Transcript Oils and Fats

Oils and Fats
Major Component (%95-99)
Minor Components (%1-5)
Triglycerides
Triglyceride Derivatives
Non-Triglyceride Derivatives
Glycerol
Phospholipids
Free Fatty Acids
Sterols
Mono- and Diglycerides
Pigments
Vitamins
Antioxidants
Oxidation Products
Trace Metals
Hydrocarbons
Triglyceride Structure
H2C
OH
3 fatty acids
O
O
O C - R1
O
O HO - C - R1
HC OH +
= HC O C- R2 +3H20
HO - C - R2
O
H2C OH
O
glycerol
H2C O C - R3
HO - C - R3
triacylglycerol
H2C
–One chiral carbon with 1-3 acyl groups
–simpler stereochemistry than sugars
-C
–more possible substituents
O
R acyl
Triglycerides differ from each other in
regard to
• Number of Carbon Atoms in fatty acid
chains
• Number of double bonds
• Isomerization
• Distribution of FA on glycerol backbone
Analytical Methods
• Saponification Value
• Iodine Value
• Gas Chromatographic Analysis for Fatty
Acids
• Liquid Chromatography
Saponification Value
Saponification - hydrolysis of ester under alkaline
condition.
The saponification value of an oil or fat is defined
as the number of mg of potassium hydroxide
(KOH) required to neutralize the fatty acids
resulting from the complete hydrolysis of 1 g of
the sample.
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 (0.5 N) in Erlenmeyer.
3.
Boil for saponification.
4.
Titrate with HCl (0.5 N) using phenolphthalein.
5.
Conduct blank determination.
SP # =
56.1(B -S) x N of HCl
Gr am of Sample
B - ml of HCl required by Blank.
S - ml of HCl required by Sample.
N- Factor of 0.5 N HCL.
Saponification Value
O
O C- R
O
HC O C- R +
O
H2C O C - R
triacylglycerol
H2C
3 K+OH -
H2C
OH
HC
OH
O
+
H2C OH
glycerol
3 KO -
C-R
Potassium salt
Similarly;
RCOOH
+
KOH
RCOO-K+
+
Glycerol
MG
+
KOH
RCOOK
+
Glycerol
DG
+
2KOH
2RCOOK
+
Glycerol
Saponification Value
1 mol TG
1 g TG
3 mol KOH required
X mol KOH required
MWKOH: 56 g = 56000 mg
1 g TG : 1 g / MWTG (g/mol) mol
1 mol TG
3x 56000 mg KOH required
1 g TG / MWTG
X mg KOH required
168000
X  SN 
MWTG
Saponification Value
168000
X  SV 
MWTG
• What is the MWTG ?
H2C
HC
H2C
O
O
O C- R
O
O C- R
O
O C-R
O C - R1
O
O C- R1
O
O C - R2
H2C
HC
H2C
O
H2C
HC
H2C
O C - R1
O
O C- R2
O
O C - R3
Saponification Value
168000
X  SV 
MWTG
• Which one’s MW should be taken?
H2C
HC
H2C
O
O
O C- R
O
O C- R
O
O C-R
O C - R1
O
O C- R1
O
O C - R2
H2C
HC
H2C
O
H2C
HC
H2C
O C - R1
O
O C- R2
O
O C - R3
Saponification Value
168000
X  SV 
AMWTG
• The Answer is the Weighted Average MW
H2C
HC
H2C
O
O
O C- R
O
O C- R
O
O C-R
O C - R1
O
O C- R1
O
O C - R2
H2C
HC
H2C
O
H2C
HC
H2C
O C - R1
O
O C- R2
O
O C - R3
Saponification Value
Calculation of AMWTG
Oil consists of only type Simple Triglyceride
O
H2C
HC
H2C
O C- R
O
O C- R
O
O C-R
AMWTG  41 3  (MWFAR - 1)
Saponification Value
Calculation of AMWTG
Oil consists of Simple and Mixed type Triglyceride with
two fatty acids R1 (%90 w/w) and R2 (%10 w/w)
O
O
O
O
H2C
O C - R1
O
H2C
O C - R1
O
H2C
O C - R2
O
H2C
O C - R1
O
HC
O C- R1
O
HC
O C- R1
O
HC
O C- R2
O
HC
O C- R2
O
H2C
O C - R1
H2C
O C - R2
H2C
O C - R2
H2C
O C - R2
AMWTG  41 3  [(x R1  MWFAR1  x R 2  MWFAR 2 ) -1]
Average Moleculer Weight of FAs
in Oil (AMWFA)
Saponification Value
Generalized Calculation of AMWTG
Oil consists of Simple and Mixed type Triglyceride with N
fatty acids
FA
R1
R2
.
.
RN
AMWTG  41 3  [(
xi
x1
x2
.
.
xN

N
i 1
x R i  MWFAR i ) - 1]
Saponification Value
168000
SV 

AMWTG 41  [3  (
Fat
168000

N
i 1
x R i  MWFA R i  1)]
SV
Milk Fat
210-233
Coconut Oil
250-264
Cotton Seed Oil
189-198
Soybean Oil
189-195
Lard
190-202
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
18:2
18
18:3
20
21:1
22
T im e
GC condition: 10% DEGS Column (from supelco)
Column temperature 200C.
24
TRIGLYCERIDE ANALYSIS BY
LIQUID CHROMATOGRAPHY
Soybean Oil
Solvent CH3CN/HF
Column ODS- Octadesilsilan (C:18)
RESP ONSE
RET ENT I ON T I ME
Iodine Number
• The iodine value of an oil or fat is defined as the mass of iodine absorbed by
100 g of the sample.
•
The unsaturated fatty acid residues of the glycerides react with iodine, and
thus the iodine value indicates the degree of unsaturation of the fatty acid
residues of the glycerides.
• It is constant for a particular oil or fat, but depends on the method used.
Animal fats (butter, dripping, lard) 30 - 70 Iodine Value
• Non-drying oils (olive, almond) 80 - 110 Iodine Value
• Semi-drying oils (cottonseed, sesame, soya) 80 - 140 Iodine Value
• Drying oils (linseed, sunflower) 120 - 200 Iodine Value
• The iodine value is often most useful in identifying the source of an oil.
Generally, the higher iodine values indicate oils and the lower values fats.
Iodine values are normally determined using Wigs or Hanus methods.
Determination of Iodine Number
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
Cl
+ ICl
Iodine chloride
CH
I
Excess unreacted ICl
I Cl
I2 +
+
KI
2 Na2 S2 O3
KCl
+
Na2 S4 O6
I2
+ 2 NaI
Theoretical Iodine Value
• Monoene + I2
• Diene + 2*I2
• Triene +3* I2
Saturated
Saturated
Saturated
Assumption: Oil =TG
Sample: 100 g basis
FA
C16:0
C18:0
C18:1
C18:2
C18:3
C20:0
xi
5
15
15
40
1
3
Theoretical Iodine Value
1 mol C18:1
15 g C18:1
1 mol I2 (254 g)
X (g) I2
15 254
IVC18:1 
282
1 mol C18:2
40 g C18:2
IVC18:2
Assumption:
Oil =TG
FA
C16:0
C18:0
C18:1
C18:2
C18:3
C20:0
2 mol I2 (2x254 g)
X (g) I2
40 2  254

280
xi
5
15
15
40
1
3
Theoretical Iodine Value
1 mol C18:3
1 g C18:3
3 mol I2 (3x254 g)
X (g) I2
IVC18:3
1 3  254

276
Theoritical IV= IV C18:1 + IV C18:2+ IV C18:2
Real IV= 0.95xTheoricital Value