5.5 Palm Oil
Palm oil is an important vegetable oil derived from the oil palm fruit. Explore the structure of the fruit, the industrial extraction process, the chemistry of palm oil, soap production and the sustainable management of the oil palm industry.
Learning Objectives
- Describe the structure of the oil palm fruit and the parts that contain oil.
- Explain the sequence in the industrial extraction process of palm oil.
- State the chemical properties, nutritional content, and uses of palm oil.
- Describe soap production through saponification and the cleansing action of soap.
- Explain the sustainable management and zero waste concept practised in the oil palm industry.
Industrial Palm Oil Extraction and Soap Cleansing Action
Follow the journey from oil palm fruit to pure oils, and see how a soap molecule removes grease.
Short Explanation
What is palm oil?
Palm oil is a vegetable oil obtained from the pulp (mesocarp) of the oil palm fruit, while palm kernel oil is obtained from the kernel.
The oil palm fruit consists of three parts: the pulp, the shell and the kernel. The pulp contains the most palm oil, the kernel contains the best quality palm kernel oil, and the shell does not contain oil.
Chemical composition
Palm oil consists of glycerol and various fatty acids. It contains saturated fatty acids such as palmitic acid and stearic acid, and unsaturated fatty acids such as oleic acid and linoleic acid. Palm oil has an equal ratio (1.0) of unsaturated fats to saturated fats, making it a balanced oil.
Chemical properties
Palm oil undergoes oxidation, hydrolysis, and esterification. During esterification, fatty acid molecules from palm oil react with alcohol to produce methyl ester, which serves as palm oil biodiesel.
Nutritional content and uses
Palm oil is rich in vitamin E and vitamin A, and contains antioxidants such as carotene and vitamin E. It is used in cooking oil, margarine, vegetable oil and chocolate, as well as in soap, cosmetics, medicine, plastic surgery and prosthetics.
Structure of the Oil Palm Fruit
Each part of the fruit has a different role in oil production.
| Part | Description | Oil content |
|---|---|---|
| Pulp (mesocarp) | The fleshy middle layer of the fruit. | Contains the most palm oil (PO). |
| Shell (endocarp) | The hard inner layer surrounding the kernel. | Does not contain oil. |
| Kernel | The seed inside the fruit. | Contains the best quality palm kernel oil (PKO). |
Activity 5.9: Observation and Extraction Aspect
Boiling fruits softens the pulp and destroys microorganisms and enzymes. Squeezing the boiled pulp yields palm oil, which is reddish-orange due to carotenes. Extracting the kernel yields palm kernel oil, which is clear or light yellow.
Industrial Extraction Process of Palm Oil
The sequence from harvested bunches to pure palm oil and palm kernel oil.
1. Bunch of oil palm fruits
Harvesting bunches from the plantation.
2. Sterilisation
The whole bunch is sterilised with steam at high pressure and temperature. Heat kills microorganisms that spoil the fruits, and steam softens the pulp and facilitates fruit detachment from bunches.
3. Threshing
Oil palm fruits are detached from their bunches using a threshing machine.
4. Digestion
Fruits are reheated at high temperature and pounded by rotating beater arms to separate the pulp from the shell. The pulp and shell are then processed separately.
5. Extraction
The pulp is squeezed using a hydraulic or spindle press to extract palm oil. The shell containing the kernel is steamed at high pressure, the kernel is separated and dried, and palm kernel oil is extracted using a hydraulic or spindle press.
6. Filtration
Pulp fibres are separated from palm oil through filtration. Kernel debris and particles are separated from palm kernel oil through filtration.
7. Purification
Steam is flowed through palm oil to remove odour and eliminate acid causing sourness. Palm oil flows through activated carbon to be decolourised.
8. Final Products
Pure palm oil and pure palm kernel oil.
Soap Production and Cleansing Action
Saponification turns palm oil into soap, and the soap molecule removes grease.
Saponification
Saponification is the reaction between palm oil and a concentrated alkali to produce soap and glycerol.
Word equation: \[ \text{Oil} + \text{Alkali} \rightarrow \text{Fatty acid salt (soap)} + \text{Glycerol} \]
The alkali used is concentrated sodium hydroxide, \(\text{NaOH}\), or concentrated potassium hydroxide, \(\text{KOH}\).
Experiment 5.1 Steps
1. Boil palm oil with concentrated \(\text{NaOH}\) solution for 5 minutes.
2. Add distilled water and sodium chloride (\(\text{NaCl}\)) to precipitate the soap.
3. Boil for another 5 minutes and filter. The residue on the filter paper is soap.
4. Soap is slippery when touched, forms lather with water, and turns red litmus paper blue.
Hydrophilic head
The ionic group of the soap molecule. It dissolves in water and is repelled by grease.
Hydrophobic tail
The hydrocarbon chain of the soap molecule. It dissolves in oil and grease, and is insoluble in water.
Cleansing action of soap
1. Soap reduces the surface tension of water, completely wetting the cloth.
2. The hydrophobic tail dissolves in the greasy dirt, while the hydrophilic head dissolves in water.
3. Scrubbing dislodges the greasy dirt from the cloth into small suspended droplets.
4. Soap bubbles trap greasy droplets; rinsing washes them away, cleaning the cloth.
Sustainable Management and Zero Waste Concept
The oil palm industry converts all by-products into useful resources.
| Biomass waste | Useful application |
|---|---|
| Fronds | Made into fertilisers. |
| Tree trunks | Wood replacement and furniture. |
| Empty fruit bunches | Turned into compost. |
| Shells | Burnt as fuel in boilers to produce steam and boil water. |
| Pulp fibre | Made into carpets and textiles. |
| POME | Turned into biogas and fertilisers. |
Other sustainable practices
Replanting is carried out to optimise agricultural land without deforestation. Palm oil mill effluent (POME) is treated and converted into organic fertilisers and biogas. Oil palm trees absorb carbon dioxide and release oxygen through photosynthesis.
Try to Answer First
Answer in your mind, then press “Check Answer”.
What are the two products formed during the saponification of palm oil with concentrated sodium hydroxide?
Why are oil palm fruit bunches sterilised using steam at high pressure and temperature during industrial extraction?
Which part of a soap molecule dissolves in greasy dirt during the cleansing process?
Common Mistakes
- Confusing the oil extracted from pulp with that from the kernel. Palm oil is from the pulp (mesocarp); palm kernel oil is from the kernel.
- Forgetting that the shell (endocarp) does not contain oil.
- Mixing up the functions of the hydrophilic head and hydrophobic tail of a soap molecule.
- Confusing hydrolysis (reaction with water) with esterification (reaction with alcohol).
- Assuming sodium chloride is added in soap making to react with the oil. It is added to precipitate and separate the soap from the mixture.
Concept Misunderstandings
Palm oil contains only saturated fats and is bad for health.
Palm oil has a balanced composition with an equal ratio (1.0) of saturated fats and unsaturated fats, alongside beneficial antioxidants like vitamin E and carotene.
The cleansing action of soap is purely physical scrubbing.
Soap actively reduces the surface tension of water, and its dual-polarity molecules chemically bridge water and grease to detach the grease droplets.
Summary
- Palm oil is extracted from the pulp (mesocarp), whereas palm kernel oil comes from the kernel.
- Extraction involves sterilisation, threshing, digestion, pressing, filtration, and purification.
- Soap is manufactured through saponification, where palm oil reacts with concentrated alkali to produce soap and glycerol.
- A soap molecule comprises a hydrophilic head and a hydrophobic tail that emulsify and rinse away grease.
- The industry implements zero-waste practices to utilise all biomass sustainably.
Short Activity
A. Objective Quiz
1 Which part of the oil palm fruit contains the highest quantity of palm oil?
2 What is the main function of adding sodium chloride during the laboratory production of soap?
B. Fill in the Blanks
3 In the production of biodiesel, palm oil fatty acids react with alcohol in a reaction called .
4 The part of the soap molecule that dissolves in water is the head.
C. Drag and Drop: Match the Biomass Waste to Its Application
Drag each biomass waste to its correct application under the zero waste concept. On a phone, tap an answer first, then tap a matching box. Tap the Answer Choices area to return a selected item.
C. Match the Biomass Waste to Its Application
Write the correct biomass waste next to each application.
| Useful Application | Biomass Waste |
|---|---|
| 1. Burnt as boiler fuel to boil water | |
| 2. Turned into compost | |
| 3. Made into carpets and textiles | |
| 4. Converted into biogas and organic fertilisers |
Answer choices: Shells • Empty fruit bunches • Pulp fibre • POME
