LipidsBayan, Charmaine Rose Jean L.

Himor, Jomarie Mhel P.Marquez, Ella Mae H.

Objectives:

• To distinguish the different properties of lipids through the different test performed and different reagents used.

Data and ResultsSAMPLE SOLVENT USED RESULT EXPLANATION

Cottonseed Oil Distilled Water

Ethyl Alcohol

Insoluble; formation of

globules

There are more hydrocarbons in a

lipid molecule which are largely hydrophobic than their polar side,

thus, making them insoluble especially

in polar solvent

EtherSoluble; clear; one

phaseThey are non-polar solvents, thus the lipid molecules are

soluble in them because of the

presence of Vander waals forces.

ChloroformSoluble;

translucent; one phase

Benzene Soluble; one phase

Data and ResultsMIXTURE RESULT EXPLANATION

Cottonseed oil-ethyl alcohol

Cottonseed oil-ether

Name for Test Sample Reagent needed

Results Explanation

Test for unsaturation Oleic Acid Bromine in

CCl4

3 drops needed to change

There is a lesser number

of double bonds in the oleic

acid, thus the color changed

right away

Palmitic Acid CholoroformHanus Iodine

Light pink to light yellow (30

minutes)It took a while for it to change since there are

more unsaturated

bonds in these group of lipids.

 

Oleic Acid ChloroformHanus Iodine

Light pink to light yellow (30

minutes)

Cottonseeed Oil

ChloroformHanus Iodine

Light pink to light yellow (30

minutes)

Name of Test Sample Reagent Added Result Explanation

a. Acrolein Test Glycerol KHSO4 No odor

There is no odor because fats are

odorless

Cottonseed KHSO4 No odorThere is no fat present in the

cottonseed oil, thus, it smelled like

chicharon/used oil

b. Rancidity Test Fresh

Coconut OilPhenolphtalein Colorless

There is no reaction

Methyl Orange Red

OrangeThe solution became

acidic

pH paperBlue color of

the litmus paper

remained the same

The fatty acids are still present in the fresh coconut oil. Thus changing the

blue litmus paper to red

Name of Test Sample Reagent Used Reaction Explanationb. Rancidity Test

Rancid Coconut Oil

Phenolphthalein No change, same color

with the rancid oil

The fatty acids are still present in the glycerol. Thus changing

the litmus paper into red.

Methyl Orange Red

Orange

pH paper Blue color of the litmus

paper remains the

same

Name of Test Sample Reagent Used Reaction Explanation

E. Saponification

Coconut Oil 10% Potassium Hydroxide(KOH)

Formation of gelatinous mass

Name of Test Sample Reagent Used Reaction ExplanationF. Properties of

Salting OutSoap Solution NaCl Crystallized

formed

White substance

Smells like coconut

Formation of Fatty Acids

Soap Solution 10% HCl Cloudy solution

Formation of bubbles on the walls of the test

tubeInsoluble Soaps Soap Solution 5% CaCl2 White

precipitate formed

Cloudy Solution

Name of Test Sample Reagent used Reaction ExplanationInsoluble Soaps Soap solution 5% MgCl2 White

precipitate formed

Cloudy Solution

Detergent 5% CaCl2 White precipitate

formed

Cloudy Solution

Name of Test Sample Reagent used Reaction Explanationa. Liebermann-Buchard Test

Cholesterol CHCl3 acetic anhydride;

concentrated sulfuric acid

From white cloudy solution

to dark

Blue to blue green in color

This test determines the

presence of cholesterol and

it indicated a positive test

when the color changed

Name of Test Sample Reagent used Reaction ExplanationE. Emulsifying

Action of Lecitihin

2% Albumin Cholesterol

Cholesterol lecithin

2 layers formed; soluble

in albumin

There was no layer formed

and the cholesterol

“mixed” with albumin

2 layers were formed since 2% albumin

and cholesterol do not mix.

Lecithin

Question and Answer:

1.Why are fatty acids insoluble in water?• Fatty acids are insoluble in water since

there are more hydrocarbons which are more hydrophobic than the carboxyl group which is soluble in water. The longer the chain of the fatty acid becomes, the more insoluble it gets.

2.Explain why the cis-form is more predominant configuration of unsaturated fatty acids?

• Cis-form configuration is more predominant in unsaturated fatty acids since most of the fatty acids are in liquid form, and most of these liquid form unsaturated fatty acids has this configuration.

3.Why is the acrolein test the general test for fats?

• Acrolein test is used because it is the product/result when a substance with a fat in it is reacted with the reagent, potassium bisulfate and heat. Thus, if an acrolein is produced from the reaction, fats are present in the substance.

4.What type of rancidity occurs in vegetable shortenings and how can it be prevented?

• The type of rancidity that occurs in vegetable shortenings is the oxidation rancidity In this ‘oxidation rancidity’, the oxygen molecules interact with molecules of the oil which causes damage or changes to the substance.

• The easiest way to prevent this from happening is to store these vegetable shortenings in a dark, cool place where it is less exposed to oxygen.

5.Explain the cleansing action of detergents• The cleansing action of the detergent is

caused by its molecular structure.the hydrophobic part of the molecule is attracted to other hydrophobic substances such as oils, and the like, and the hydrophilic part attaches itself to the water , and thus, when it is rinsed away with water the hydrophobic part that is attached to the water

6. Write the structure of the parent compound of cholesterol.

7.Explain the cooperative solvent effect of lecithin and albumin.

• Lecithin and albumin are good emulsifiers because they both have a non-polar and a polar portion which helps reduce the immiscibility of two substances. When they work hand-in-hand, they are able to hold polar substances through their hydrophilic molecules thus making the immiscibility of two substances possible.

Conclusion:• The different test performed in the lipids

determined some of its properties

Solubility test determined that lipids are largely non-polar(since they only dissolved or mixed with non-polar substances e.g. ether, benzene, chloroform) thus they tend dissolve in non-polar substances also.

• The test for unsaturation determined the varying number of double bonds that each fatty acid or lipid contain.

• In the acrolein test, it was determined that not all oils contain fats, since the cotton seed oil did not give off a positive result for the acrolein test.

• In the rancidity test, the test showed that it is acidic, thus there was no oxidation that occurred (especially in the rancid coconut oil.)

• In the liebermann-burchard test the cholesterol turned into blue-green which indicated the presence of cholesterol.

• Last but not the least with the presence of lipids (lecithin)which act as emulsifiers, two immiscible substances are able to mix together due to its hydrophilic and hydrophobic parts that aid in the mixing of the substances