Lipid Lagi

LIPID Soluble in non-polar solvents and insoluble in polar solvents. Lipid is not polymers. Lipids: 1.

Fatty acids

2.

Neutral fats and oils

3.

Waxes

4.

Phospholipid

5.

Sterols

6.

Fat soluble vitamins

Fatty Acids O R C OH #1 Carbon

Acid Group

O R C OH

Polar End - Hydrophilic End

Non-polar End - Hydrophobic End (Fat-soluble tail)

Saturated Fatty Acids

8 5 3 7 4 6 2 CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2

Octanoic Acid

O 1 C OH

Unsaturated Fatty Acids 8 CH 3

7 CH 2

5 6 CH 2 CH 2

4 CH 2

3 2 CH 2 CH 2

O 1 C OH

3 - Octenoic Acid

8 7 CH 3 CH 2

5 3 4 6 2 CH 2 CH 2 CH 2 CH 2 CH 2 3, 6 - Octadienoic Acid

Short hand:

8:1 (∆3) 8:2 (∆3,6)

O 1 C OH

Cis And Trans Fatty Acids H

H CH 3 (CH 2 )7 C C (CH 2 )7 10 9

O C OH

Cis 9 - Octadecenoic Acid (oleic)

H CH 3 (CH 2 )7 C C (CH 2 )7

O C OH

H Trans 9 - Octadecenoic Acid (elaidic acid)

Polyunsaturated Fatty Acids Linoleic acid:

Cis, cis, 9, 12 - Octadecadienoic acid

Linolenic 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

Naturally-occurring fatty acids O R CH 2

CH CH CH 7

6

5

2

CH CH CH

4

3

1.

Cis form

2.

Not conjugated --- isolated double bond.

3.

Even numbered fatty acids.

2

C OH

CLASSIFICATION OF FATTY ACIDS PRESENT AS GLYCERIDES IN FOOD FATS Common Name

Systematic Name

Formula

Common source

I. Saturated Fatty Acids Butyric

Butanoic

CH3(CH2)2COOH

butterfat

Caproic

Hexanoic

CH3(CH2)4COOH

Caprylic

Octanoic

CH3(CH2)6COOH

Capric

Decanoic

CH3(CH2)8COOH

Lauric

Dodecanoic

CH3(CH2)10COOH

Myristic

Tetradecanoic CH3(CH2)12COOH

Palmitic

Hexadecanoic CH3(CH2)14COOH

Stearic

Octadecanoic

CH3(CH2)16COOH

Arachidic

Eicosanoic

CH3(CH2)18COOH

butterfat, coconut and palm nut oils coconut and palm nut oils, butterfat coconut and palm nut oils, butterfat coconut and palm nut oils, butterfat coconut and Palm nut oil, most animal and plant fats practically all animal and plant fats animal fats and minor component of plant fats peanut oil

Common Name

Systematic Name

Formula

Common source

II. Unsaturated Fatty Acids A. Monoethenoic Acids Oleic

Cis 9-octadecenoic

C17H33COOH

plant and animal fats

Elaidic

Trans 9-Octadecenoic

C17H33COOH

animal fats

C17H31COOH

peanut, linseed, and cottonseed oils

C17H29COOH

linseed and other seed oils peanut seed fats

B. Diethenoic Acids Linoleic

9,12-Octadecadienoic

C. Triethenoid Acids Linolenic

9,12,15-Octadecatrienoic

Eleostearic 9,11,13-Octadecatrienoic

C17H29COOH

D. Tetraethenoid Acids Moroctic Arachidonic

4,8,12,15Octadecatetraenoic 5,8,11,14-

C17H27COOH

fish oils

C19H31COOH

traces in animal fats

Common and Systematic Names of Fatty Acids Common Name

Systematic Name

Formula

Common source

A. Monoethenoic Acids Oleic

Cis 9-octadecenoic

C17H33COOH

plant and animal fats

Elaidic

Trans 9-Octadecenoic

C17H33COOH

animal fats

C17H31COOH

peanut, linseed, and cottonseed oils

C17H29COOH

linseed and other seed oils peanut seed fats

B. Diethenoic Acids Linoleic

9,12-Octadecadienoic

C. Triethenoid Acids Linolenic

9,12,15-Octadecatrienoic

Eleostearic 9,11,13-Octadecatrienoic

C17H29COOH

D. Tetraethenoid Acids Moroctic Arachidonic

4,8,12,15Octadecatetraenoic 5,8,11,14Eicosatetraenoic

C17H27COOH

fish oils

C19H31COOH

traces in animal fats

Melting Points and Solubility in Water of Fatty Acids

Melting Point

Solubility in H O 2 Chain Length

CHARACTERISTICS OF FATTY ACIDS Fatty Acids

M.P.(0C)

mg/100 ml Soluble in H2O

C4

-8

-

C6

-4

970

C8

16

75

C10

31

6

C12

44

0.55

C14

54

0.18

C16

63

0.08

C18

70

0.04

Effects of Double Bonds on the Melting Points F. A.

M. P. (0C)

16:0 16:1 18:0 18:1 18:2 18:3 20:0 20:4

60 1 63 16 -5 -11 75 -50

M.P.

# Double bonds

FAT AND OILS Mostly Triglycerides:

O

O H2C

OH

HC OH H2C

HO C O

OH

Glycerol

+

R

HO C R O HO C R

3 Fatty Acids

H2 C O C O HC

R

O C R O

H2 C O C

R

+ 3 H2O

GLYCERIDES O

H2 C OH HC OH O H2 C O C (CH 2 )16 CH 3 Monoglyceride (α - monostearin) H2 C O HC O H2 C O

H2 C O

C (CH 2 )16 CH 3

HC OH O H2 C O C (CH 2 )16 CH 3

Diglyceride (α, α' - distearin)

O C (CH 2 )16 CH 3 O C (CH 2 )14 CH 3 O C (CH 2 )16 CH 3

( C18 ) (C16 ) (C18 )

Triglyceride (β - palmityl distearin)

Oleic Palmitic

OPP

Palmitic

α - oleodipalmitin 1 - oleodipalmitin Linoleic Oleic

LOO

Oleic

α - Linoleyldiolein 1 - Linoleyldiolein

FATS AND OILS ARE PRIMARILY TRIGLYCERIDES (97-99%)

Vegetable oil - world supply - 68% Cocoa butter - solid fat Oil seeds - liquid oil Animal fat - 28% (from Hogs and Cattle) Marine oil - 4% Whale oil cod liver oil

Fatty Acids (%) of Fats and Oils Fatty Acids 4 6 8 10 12 14 16 16:1 18:0 18:1 18:2 18:3

Butter 3 3 2 3 3 10 26 7 15 29 2 2

Coconut Cottonseed

6 6 44 18 11 6 7 2

1 4 1 3 18 53

Soybean

12 2 24 54 8

MELTING POINTS OF TRIGLYCERIDES Triglyceride

Melting Point (°C)

C6

-15

C12

15

C14

33

C16

45

C18

55

C18:1 (cis)

-32

C18:1 (trans)

15

WAXES Fatty acids + Long chain alcohol Important in fruits: 3. Natural protective layer in fruits, vegetables, etc. 4. Added in some cases for appearance and protection. Beeswax (myricyl palmitate), Spermaceti (cetyl palmitate)

C30 H61

O O C C 15 H31

C16 H33

O O C C 15 H31

PHOSPHOLIPID Lecithin (phosphatidyl choline) O O

H2 C O C R

R C O CH

CH 3

O H2 C O P O CH 2 O_ Phosphatidic Acid

CH 2

+

N CH 3 CH 3 Choline

STEROLS Male & female sex hormones Bile acids Vitamin D Adrenal corticosteroids Cholesterol

21 H 3C 18

H 3C

HO

22 20

12 19 17 H3C 11 13 14 10 1 9 2 8 3 6 7 4 5

16 15

CH 3 CH 3

FAT SOLUBLE VITAMINS Vitamin A:

H3 C

CH3

CH 3 9

8

CH3

7

6

CH3

5 4

3

CH2OH 2

1

CH 3 H 3C H 3C

Vitamin D2: H

CH 3 CH 3

H CH 2

HO

Vitamin E: R1 R2 HO R3

CH 3 CH 3 O (CH 2 CH 2 CH 2 CH 2 )2 CH 2 CH 2CH 2 CH(CH 3 )2

ANALYTICAL METHODS TO MEASURE THE CONSTANTS 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

1. Acid Value Number of mgs of KOH required to neutralize the Free Fatty Acids in 1 g of fat.

ml of KOH x N x 56 = mg of KOH AV = Weight of Sample

2. Saponification Value Saponification - hydrolysis of ester under alkaline condition.

H2 C O HC O H2 C O

O C R O C R O C R

H 2 C OH +

3 KOH

HC O H H 2 C OH

O + 3 R C OK

Saponification Value of Fats and Oils Fat

Saponification #

Milk Fat

210-233

Coconut Oil

250-264

Cotton Seed Oil

189-198

Soybean Oil

189-195

Lard

190-202

2. Saponification Value Determination 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.

6.

Conduct blank determination. 56.1(B -S ) x N of HCl S P# = Gram of S ample

B - ml of HCl required by Blank. S - ml of HCl required by Sample.

3. Iodine Number

Number of iodine (g) absorbed by 100 g of oil.

Molecular weight and iodine number can calculate the number of double bonds. 1 g of fat adsorbed 1.5 g of iodine value = 150.

Iodine Value Determination Iodine Value = (ml of Na2S2O3 volume for blank - ml of Na2S2O3 volume for sample) × N of Na2S2O3 × 0.127g/meq × 100 Weight of Sample (g)

CH

CH

CH

+ ICl Iodine chloride

Cl

CH I

Excess unreacted ICl ICl I2 +

+

KI

2 Na2 S 2 O3

KCl

+

Na2 S 4 O6

I2 + 2 NaI

Iodine Numbers of Triglycerides Fatty Acids

# of Double-bonds

Iodine #

Palmitoleic Acid

1

95

Oleic Acid

1

86

Linoleic Acid

2

173

Linolenic Acid

3

261

Arachidonic Acid

4

320

Compositions (%) of Fatty Acids of Fats Fat

C4

C6 C10 C16 C18 C18:1 C18:2 C18:3 C20:4

1

5

5

20

40

2

20

35

3

10

50

4

20

40

40

5

10

20

20

6

30 40

5 40

10

20

20 100

4. GC Analysis for Fatty Acids 1.

Extract fat.

2.

Saponify (hydrolysis under basic condition).

3.

Prepare methyl ester (CH3ONa).

4.

Chromatography methyl ester.

5.

Determine peak areas of fatty acids. Fatty acids are identified by retention time.

6.

Compare with response curve of standard.

Fatty Acids Methyl Esters: Response 18:1

14

16

18

18:2

20

18:3

21:1 22

Time

GC condition: 10% DEGS Column (from supelco) Column temperature 200C.

24

5.

TRIGLYCERIDE ANALYSIS BY LIQUID CHROMATOGRAPHY Soybean Oil Solvent CH3CN/HF Column 84346 (Waters Associates)

RES PONS E

RETENTION TIME

Oleate-containing triglycerides in olive oil Fatty Acid Composition

Total Acyl Carbons: Unsaturation

Equivalent Carbon Number

OL2

54:5

44

O2L

54:4

46

OPL

52:3

46

O3

54:3

48

OSL

54:3

48

O2P

52:2

48

O2S

54:2

50

OPS

52:1

50

OS2

54:1

52

6. CHOLESTEROL DETERMINATION Enzymatic Determination: Cholesterol Oxidase

Cholesterol Oxidase HO

etc. + H2 O2

O

CH3O

H2 O2 +H2N

OCH3 NH2

CH3O

Peroxidase

HN

OCH3 NH

+ H2 O

0-Dianisidine

Oxidized 0-Dianisidine

(Colorless)

(Brown color)At 440 nm

Absorption at 440 nm

µg/ml Cholesterol

Cholesterol by GLC 1.

Prepare cholesterol butyrate.

2.

Analyze by GLC. time in GC - 15 min. sensitivity - 10-7 g.

Spectromertic Absorption Standard Curve of Cholesterol

Absorption at 440 nm

µg/ml Cholesterol

Cholesterol by GLC 1.

Prepare cholesterol butyrate.

2.

Analyze by GLC. time in GC - 15 min. sensitivity - 10-7 g.

LIPID CONTENT ANALYSES 1.

Gravimetric Method (1) Wet extraction - Roese Gottliegb & Mojonnier. (2) Dry extraction - Soxhlet Method.

2.

Volumetric Methods (Babcock, Gerber Methods)

1. Gravimetric Method (1) Wet Extraction - Roese Gottlieb & Mojonnier.

For Milk: 1) 10 g milk + 1.25 ml NH4OH mix. solubilizes protein and neutralizes. 2) + 10 ml EtOH - shake. Begins extraction, prevents gelation of proteins. 3) + 25 ml Et2O - shake and mix. 4) + 25 ml petroleum ether, mix and shake.

(2) Dry Extraction - Soxhlet Method.

Sample in thimble is continuously extracted with ether using Soxhlet condenser. After extraction, direct measurement of fat - evaporate ether and weigh the flask.

Indirect measurement - dry thimble and weigh thimble and sample.

Soxhlet Method.

2. Volumetric Method (Babcock, Gerber Methods) Theory: 2. Treat sample with H2SO4 or detergent. 3. Centrifuge to separate fat layer. 4. Measure the fat content using specially calibrated bottles. Methods: 1. Known weight sample. 2. H2SO4 - digest protein, liquefy fat. 3. Add H2O so that fat will be in graduated part of bottle. 4. centrifuge to separate fat from other materials completely.

REACTIONS OF FATS Hydrolytic Rancidity:

1. Triglyceride -> Fatty acids Specially C4 butyric acid (or other short chain fatty acids) are the real problem.

2. By lipase.

LIPID OXIDATION Major flavor problems in food during storage are mainly due to the oxidation of lipid.

Lipid Oxidation - free radical reactions. 1.

Initiation.

2.

Propagation.

3.

Termination.

Pentane Formation from Linolenic Acid 14

CH 3 (CH 2 )3

CH 2

13

12

11

Initiation (metal)

12

11

CH 2

11

.

9 2

n COOH

10

9 2

nCOOH

2n

COOH

+ H.

O

11

10

9

CH 2 CH CH CH CH CH - CH O

Hydroperoxide Decomposition

O

_

H

(CH 2 )3

10

CH CH CH CH CH CH

12

CH 3

COOH

O

Propagation

(CH 2 )3

n

+ O2 12

CH 3

2

CH 2 CH CH CH CH CH CH

Propagation CH 3 (CH 2 )3

CH CH CH

2

- H.

.

CH 3 (CH 2 )3

9

10

CH CH CH

CH 2

12

.OH 11

10

9

CH CH CH CH CH CH

.

2n

COOH

O

CH 3 (CH 2 )3

. CH 2

O

12

11

10

9

+ H C CH CH CH CH CH

.

Termination

+ H CH 3

(CH 2 )3 Pentane

CH 3

2n

COOH

ANALYSIS OF FLAVOR QUALITY & STABILITY OF OIL 1.

Peroxide Value O

O

A.

KI + CH 3

B.

ROOH + 2 HI

I2 +

C.

I2 + 2 Na2 S 2 O3

2 NaI +

C

OH

Peroxide Value = (milliequivalent peroxide/kg of sample)

HI

+ CH 3

H2O +

C

ROH

Na2 S4 O6

ml of Na2S2O3 × N × 1000 Grams of Oil

OK

2. Active Oxygen Method (AOM) Determined the time required to obtain certain peroxide value under specific experimental conditions. The larger the AOM value, the better the flavor stability of the oil.

3. TBA Test. To determine the rancidity degree of meat or fish product. HS

N

OH

O +

N

H

O C CH 2

C H

OH

HS

N N OH

OH CH

HO CH

CH

Colored Pigment

N

SH N

OH

+ 2 H2O