spectroscopy (IR)
89. Polling question - hydrogenation
Which fatty acid would hydrogenate faster:
one with an IV of 103 or one with an IV
of 80?
90. Deterioration reactions
• Autoxidation
– General description
• Atmospheric oxidation of fats and oils
– General reaction characteristics
• Autocatalytic
• Has an induction point
• Accelerated by metals, light, and temperature
• Surface dependent
• Unsaturation dependent
• Produces a variety of oxidation products
91. Polling question - Autoxidation
Which of the following fatty acids is the most
susceptible to autoxidation:
A. Arachidic
B. Arachidonic
C. Palmitoleic
D. Myristic
92. Deterioration reactions
– Mechanism of lipid oxidation
• Free radical chain mechanism
• Initiation
Alkyl radical
RH R· + H·
– Removal of a H atom from a C adjacent to a double bond
– H atom is usually from the methylene group
– Example:
R-CH=CH-CH2-R’ R-CH=CH-C·H-R’
Methylene group
93. Deterioration reactions
• Propagation
– Alkyl radical (i.e. fatty acid free radical) combines with O2 to
first form peroxy radical
R· + O2 ROO· Peroxy radical: initial product during propagation
– Peroxy radical then combines with fatty acid to form
hydroperoxide and another alkyl radical
ROO· + RH ROOH + R·
Hydroperoxide
95. Deterioration reactions
– Primary product = hydroperoxide (peroxide)
• Measurement: peroxide value
– Problem: hydroperoxide decomposition
» Example: break down product = hexanal
Concentration
Hexanal
Time
» When measuring PV, the value rapidly
increases after lag period, but then decreases
as hydoperoxide decomposes
96. Deterioration reactions
– Induction period (i.e. lag period)
• No visible signs of oxidation occurring
– Doesn’t mean that oxidation isn’t occurring, though
• During the initiation phase
– Symbolizes reactants coming together
97. Deterioration reactions
– Antioxidants
• Function to interrupt the free-radical mechanism
– Extends the induction period
– Delays the onset of oxidative rancidity
• Limit on the amount of an antioxidant that can be used
– 0.02% of the weight of the fat
• Must be added at the beginning of a process to be
most effective
98. Deterioration reactions
– Initiation reaction
• Subject of great interest
– Common investigations: site of attack, energy requirements
• H atom adjacent to double bond is most susceptible
– Easy to remove because of neighboring double bond
• Unsure where 1st radical comes from in foods
– Perhaps singlet oxygen
– Trace metals may initiate the reaction (e.g. Cu, Fe)
99. Deterioration reactions
– Oxidation of monoenoic acids
• C8 and C11 are most likely sites for hydrogen removal
• They then react with O2 and attack another RH
resulting in hydroperoxide formation
• Hydroperoxide decomposes to aldehydes, alcohols
and ketones
• 4 free radicals/4 hydroperoxides
– Decompose
» Aldehyde production common
» Trace metals, temperature and light accelerate
hydroperoxide decomposition
100. Deterioration reactions
Oxidation of linoleic acid
9 10 11 12 13
-CH=CH-CH2-CH=CH-
Loss of proton
9 10 11 12 13
-CH=CH-CH-CH=CH-
Double bond shift for
isomerization
9 10 11 12 13 9 10 11 12 13
-CH-CH=CH-CH=CH- -CH=CH-CH=CH-CH-
O2, RH O2, RH
9 10 11 12 13 9 10 11 12 13
-CH-CH=CH-CH=CH- -CH=CH-CH=CH-CH-
Decomposition of
OOH Decomposition of hydroperoxide
OOH
O hydroperoxide O
10 11 12 13 13 14 15 16 17 18
9
C-CH=CH-CH=CH-(CH2)4-CH3 C-CH2-CH2-CH2-CH2-CH3
H 2, 4-decadienal H Hexanal
101. Deterioration reactions
– Aldehydes produced from various unsaturated fatty acids
• Oleic acid
Hydroperoxide Aldehyde formed
C8 2-undecenal
C9 2-decenal
C10 n-nonanol
C11 n-octanol
104. Deterioration reactions
– Nutritional implications of autoxidation
• Loss of β-carotene (provitamin A)
• Loss of fat-soluble vitamins (A, D, E, K)
• Loss of essential fatty acids
• Possible build up of polymeric material
• Loss of protein quality
– Free radicals will react with protein
– Carbonyl-amine reactions (i.e. Maillard browning reaction)
– Other implications
• Loss of color and flavor = shelf life limitations
• Warmed over flavors in refrigerated foods
105. Other deteriorative reactions
• Lipoxygenase reactions
– Enzyme catalyzed lipid oxidation
– Not the same mechanism as autoxidation
– Common reaction in soybeans
106. Other deteriorative reactions
• Lipolysis
– Hydrolysis reaction
• Water is involved
• Ester linkages can be broken by re-addition of water
produced when ester linkage is created
– Can occur due to enzymes, thermal stresses
(e.g. heat, moisture)
– Known as:
• Lipolysis, lipolytic rancidity, hydrolysis, hydrolytic
rancidity
DO NOT CONFUSE WITH OXIDATIVE RANCIDITY!!!
107. Other deteriorative reactions
• Lipolysis in heated fats – deep fat frying
– Usually at temperatures > 180ºC
– Results when oil is reused
– Moisture from food can cause hydrolysis (i.e.
lipolysis)
– Causes color changes (i.e. darkening) , an
increase in viscosity, a decrease in smoke
point, and potentially toxic products
108. Other deteriorative reactions
– Glycerol dehydration to acrolein (acrylaldehyde)
• Moisture from food escapes and causes oil to
hydrolyze into glycerol and free fatty acid(s)
Glycerol Acrolein
H H O
H-C-OH C
-H2O
H-C-OH C-H
Heat
H-C-OH C-H
H H
• Responsible for puffs of smoke
– Very pungent – choking irritating odor
• Results in smoke point depression
109. Other deteriorative reactions
• Thermal polymerization
– When a fat/oil is heated to a high temperature
(> 250ºC) in the absence of oxygen
– Also occurs during deep fat frying
110. Other deteriorative reactions
– Diels-Alder reaction
• A conjugate addition reaction of a conjugated
diene to an alkene (the dienophile) to produce a
cyclohexene
+
Conjugated Dienophile Cyclic
diene adduct
http://www.chem.ucalgary.ca/courses/351/Carey/Ch10/ch10-5.html
1, 3-butadiene Acrolein 1, 2, 3, 6 –tetrahydro benzaldehyde
CH2 H O
•Can cause
HC C CHO color and
+ viscosity
C-H changes
HC
•Also, can be
CH2 C-H carcinogenic
H
111. Antioxidants
• General definition
– Substances that slow or prevent oxidative
reactions that would result in undesirable
changes
• Examples: the development of off-flavors,
discoloration, and loss of nutritive value
– Antioxidants
– Synergists
– Oxygen displacers (e.g. inert gases)
– Protective coatings
112. Antioxidants
• Better definition
– Compound which prevents rapid oxidation of
food products by extending or prolonging the
induction period
114. Antioxidants
• Mechanism of antioxidant action
– Type I
• Primary antioxidants
• “Free radical chain stoppers”
– Interacts with free radicals produced during the initiation
phase (e.g. R· or ROO·)
• Normally phenolic (e.g. BHA, BHT)
OH H atom interacts with R· or ROO· to form RH or ROOH
115. Antioxidants
– Type II
• Inhibitors of free radical production in foods
• Examples: EDTA, citric acid, phosphates, and
phosphoric acid
– Tie up metal catalysts
116. Antioxidants
– Type III
• Elimination of environmental factors
• Examples:
– Lowering oxygen partial pressure in a package
» Vacuum, inert gas, airtight containers
– Lowering temperatures
» -12 to 20ºC
– Exclusion of light
– Prevention of contamination by catalytic, prooxidative metals
120. Antioxidants
• Major antioxidants used in foods
2 and 3-tert-butyl-4-hydroxyanisole butylated hydroxytoluene
propyl gallate
121. Antioxidants
• Growing interest in natural antioxidants
– Examples
• Tocopherols
– Principal antioxidant in vegetable oils
» Most widely distributed antioxidants in nature
– Example: vitamin E
122. Antioxidants
• Ascorbic acid (i.e. vitamin C)
– Works synergistically with vitamin E by regenerating it
123. Antioxidants
• Chelating agents
– Tie up metals
– Examples:
EDTA
Citric acid
124. Antioxidants
• Plant extracts
– Rosemary
» Fresh
» Not as effective as vitamin E, BHA, etc
– Soybean
– Honey
125. Antioxidants
• Popular misconceptions of antioxidants
– Improve flavor of poor quality fats and oils
– Improve oil in which oxidative ancidity has
developed
– Prevent microbial decay
– Prevent hydrolytic rancidity
126. References
Gunstone F. 1999. Fatty Acid and Lipid Chemistry.
Gaithersburg: Aspen Publishers, Inc.
McClements DJ and Decker EA. 2007. Lipids. In:
Fennema's Food Chemistry (4th Edition).
Damodaran S, Parkin KL, Fennema OR eds. Boca
Raton: CRC Press. P 155-212.
Nawar WW. 1996. Lipids. In: Food Chemistry (3rd
edition) Fennema OR, editor. New York: Marcel
Dekker, Inc. p 225-320.