Characterization of Lipids PDF

7/30/2019 Characterization of Lipids PDF

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CHARACERIZATION OF LIPIDS

SOLUBILITY Insoluble in water

Insoluble in ordinary solvents

Readily dissolve in chloroform, benzene, ether,

boiling alcohol and other organic solvents


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FORMATION OF TRANSLUCENT SPOT Lipids have a characteristic greasy feel

When brought in contact with a substance likepaper, penetrate through it producing atranslucent spot

Fats are non-volatile

In RT, the spot of water can absorb enough heat fromthe air and evaporized

But the spot of grease can never absorb enough heatto evaporized

When the liquid is inside the sheet of paper, itdiffracts lightTRANSLUCENT PHENOMENON


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REACTION OF FATS Fatty acids are carboxylic acids and are therefore

weak acids

For fatty acids, the value of pKa is around 4.5.Therefore, generally speaking, fatty acids areneutral below pH 4.5 and charged above pH 4.5

Fats containing high unsaturated fatty acids areneutral in reaction, but when exposed to airbecome acidic due to hydrolysis which resultsfrom the liberation of volatile fatty acids


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ACROLEIN FORMATION

- 2H2O

Glycerol Acrolein (acrid odor)

dehydrating agent

(potassium bisulfate)


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EMULSIFICATION OF FATS


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EMULSION Is a mixture of two or more materials that are

ordinarily immiscible

Droplets of the dispersed component rapidlycoalesce to form a separate layer

Emulsifying agent must be present to stabilize

the emulsion

Lecithin in the egg will serve as emulsifier


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SAPONIFICATION OF LARD Alcoholic Potash

KOH dissolved in ethanol

To neutralized fatty acids in the lard

A metallic salt of fatty acid is formed

Hydrophobic tails extend into the greasy droplets

whereas the polar heads of the soap molecules

face toward the water


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SAPONIFICATION OF LARD Sodium Carbonate to produce hard soap

Palmitin Palmitate + Glycerol

Soap


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SEPARATION OF CHOLESTEROL ANDTRIGLYCERIDES

Precipitate = cholesterol digitonide after

digitonin precipitation Supernatant = triglycerides

PRECIPITATE tested for Salkowski Test andLiebermann-Burchard Test

Test for cholesterol


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SALKOWSKI TEST The presence of a double bond in one cholesterol

rings is responsible for its ability to form color

products in the presence of concentratedinorganic acids

Sulfuric acid

Results in dehydration of cholesterol molecule with a

formation of a red bicholestadien disulphonate

Bluish color between the 1st layer (chloroform)

and 2nd layer (H2SO4)


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LIEBERMAN-BURCHARD TEST Deep green color (+)

due to the hydroxyl group (-OH) of cholesterolreacting with the reagents (acetic anhydride and

concentrated sulfuric acid) and increasing the

conjugation of the un-saturation in the adjacent

fused ring


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TRANSITIONAL PAGE

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Characterization of Lipids PDF