5. Cis And Trans Fatty Acids
O
H H
CH3(CH2)7 C C (CH2)7 C OH
10 9
Cis 9 - Octadecenoic Acid (oleic)
O
H
CH3(CH2)7 C C (CH2)7 C OH
H
Trans 9 - Octadecenoic Acid (elaidic acid)
7. Naturally-occurring fatty acids
O
R CH2 CH CH CH2 CH CH CH2 C OH
7 6 5 4 3
1. Cis form
2. Not conjugated --- isolated double bond.
3. Even numbered fatty acids.
8. CLASSIFICATION OF FATTY ACIDS PRESENT
AS GLYCERIDES IN FOOD FATS
Systematic
Name
Formula Common source
I. Saturated Fatty Acids
Common
Name
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
9. 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
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
C19H31COOH traces in animal fats
10. 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
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
C19H31COOH traces in animal fats
11. Melting Points and Solubility in Water of Fatty Acids
Solubility in H O
Chain Length
2
Melting Point
13. Effects of Double Bonds on the Melting Points
F. A. M. P. (0C)
16:0
60
16:1 1
18:0 63
18:1 16
18:2 -5
18:3 -11
20:0 75
20:4 -50
M.P.
# Double bonds
14. FAT AND OILS
Mostly Triglycerides:
O
H2C OH
HC OH
H2C OH
O
HO C R
O
HO C R
O
HO C R
H2C O C R
O
HC O C R
O
H2C O C R
+
+ 3 H2O
Glycerol 3 Fatty Acids
15. GLYCERIDES
H2C OH
HC OH
H2C O
O
C (CH2)16CH3
H2C O
HC OH
H2C O
O
C (CH2)16CH3
O
C (CH2)16CH3
Monoglyceride (a - monostearin) Diglyceride (a, a' - distearin)
H2C O
HC O
H2C O
O
C (CH2)16CH3
O
C (CH2)14CH3
O
C (CH2)16CH3
(C18 )
(C16 )
(C18 )
Triglyceride (b - palmityl distearin)
16. a - oleodipalmitin
1 - oleodipalmitin
Oleic
Palmitic
Palmitic
OPP
a - Linoleyldiolein
1 - Linoleyldiolein
Linoleic
Oleic
Oleic
LOO
20. 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
24. Vitamin D2:
Vitamin E:
HO
H3C CH3
H3C
CH2
H
H
CH3
CH3
O
R1
R2
HO
R3
CH3
CH3
(CH2CH2CH2CH2)2CH2CH2CH2CH(CH3)2
25. 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
26. 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 56
Weight of Sample
= mg of KOH
27. 2. Saponification Value
Saponification - hydrolysis of ester under alkaline
condition.
O
O
C R
O
C R
O
C R
H2C O
HC O
H2C O
+ 3 KOH
+ 3 R C OK
H2C O
H
HC O
H
H2C O
H
28. 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
29. 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.
5. Conduct blank determination.
SP# =
56.1(B -S) x N of HCl
Gram of Sample
B - ml of HCl required by Blank.
S - ml of HCl required by Sample.
30. 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.
31. 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 CH
Cl I
ICl
+
Iodine chloride
Excess unreacted ICl
ICl KI KCl
I2
I2
+
Na2S2O3 Na2S4O6 NaI
+
+ 2 + 2
39. 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
40. Spectromertic 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
42. 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.
43. (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.
45. 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.
46. 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.
47. 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.
48. Pentane Formation from Linolenic Acid
14 13 12 11 10 9
CH3 (CH2)3 CH2 CH CH CH2 CH CH CH2 COOH
- .
12 11 10 9
CH3 (CH2)3 CH2 CH CH CH CH CH CH2 COOH
+
12 11 10 9
12 11 10 9
CH3 (CH2)3 CH2 CH CH CH CH CH CH2 COOH
+
_
+ .
12 11 10 9
12 11 10 9
+
O
O
.
H
.
CH3 (CH2)3 CH2 CH CH CH CH CH CH2 COOH
O
O
H
CH3 (CH2)3 CH2 CH CH CH CH CH CH2 COOH
O
Initiation (metal)
Propagation
Propagation
.
O2
H
OH .
Hydroperoxide
Decomposition
O
CH3 (CH2)3 CH2 H C CH CH CH CH C2H COOH
CH3 (CH2)3 CH3
.
H Termination .
Pentane
n
n
n
- n
n
n
49. ANALYSIS OF FLAVOR QUALITY & STABILITY OF OIL
1. Peroxide Value
O O
KI CH3 C OH HI CH3 C OK
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
50. 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.
51. 3. TBA Test.
To determine the rancidity degree of meat or fish product.
N
N
HS
OH
OH
C CH2 C
O
O
H
H
OH
OH
HS
N
N
OH
SH
N
N
HO
+
CH CH CH
H2O
Colored Pigment
+ 2