Oils and Fats

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Oils and Fats
Major Component (95-99) Triglycerides
Minor Components (1-5)
Triglyceride Derivatives Glycerol Free Fatty
Acids Mono- and Diglycerides
Non-Triglyceride Derivatives Phospholipids Sterols
Pigments Vitamins Antioxidants Oxidation
Products Trace Metals Hydrocarbons
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Triglyceride Structure
3H20
acyl
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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

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Analytical Methods

• Saponification Value
• Iodine Value
• Gas Chromatographic Analysis for Fatty Acids
• Liquid Chromatography

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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.

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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.
• Conduct blank determination.
• B - ml of HCl required by Blank.
• S - ml of HCl required by Sample.
• N- Factor of 0.5 N HCL.

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Saponification Value
3
3 KOH -

Potassium salt
Similarly
RCOOH KOH RCOO-K
Glycerol MG KOH RCOOK
Glycerol DG
2KOH 2RCOOK Glycerol
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Saponification Value

• 1 mol TG 3 mol KOH required
• 1 g TG 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

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Saponification Value

• What is the MWTG ?

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Saponification Value

• Which ones MW should be taken?

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Saponification Value

• The Answer is the Weighted Average MW

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Saponification Value

• Calculation of AMWTG
• Oil consists of only type Simple Triglyceride

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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)

Average Moleculer Weight of FAs in Oil (AMWFA)
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Saponification Value

• Generalized Calculation of AMWTG
• Oil consists of Simple and Mixed type
  Triglyceride with N fatty acids

FA xi R1 x1 R2 x2 . . . . RN xN
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Saponification Value
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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.

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Fatty Acids Methyl Esters
GC condition 10 DEGS Column (from
supelco) Column temperature 200C.
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TRIGLYCERIDE ANALYSIS BY LIQUID CHROMATOGRAPHY
Soybean Oil Solvent CH3CN/HF Column ODS-
Octadesilsilan (C18)
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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.

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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)
Excess unreacted ICl
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Theoretical Iodine Value

• Monoene I2 Saturated
• Diene 2I2 Saturated
• Triene 3 I2 Saturated
• Sample 100 g basis

Assumption Oil TG FA xi C160 5 C180 15 C181 1
5 C182 40 C183 1 C200 3
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Theoretical Iodine Value

• 1 mol C181 1 mol I2 (254 g)
• 15 g C181 X (g) I2
• 1 mol C182 2 mol I2 (2x254 g)
• 40 g C182 X (g) I2

Assumption Oil TG FA xi C160 5 C180 15 C181 1
5 C182 40 C183 1 C200 3
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Theoretical Iodine Value

• 1 mol C183 3 mol I2 (3x254 g)
• 1 g C183 X (g) I2

Theoritical IV IV C181 IV C182 IV C182
Real IV 0.95xTheoricital Value
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