LIPIDS LAB ACTIVITY

Post Lab Discussion: (Lipids)

LIPIDS
• Biological molecules that are
insoluble in aqueous
solutions and soluble in
organic or nonpolar solvents
are classified as lipids.
• Lipids naturally occur in
most plants, animals, and
microorganisms.
Post Lab Discussion (Lipids)
Post Lab Discussion (Lipids)
Post Lab Discussion (Lipids)
 Post Lab Discussion (Lipids)

A. PHYSICAL
PROPERTIES
Property Saturated Fats Unsaturated Fats

Appearance Typically solid at room temperature Typically liquid at room temperature

Consistency Solid or semisolid Liquid

Varies depending on the specific type of

Color Often white or off-white unsaturated fat. Can range from clear (e.g.,
vegetable oils) to yellow (e.g., olive oil).

Mild to moderate odor, can be nutty or

Odor Often odorless or neutral in odor
plant-based, but generally not strong.
 Post Lab Discussion (Lipids)

B. SOLUBILITY TEST
Solvent Solubility of Lipids The solubility of both saturated and
Water Insoluble unsaturated fatty acids depends on the
Dilute HCl Insoluble
polarity of the solvent, with nonpolar
solvents being the most effective for
Dilute NaOH Insoluble
dissolving them. Unsaturated fatty acids
Chloroform Soluble exhibit slightly higher solubility due to
Cold Alcohol Soluble (Slightly soluble) double bonds, which introduce some
Soluble (nearly at boiling
polarity into the molecules, making
Hot Alcohol them more amenable to dissolution in
pt)

Ether Soluble
nonpolar and moderately polar solvents.
Acetone Soluble
 Post Lab Discussion (Lipids)

c. Formation of translucent spot

Translucent spots form in
oils as they cool because
different parts of the oil
solidify at varying rates.

Some parts solidify quickly,

while others solidify more
slowly.

These variations in
solidification create spots
that appear translucent.
 Post Lab Discussion(Lipids)

Rancid oil is formed when oils and fats undergo a process

c. Reaction of fats called lipid oxidation.
• Oxidation: Oxygen in the air reacts with the double
Red Litmus Blue Litmus bonds in the unsaturated fatty acids present in oils. This
Oil Type Paper Paper reaction leads to the formation of free radicals, which can
initiate a chain reaction of oxidative processes.
• Rancidity: As the oxidation progresses, the oil may
No significant No significant develop a rancid or stale odor and taste, which can be
change (Neutral change (Neutral unpleasant. Rancid oils can also have altered color and
Coconut Oil
to Slightly to Slightly texture.
Alkaline) Alkaline)
The primary change associated with rancidity is related to
the production of organic acids as byproducts of the
oxidative breakdown of lipids. These acids can make the oil
May turn red May turn red more acidic, but the change in pH may not be large enough
Rancid Oil
(Acidic) (Acidic) to be readily noticeable using a standard pH test. The best
way to detect rancidity in oils is through sensory evaluation
(smell and taste) and monitoring for the development of off-
putting flavors and odors.
 ACROLEIN FORMATION
The addition of potassium bisulfate (KHSO4) to
glycerol can result in an odor change due to chemical
Test for Glycerol Odor:
reactions, specifically the formation of esters. Here's
how the test with KHSO4 might affect glycerol:
Result: Typically, glycerol is odorless
or has a very faint, slightly sweet odor. Test for Glycerol Odor in the Presence of KHSO4:

Result: When KHSO4 is added to glycerol, it can

Interpretation: If you do not detect
catalyze the esterification of glycerol with any
any unusual or strong odors, it available acids or alcohol contaminants. This can lead
suggests that the glycerol is pure and to the formation of esters, which often have distinctive
of good quality. Any noticeable off- fruity or sweet odors.
odors, strong smells, or foul odors
Interpretation: The presence of a fruity or sweet odor
could indicate contamination or
in glycerol after adding KHSO4 suggests the
degradation of the glycerol formation of esters through esterification. This result
may indicate the presence of acid or alcohol
contaminants in the glycerol.
 ACROLEIN FORMATION
Esterification reactions can occur when glycerol, which contains hydroxyl (OH) groups,
reacts with acids in the presence of a catalyst like KHSO4. The resulting esters can have
characteristic fruity or sweet odors. Therefore, any change in odor during this test may
indicate the presence of contaminants in the glycerol that have undergone esterification
with glycerol. This reaction can also provide valuable information about the quality or
purity of the glycerol being tested.

Odor: Burnt cooking oil

 TEST FOR UNSATURATION (Halogenation)
Indicate the amount of double bonds present in the Lipid sample.
TT NO. Sample Reagent Hubl’s Solution Result No. of
drops
1 Olive oil 1 ml Iodine in Hg(II)Cl Violet(crystals)/(light orange-brown More
(highly Chloroform/ether solution color solution) of Iodine fades away number of
unsaturated) if fats is unsaturated drops
• Yellow Solution
2 Oleic acid 1 ml Iodine in Hg(II)Cl Violet/brownish color of Iodine 5 drops
( monounsatura Chloroform/ether solution fades away, fats is unsaturated
ted) • Yellowish brown
3 Stearic acid 1 ml Iodine in Hg(II)Cl Violet color of Iodine does not fade 1 drop
Chloroform/ether solution away, fat is saturated
• Reddish brown (No Reaction)
4 Coconut oil 1 ml Iodine in Hg(II)Cl Violet color of Iodine does not fade 1 drop
Chloroform/ether solution away, fat is slightly unsaturated
• Yellow solution
 EMULSIFICATION OF FATS
COMPONENTS OBSERVATIONS/REACTIONS DESCRIBE EMULSION
FORMED
Tube #1: COCONUT OIL When shaken globules were formed Temporary
+ WATER but upon standing for sometime it
forms two layers
Tube #2: COCONUT OIL Smaller globules of coconut oil were Permanent
+ Na2CO3 dispersed in water
+ Water
Tube #3: COCONUT OIL Smaller globules of coconut oil were Permanent
+ ALBUMIN dispersed in water
Solution
 QUESTIONS:
1. Why are fats soluble in organic solvents but not in water?
- Lipids are soluble in non-polar solvent (ether, chloroform, benzene etc) but
insoluble in
water.
- Hydrophobic (Lipids. Fats, oils, and waxes)they won't mix with water.
- Water molecules are polar because they have positive and negative ends.

2. What is emulsification?
- a process where one liquid being dispersed as small spherical droplets in a
second immiscible liquid.
In general, there are two parts of an emulsion.
- The liquid portion of an emulsion in which another liquid is dispersed (O/W, W/O).
3. Enumerate the emulsifying agent used in this experiment.
- Na2CO3, Egg Albumin

4. How do fats and oils affect the surface tension of water?

- Putting oil which has lower surface tension than water reduces surface
tension. The layer of water molecules and layers of oil molecule balance
force between the two interface reducing surface tension at the surface of
water.

5. What is saponification?
- a process involving the hydrolysis of fats on its reaction with
alkali (NaOH or KOH), thereby leading to the formation of salts of fatty
acids (soap) and glycerol.
Oil + inorganic base → alcohol + soap
6. What causes rancidity of fats?
- Rancidity is the process by which fats and oils become degraded,
resulting into off-odor/flavor taste, and texture.
- It is caused by the oxidation of unsaturated fatty acids and can be
accelerated by factors such as exposure to light, heat and air.
7. What is acrolein?
- is the simplest unsaturated aldehyde. A colorless to pale yellow
liquid with strong, pungent odor (smells similar to a burnt cooking oil).

8. What will give positive result to acrolein test? Why?

- A test used to determine the presence of glycerin or fats.

WHY? When a dehydrating agent is heated along with a fat, the molecules of
the glycerol portion will dehydrate and form acrolein.