Chapter IX (the last chapter)

OILS Mineral oils Organic oils ( lipids) Compound lipids HETEROLIPIDS Simple lipid HOMOLIPIDS Derived lipids Steroids Phospholipids Testosterone, estrogen, Cholesterol vitamins Triglicerides Waxes Esential oils

Oils and Fats (Analaysis) 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

Fats and oils Edible Non edible Analysis

Chemical analysis of oils quantitative and qualitative

Analytical Methods Saponification Value (Polanski value or the Reichert-Meissl-Wollny value) Iodine Value Acid Value Thiocyanogen value or thiocyanogen number Active Oxygen Method (AOM) Peroxide value Ultraviolet Spectroscopy FT-IR spectroscopic method

saponification Show the reaction of saponification of the next esters: Trimyristin (Myristic acid C14:0) Triolein (Oleic acid 18:1cis-9)

1. Saponification Value 3 + 3 K+OH - O - R C H2C H2C OH O HC + HC KO - triacylglycerol HC H2C OH glycerol HC H2C C O - R KO - + 3 K+OH - 3 + Potassium salt Similarly; RCOOH + KOH RCOO-K+ + Glycerol MG + KOH RCOOK + Glycerol DG + 2KOH 2RCOOK + Glycerol

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 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

Saponification Value What is the MWTG ? O O O - R1 - R1 C - R C H2C C

Saponification Value Determination Saponification # --mgs of KOH required to saponify 1 g of fat. 1. 5 g of fat 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.

Saponification Value Milk Fat 210-233 Coconut Oil 250-264 Cotton Seed Oil 189-198 Soybean Oil 189-195   Fat SV Lard 190-202

iodination Linoleic acid 18:2 cis,cis-9,12

2. Iodine Number Halogenation (iodination)   unsaturated fatty acids

Determination of Iodine Number Excess unreacted ICl 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)

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 freshneess oils.

Theoretical Iodine Value Monoene + I2 Saturated Diene + 2*I2 Saturated Triene +3* I2 Saturated

Theoretical Iodine Value 1 mol C18:3 3 mol I2 (3x254 g) 1 g C18:3 X (g) I2

Theoretical Iodine Value 1 mol C18:1 1 mol I2 (254 g) 15 g C18:1 X (g) I2 1 mol C18:2 2 mol I2 (2x254 g) 40 g C18:2 X (g) I2 Assumption: Oil =TG FA xi C16:0 5 C18:0 15 C18:1 15 C18:2 40 C18:3 1 C20:0 3

Write the structural formula and give the name of this fatty acid: C18:3, Omega-3 Explain where belongs to the MUFA or PUFA class of fatty acids.

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

4.Thiocyanogen value or thiocyanogen number a measure of unsaturation (as of an oil or fat) expressed usually as the number of grams or percentage of iodine equivalent to the thiocyanogen absorbed by 100 grams of the substance. Serving as a supplement to the iodine number because thiocyanogen adds to double bonds to a different extent from the usual reagents for determining iodine number … is thus different from the ordinary value in that it differentiates between oleic C18:1cis-9, linoleic C18:2 cis,cis-9,12., and linolenic groups C18:3 cis-6,9,12 Thiocyanogen, (SCN)2, is a pseudohalogen derived from the pseudohalidethiocyanate, [SCN]−. This hexatomic compound exhibits C2 point group symmetry and has the connectivity NCS-SCN.  The oxidation ability is greater than bromine. 

Lipid Oxidation

Measurement of lipid oxidation Active Oxygen Method (AOM) Iodine value or Peroxide Value is measured over time as Oxygen is bubbled through an oil sample This method is also used to evaluate antioxidants

5. CHOLESTEROL DETERMINATION total cholesterol levels should be: 5mmol/L or less for healthy adults 4mmol/L or less for those at high risk Enzymatic Determination: Cholesterol Oxidase In enzymatic analysis (which is widely used in medical laboratories) the color reaction is preceded by a reaction catalyzed by an enzyme.

Cholesterol by GLC 1. Prepare cholesterol butyrate. 2. Analyze by GLC. time in GC - 15 min. sensitivity - 10-7 g.

7. Peroxide Value Hydrolytic Rancidity Definition   7. Peroxide Value Definition The peroxide value (PV) is a figure used for determining the peroxide oxygen (especially hydroperoxides). It is expressed in milliequivalents of active oxygen per 1 kg of fat. The peroxide value is used for identifying the onset of oxidative change in fats and oils, during which the oxygen (O2) molecule penetrates the fat molecule in the form of a peroxide group (H2O2).   The peroxide value is a quality criterion for explain the freshness of edible oils. The lower the figure, the fresher the oil. Crude pressed oils have a PV of 5-20, refined oils 0-1.

The peroxide value is defined as the amount of peroxide oxygen per 1 kilogram of fat or oil.

8. Analyzing Olive Oil Purity with Ultraviolet Spectroscopy using the UV-1800 Spectrophotometer from Shimadzu

Methyl bromide Methyl Iodide Chromophore Example Excitation λmax, nm ε Solvent C=C Ethene π  __>   π* 171 15,000 hexane C≡C 1-Hexyne 180 10,000 C=O Ethanal n  __>  π* π  __>  π* 290 180 15 10,000 hexane hexane N=O Nitromethane 275 200 17 5,000 ethanol ethanol C-X   X=Br       X=I Methyl bromide Methyl Iodide n  __>  σ* n  __>  σ* 205 255 200 360 Measured K Values Olive Oil Sample Type K232 K264 K268 K272 ΔK Extra Virgin Sample 1 2.379 0.179 0.173 0.165 0.001 Extra Virgin Sample 2 1.911 0.207 0.214 0.209 0.006 Extra Virgin Sample 3 2.085 0.130 0.135 0.134 0.003 Olive Oil Sample 4 2.373 0.686 0.759 0.663 0.085 Olive Oil Sample 5 2.180 0.701 0.772 0.675 0.084 Criteria K Values Extra Virgin Olive Oil ≤ 2.50   ≤ 0.22 ≤ 0.01 Olive Oil - ≤ 0.90 ≤ 0.15

9. Analysis of Degraded Machine Oil by FTIR