chemistry of fats & oils

8/2/2019 Chemistry of Fats & Oils

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CHEMISTRYCHEMISTRY

OFOF

OILS AND FATSOILS AND FATS


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DefinitionDefinition

A group of substances that in generalA group of substances that in general

are soluble in organic solvents, but areare soluble in organic solvents, but are

not soluble in water are called lipids.not soluble in water are called lipids.

Oils & Fats are one class of lipid.Oils & Fats are one class of lipid.

They can be used for edible as well asThey can be used for edible as well as

non-edible purposes.non-edible purposes.


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Roles of Food LipidsRoles of Food Lipids

Energy Source

Source of essential fatty acids

Carrier of Fat Soluble Vitamins

Main Flavor Source of Foods

Regulates Hormone and Cell StructureHelp to Develop Nervous System

Build adipose tissues which cause ThermalInsulation of Body

Mouth Feeling

Texture of Foods

Emulsifying Agents

Mold Releasing and Anti-spattering Agent


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Source of Food LipidsSource of Food LipidsPlant source seeds, grains, fruits, brans etc.Animal source milk, egg, tallow, lard, microbial

etc.

Marine source fish and other animals.World Supply

Vegetable oil 68%

Animal fat 28%

Marine oil - 4%


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1. Fatty acids

2. Neutral fats and oils or triglycerides

3. Monoglycerides and diglycerides

4. Waxes

5. Phospholipids

6. Sterols

Types of Lipids


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Composition of fats and oilsComposition of fats and oils

Fatty acid esters of glycerol i.e.

triglycerides

Triglycerides which is liquid at room

temperature are termed as oils and those

solids are termed as fats


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Triglycerides

O

H2C OH

HC OH

H2C OH

HO C R

HO C R

HO C R

O

O

O

H2C O C RO

O

H2C O C R

HC O C R+

+ 3 H2O

Glycerol 3 Fatty Acids


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Saturated and Unsaturated Fatty AcidsSaturated and Unsaturated Fatty Acids


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Cis 9 - Octadecenoic Acid (oleic)

Trans 9 - Octadecenoic Acid (elaidic acid)

O

CH3(CH2)7 C C (CH2)7 C OH

HH

910

O

CH3(CH2)7 C C (CH2)7 C OH

H

H

Cis And Trans Fatty Acids


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Polyunsaturated Fatty Acids

Linoleic acid: Cis, cis, 9, 12 - Octadecadienoic acidLinolenic acid: Cis, cis, cis 9, 12, 15 - Octadecatrienoic

acid

Arachidonic acid: Cis, cis, cis, cis 5, 8, 11, 14 -Eicosatetraenoic acid

Linoleic Acid

Linolenic Acid

Arachidonic Acid


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Fatty AcidsMelting Points and Solubility in Water

Solubility in H O

Fatty Acid Chain Length

2

Melting Point

zx

x

x

x

x

x

x

x

MeltingPoin

t


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Effects of Double Bonds on the Melting Points

M.P.

# Double bonds

x

x

xx


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DIFFERENT TYPES OF GLYCERIDES

Monoglyceride ( - monostearin) Diglyceride (, ' - distearin)

H2C OHHC OH

H2C O

O

C (CH2)16 CH3

H2C O

HC OH

H2C O

O

C (CH2)16 CH3

C (CH2)16 CH3

O

Triglyceride ( - palmityl distearin)

H2C O

HC O

H2C O

O

C (CH2)16 CH3

C (CH2)16 CH3

O

O

C (CH2)14 CH3

( C18 )

(C16 )

(C18 )


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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

18:3 2 - - 8

C


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Phospholipid

Lecithin (phosphatidyl choline)

O

O

H2C O C RO

R C O CH

H2 C O P O CH2 CH2 N

+

CH3

CH3

CH3

O_

Phosphatidic Acid Choline


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Other phospholipids are :

Phophatidyl ethanol amine

Phosphatidyl serine

Phosphatidyl inositol

Cardiolipin


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Esters of Fatty acid and Long chain alcohol

WAXES

OC30H61 O C C15H31

O

C16H33 O C C15H31


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Sterols

Plant sterols or PHYTOSTEROLS

Animal Sterols or CHOLESTEROLS


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Phytosterol


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Cholesterol

HO

H3C

H3

C

H3C CH 3

CH 3

1

234

56 78

910

11

12

1314

15

1617

18

2122

19

20


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Characteristic Components PresentCharacteristic Components Present

on Some Special Oilon Some Special Oil

Lignans in sesame oil;

Oryzanol in rice bran oil;

Gossypol in cottonseed oil;Cholesterol in butter as well as in animal fat;

Hydroxy fatty acid in Castor oil;

Cyclic acid in Sal fat;

Trans fatty acid in Vanaspati


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Non-lipid component present in

Oils & FatsFat soluble vitamins

Pigments


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Some important parameters to

Characterize Fats and Oils


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1. Acid Value

2. Saponification Value

3. Iodine Value

4. Peroxide Value

5. Gas Chromatographic Analysis for Fatty Acidcomposition

6. Liquid Chromatography for triglyceride composition

Analytical Methods


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Acid Value

Number of mgs of KOH required to neutralize the Free

Fatty Acid present in 1 g of oil/fat.

Fatty acid generate due to hydrolytic rancidity

Triglyceride Fatty acids

RCOOH + KOH ROO- K+ + H2O

AV = (56.1 x N x V)/ wt. of sample

Moisture/

Lipase


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Saponification Value

Saponification - Hydrolysis of ester (triglyceride) under

alkaline condition. It gives the idea about the average

molecular weight of fatty acid present in particular oil/fat.

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 + 3

Heat

Definition : mgs of KOH required to saponify 1 g of fat

SP# =56.1(B -S) x N of HCl

Gram of Sample


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Iodine Value

gms of iodine absorbed by 100 g of oil.

Iodine number indicates the amount of

unsaturation in fats and oils.

Iodine Value = (ml of Na2S2O3 volume for blank -

ml of Na2S2O3 volume for sample) N ofNa2S2O3 0.127g/meq 100

Weight of Sample (g)


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Peroxide Value

It indicates about the amount of primary oxidationproducts present in Oil/Fat.

Peroxide Value = ml of Na2S2O3 Normality 1000

Grams of Oil

Unit : (mill equivalent /kg)


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GC Analysis for Fatty Acids

1. Extract fat.

2. Saponify (hydrolysis under basic condition).

3. Prepare methyl ester (by BF3-methanol/CH3ONa).

4. Inject methyl ester in GC

5. Determine peak areas of fatty acids.

(Fatty acids are identified by relative retention time)

6. Compare with response curve of standard.


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Chromatogram of Fatty Acids Methyl

Esters

14

18:1

18:2 2018:3

22

21:1 2416

18

Time

Resp

onse

GC condition: 10% DEGS Column (from supelco)

Column temperature 200C.


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TAG Composition

Triglyceride composition (e.g. S3, S2U, SU2 or

U3) of oil/fat can be determined by HighPerformance Liquid Chromatography (HPLC)

In this chromatography, oil samples can beinjected directly.


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Soxhlet Method


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Fat Soluble Vitamins

Vitamin A

CH2OH

CH3 CH3

CH3

CH3H3C

12

34

5

67

8

9


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Vitamin D2

Vitamin E

HO

CH 2

HH

H3C

H3C CH 3

CH 3

CH 3

O

R1

R2

HO

R3

CH3(CH2CH2CH2CH2)2CH2CH2CH2CH(CH3)2

CH3


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Pigments

-Carotene and Chlorophyll (green)
http://upload.wikimedia.org/wikipedia/commons/d/da/Beta-carotene.png


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Chlorophyll

chemistry of fats & oils

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