Lipid more than sufficient
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Transcript of Lipid more than sufficient
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
Non-polar End - Hydrophobic End (Fat-soluble tail)
Polar End - Hydrophilic End
Saturated Fatty Acids CH3 CH2 CH2 CH2 CH2 CH2 CH2 C OH
O1245678 3
Octanoic Acid
Unsaturated Fatty Acids CH3 CH2 CH2 CH2 CH2 CH2 CH2 C OH
O1245678 3
CH3 CH2 CH2 CH2 CH2 CH2 CH2 C OH
O1245678 3
3 - Octenoic Acid
3, 6 - Octadienoic Acid
Short hand: 8:1 (3)
8:2 (3,6)
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
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 R CH2 CH CH CH2 CH CH CH2 C OH
O
7 6 5 4 3
1. Cis form
2. Not conjugated --- isolated double bond.
3. Even numbered fatty acids.
CLASSIFICATION OF FATTY ACIDS PRESENT AS GLYCERIDES IN FOOD FATS
I. Saturated Fatty Acids
Butyric Butanoic CH3(CH2)2COOH butterfat
Caproic Hexanoic CH3(CH2)4COOH butterfat, coconut and palm nut oils
Caprylic Octanoic CH3(CH2)6COOH coconut and palm nut oils, butterfat
Capric Decanoic CH3(CH2)8COOH coconut and palm nut oils, butterfat
Lauric Dodecanoic CH3(CH2)10COOH coconut and palm nut oils, butterfat
Myristic Tetradecanoic CH3(CH2)12COOH coconut and Palm nut oil, most animal and plant fats
Palmitic Hexadecanoic CH3(CH2)14COOH practically all animal and plant fats
Stearic Octadecanoic CH3(CH2)16COOH animal fats and minor component of plant fats
Arachidic Eicosanoic CH3(CH2)18COOH peanut oil
Common Name
Systematic Name
Formula Common source
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
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
oilsEleostearic 9,11,13-Octadecatrienoic C17H29COOH peanut seed fats
D. Tetraethenoid Acids
Moroctic4,8,12,15-Octadecatetraenoic
C17H27COOH fish oils
Arachidonic 5,8,11,14-Eicosatetraenoic
C19H31COOH traces in animal fats
Common and Systematic Names of Fatty AcidsCommon 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
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
oilsEleostearic 9,11,13-Octadecatrienoic C17H29COOH peanut seed fats
D. Tetraethenoid Acids
Moroctic4,8,12,15-Octadecatetraenoic
C17H27COOH fish oils
Arachidonic 5,8,11,14-Eicosatetraenoic
C19H31COOH traces in animal fats
Melting Points and Solubility in Water of Fatty Acids
Solubility in H O
Chain Length
2
Melting Point
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.(0C) mg/100 ml Soluble in H2O
C18 70 0.04
CHARACTERISTICS OF FATTY ACIDS
Effects of Double Bonds on the Melting Points
16:0
6016:1 118:0 6318:1 1618:2 -518:3 -1120:0 75
F. A. M. P. (0C)
20:4 -50
M.P.
# Double bonds
FAT AND OILS
Mostly 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
GLYCERIDES
Monoglyceride ( - monostearin) Diglyceride (' - distearin)
H2C OH
HC OH
H2C O
O
C (CH2)16CH3
H2C O
HC OH
H2C O
O
C (CH2)16CH3
C (CH2)16CH3
O
Triglyceride ( - palmityl distearin)
H2C O
HC O
H2C O
O
C (CH2)16CH3
C (CH2)16CH3
O
O
C (CH2)14CH3
( C18)
(C16)
(C18)
- oleodipalmitin
1 - oleodipalmitin
Oleic
Palmitic
Palmitic
OPP
- Linoleyldiolein
1 - Linoleyldiolein
Oleic
Linoleic
OleicLOO
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
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
MELTING POINTS OF TRIGLYCERIDES
C6 -15
C12 15
C14 33
C16 45
C18 55
C18:1 (cis) -32
Triglyceride Melting Point (°C)
C18:1 (trans) 15
WAXES
Fatty acids + 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
C16H33 O C C15H31
PHOSPHOLIPID
Lecithin (phosphatidyl choline) O
O
H2C O C RO
R C O CH
H2C O P O CH2 CH2 N+ CH3
CH3
CH3
O_
Phosphatidic Acid Choline
STEROLS
Male & female sex hormones
Bile acids
Vitamin D
Adrenal corticosteroids
Cholesterol HO
H3C
H3C
H3C CH3
CH3
123 4 5
6 789
10
1112
1314 15
1617
18
21 22
19
20
FAT SOLUBLE VITAMINS
Vitamin A: CH2OH
CH3 CH3
CH3
CH3H3C
12
34
5
67
89
Vitamin D2:
Vitamin E:
HO
CH2
HH
H3C
H3C CH3
CH3
CH3 O
R1
R2
HO
R3
CH3(CH2CH2CH2CH2)2CH2CH2CH2CH(CH3)2
CH3
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.
AV = ml of KOH x N x 56Weight of Sample
= mg of KOH
2. Saponification Value
Saponification - hydrolysis of ester 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 OK+ 3 + 3
Milk Fat 210-233
Coconut Oil 250-264
Cotton Seed Oil 189-198
Soybean Oil 189-195
Fat
Saponification #
Lard 190-202
Saponification Value of Fats and Oils
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.
B - ml of HCl required by Blank.
S - ml of HCl required by Sample.
SP# = 56.1(B -S) x N of HCl
Gram of Sample
2. Saponification Value Determination
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 = (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 CH
Cl I
ICl
Iodine chloride
+ ICl KI KCl
I2
I2
Na2S2O3 Na2S4O6 NaI
+
+ 2 2+
+
Excess unreacted ICl
Iodine Value Determination
Iodine Numbers of Triglycerides
Palmitoleic Acid 1 95
Oleic Acid 1 86
Linoleic Acid 2 173
Linolenic Acid 3 261
Fatty Acids # of Double-bonds Iodine #
Arachidonic Acid 4 320
Compositions (%) of Fatty Acids of Fats
1 5 5 20 40 30
2 20 35 40 5
3 10 50 40
4 20 40 40
5 10 20 20 10 20 20
Fat C4 C6 C10 C16 C18 C18:1 C18:2 C18:3 C20:4
6 100
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:
14
18:1
18:2 2018:3
22
21:1 2416 18
Time
Response
GC condition: 10% DEGS Column (from supelco)
Column temperature 200C.
5. TRIGLYCERIDE ANALYSIS BY LIQUID CHROMATOGRAPHY
Soybean Oil
Solvent CH3CN/HF
Column 84346 (Waters Associates)
RESPONSE
RETENTION TIME
Oleate-containing triglycerides in olive oil
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
Fatty Acid Composition
Total Acyl Carbons: Unsaturation
Equivalent Carbon Number
OS2 54:1 52
6. CHOLESTEROL DETERMINATION
Enzymatic Determination: Cholesterol Oxidase HO O
H2O2
Cholesterol Oxidaseetc. +
H2O2
CH3O OCH3
H2N NH2 HN NH
OCH3CH3O
H2OPeroxidase+ +
0-Dianisidine Oxidized 0-Dianisidine
(Colorless) (Brown color)At 440 nm
Cholesterol by GLC
1. Prepare cholesterol butyrate.
2. Analyze by GLC.
time in GC - 15 min.sensitivity - 10-7 g.
g/ml Cholesterol
Absorption at 440 nm
Spectromertic Absorption Standard Curve of CholesterolSpectromertic Absorption Standard Curve of Cholesterol
Cholesterol by GLC
1. Prepare cholesterol butyrate.
2. Analyze by GLC.
time in GC - 15 min.sensitivity - 10-7 g.
g/ml Cholesterol
Absorption at 440 nm
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:
1. Treat sample with H2SO4 or detergent.
2. Centrifuge to separate fat layer.
3. 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 +
+
_
.+
.-
+
CH3 (CH2)3 CH2 CH CH CH CH CH CH2 COOH
CH3 (CH2)3 CH2 CH CH CH2 CH CH CH2 COOH
.
H
.
CH3 (CH2)3 CH2 CH CH CH CH CH CH2 COOH
O
O
H
O
O
CH3 (CH2)3 CH2 CH CH CH CH CH CH2 COOH
CH3 (CH2)3 CH2 CH CH CH CH CH CH2 COOH
O
Initiation (metal)
Propagation
Propagation.
O2
H
OH.HydroperoxideDecomposition
CH3 (CH2)3 CH2 H C CH CH CH CH CH2 COOH
CH3 (CH2)3 CH3
O.
H.Termination
Pentane
14 13 12 11 10 9
12 11 10 9
12 11 10 9
12 11 10 9
12 11 10 9
12 11 10 9
n
n
n
- n
n
n
ANALYSIS OF FLAVOR QUALITY & STABILITY OF OIL
1. Peroxide Value
KI CH3 C OH HI CH3 C OK
O O
ROOH HI I2 H2O ROH
I2 Na2S2O3 NaI Na2S4O6
A.
B.
C.
+
+
+
+
+
+
+
2
2
2
Peroxide Value = ml of Na2S2O3 N 1000
(milliequivalent peroxide/kg of sample) Grams of Oil
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. N
N
HS
OH
OH
C CH2 C
O
H
O
H
OH
OH
HS
N
N
OH
SH
N
N
CH CH CH
HO
H2O
Colored Pigment
+
+ 2