For a very long time now, palm oil remains to be the most popularly used vegetable oil all over the world. You might think, not everyone uses palm oil for their everyday cooking. However, if you would look at the labels of most edible as well as non-edible consumer products also, you would see the name “palm oil” there. In different forms, palm oil is added to various products like chocolate bars, coffee creamer, margarine, toothpaste, and even, shampoo. Wondering how palm oil and its derivatives reach each of those things? You might find this article helpful. Read on! (Hyperlink the why is palm oil so popular)
Let’s take a look at how palm oil is harvested, where it comes from, and how it ends up in the products we consume.
Table of Contents
What is Palm Oil
Obtained from the fruit of the oil palm tree, palm oil is an extremely popular edible oil. Palm oil is a vegetable oil like coconut oil. It holds both saturated and unsaturated fats, and it is a rich source of polyunsaturated fatty acids and monounsaturated fatty acids, palmitic acid, stearic acid, and myristic acid in very small amounts. Here are the values of these components:
- Saturated fatty acids- 50%
- Unsaturated fats in the form of
- Polyunsaturated fatty acids- 40%
- Monounsaturated fatty acids- 10%
- Palmitic acid- 44%
- Stearic acid- 5%
- Myristic acid- traces
Palm Oil Cultivation
The procedure starts with palm kernel seeds as palm tree cultivators select the best quality seeds to start the germination. Seeds like Topaz 1, Topaz 2, Topaz 3 and Topaz 4 are specially developed to produce higher yields even when the cultivation environment is just average.
The next step of a good plantation is selecting good quality seedlings of the right kind of right palm tree. The recommended variety of oil palm trees grown globally is called Tenera. This variety is a crossbreed amidst dense skinned, mother palm called the ‘Dura’ and ‘Pisifera’ which is a pollen plant and it has no shell. The figure below shows how the three fruits look like:
The Tenera variety is an oil-rich palm tree variant that has a light shell. The fruit of this palm tree has average to above-average pulp content. The pulp of this tree has high amounts of oil. On average, palm seedlings are grown in the nursery for 6 months.
Once the palm seedling is planted in the palm cultivation, the trees grow and reaches maturity after approximately 3 years. In the third year, the harvesting begins and continues till the tree reaches the age of 18 years. Between the age of 7 to 18 years, oil palm trees yield their best crops. After the 18th year, the yield begins to diminish. The trees can be harvested every 10 days, when a suitable number of fruits start looking detached from the palm fruit bunch. This visible detachment is known to be a sign of maturity and ensures a decent quantity and quality harvest. The reaping happens in the form of bunches only. Any individual palm fruits that fall on the ground are collected in bunches and included in the extraction pile to minimize wastage.
The picture shows- a) Oil palm tree with ready bunches. (b) A bunch with detaching fruits. (c) Anatomy of a palm fruit
Once all pollinated, the palm fruit looks like a medium-sized plum and its color ranges from bright deep violet to a flaming orange and red. Each palm fruit is home to almost 50% oil, where both the flesh and the seed contain and produce oil. The weight of an individual palm fruit ranges from 6 grams to 20 grams. The exterior covering of palm fruit is called the exocarp, the pulp that contains the oil is called the mesocarp, the shell that covers the nut is called the endocarp, and the innermost part is the kernel. The mesocarp holds around 70 to 80% of oil. The oil harvested from the mesocarp is called the crude palm oil.
The crude palm oil is red and it largely contains mono, diacylglycerols, and triacylglycerols. Additional elements in the crude palm oil are FFA (free fatty acids), grime, moisture, and secondary segments of the other material. This is mostly non-oil fatty matter referred to collectively as unsaponifiable material. These components in Crude palm oil are percentages in the following percentages:
- Triacylglycerols- 90.35%
- FFA- 3.5%
- Diacylglycerols- 4.7%
- Monoacylglycerols- 0.2%
- Moisture and impurities- 0.25%
- Unsaponifiable material- 1%.
The fundamental method of palm oil harvesting goes like this: sterilization → fruit and nut detachment → extraction of palm oil → refining → separation. In palm oil harvesting, there are many steps involved in each of the above-mentioned processes. Here is how a palm oil production line works.
Collection of Bunches
When the palm fruit is mature, the bunches are harvested from palm trees by skilled labor with the help of a long sickle or machete.
After harvesting, the palm fruit bunches are brought to the processing facility where they are weighed and stored under controlled conditions. Proper storage helps in controlling the action of enzymes and contaminants in the food.
Sterilization
Collected palm fruit bunches go through a steaming or cooking process under hot wet-heat handling. Performed either with hot water or with pressurized sterilization, this process helps in killing oil-splitting proteins and stops autoxidation of the harvested bunches. As the fruit clusters and bunches are treated as whole, the sterilization process also aids in easy detachment of stems in the procedures to follow. The heat in the sterilizer crystallizes proteins which help in the easy flow of the oil later. The figure below shows how the sterilizer looks.
Threshing
This process is dedicated to spreading the palm fruit taken from branches and coverings. The equipment used for this process is a fixed or a revolving drum that has encircling beater bars attached to it. This machine detaches the fruit from the stem. Centrifugal separation circumrotation or a similar powerful vibration is then used for the separation. A properly done threshing considerably increases the productivity of the palm oil harvesting process and helps in cutting down the labor costs. The stems separated during the threshing process are either burnt as cooking fuel or processed into ash, and used as a potassium-rich fertilizer.
Digestion
Quite like its name, digestion is the process that helps in breaking the nut down. The digestion process breaks the oil-bearing cells with the help of steam. This step is performed in a steam-operated vessel called a digester. A basic digester looks like this:
This cylindrical vessel has an inner rotating handle fitted with multiple beaters like arms. The stirring action of these arms pound the fruit. This pounding happens at a high temperature and helps in getting rid of the exocarp. Digestion helps in exposing the productive part of the fruit, reduces the viscosity and gets the matter ready for the next step called the pressing.
Pressing
In the modern palm oil industry, screw pressing is the most popular method of palm oil extraction. At this step, a screw press is used for the extraction of palm oil from the combination of ingested and beaten palm flesh. Palm pulp right now is a compound of oil, fiber, kernels, and lots of water. There are 2 kinds of systems that are used for pressing palm oil.
- Batch Pressing System
This mechanism loads steamed palm flesh and yields the freshly produced crude palm oil directly to the clarification machine. The upright digester has a perforated base plate that pounds the palm fruit matter batch-wise and later washes the crude palm oil and additional non-oil masses out of the crushed palm fruit pulp with boiling water. The batch type screw press system pounds a batch of churned fruit at the start while applying force on crushed palm flesh in another segment to extract the palm oil.
- Continuous Pressing system
The continuous press system is equipped with a bar-shaped perforated enclosed cell that has a tight-fitting spiral-like screw running within itself. The kernels are continuously transferred through the assembly and led to a hole enclosed with a tube. This creates the strength that is required to discharge the oil through the apertures in the machine.
Whatever pressing system is used, the end result is the palm oil being extracted and collected in tanks, where it goes through a clarification process.
Clarification
After the crude oil has been pushed out of the fruit, it would obviously still have many impurities. These impurities are metal particles, dirt, cell debris, fibrous residue, moisture, and ‘not-fatty solids’. Remember the unsaponifiable material? Yeah, we are still going to have to deal with it. Get ready!
The chief purpose of this step is to separate the oil and the above-mentioned entrained contaminants. The presence of the non-fatty solids makes this mixture quite viscose.
To start the clarification process, first hot water is added to this raw mix to make it thinner. This dilution renders a sedimented dust block and makes the large masses sink to the bottom of the vessel. While the heavier impurities go down, the lighter droplets of oil come up through the liquid mixture. At this time, the mixture is heated again to split the emulsion. This also aids in the separation of the resin. Let’s see how does the clarification machine looks:
This thin mixture of oil and water passes through a vibrating screen to remove the fibrous material. The sifted blend is then cooked in a large tank again for a couple of hours and then left to settle with the course of gravity. As oil is lighter than water, the palm oil rises to the top and forms a layer on top. After this, this cleaner version of the oil is decanted into a reception tank. This oil looks clear and cloudless, but, it still has some particles of dirt and vapors.
The presence of water in the oil increases the chances of fatty acids and the subsequent deterioration of the quality of purified oil. Hence, the water content in the oil must be diminished to 0.20%. So, the decanted oil is reheated in a large pot. Then, the dried oil is carefully skimmed off the ingrained dust particles. The heating action lets the water evaporate, and by the end of this process, crude palm oil is obtained.
Crude palm oil also called the Red palm oil
The crude oil obtained at this stage is also known as the red palm oil because the crude palm oil is red in color. It has a strong taste and smell. Some amounts of red palm oil are packed and sold in the markets. However, most of it is processed further to get refined palm oil. Refined palm oil is a neutral oil that looks yellowish golden and has no smell.
Obtaining refined oil from crude oil has to do with removing the consequences of oxidation and hydrolysis, appearance, and taste.
This is where you do fractionation, and the process is:
- Degumming- To get rid of the leftover impurities from the crude palm oil, it is put under controlled heat and phosphoric acid is mixed into it. This helps is segregating the impurities, which are later removed during the bleaching and filtration stage.
- Bleaching- As the name suggests, this process helps in neutralizing the color of palm oil. Acid- activated earth is put into the oil mixture. This absorbs the red color pigment from the oil.
- Filtration- At this stage, the clay that was put in the oil is filtered out, and along with the activated earth, the leftover impurities are also filtered out of the new palm oil.
- Deodorization- During this process, the hot oil is treated with vacuum-steam distillation. Here, the fatty acids and the odor producing agents are removed from the oil. A totally bland and odor-free oil is obtained at this point. It is also called the RBD palm oil, which is readily available in the markets.
- Fractionation- Where some oil is sold in the form of RBDPO, rest goes through fractionation and where hot oil is slowly cooled down and extracted at various crystallization stages. The liquid fraction is called the olein, which is another product sold widely as cooking oil, while the solid fraction is called stearin, which is sold as a subtype dilute form of baking fat and margarine.
- Packaging- Different products that have been harvested are packages into bottles, containers, and jars.
Conclusion
The oil palm is a truly versatile crop that has lots to offer. From your cooking oil to your baking soda, palm fruit is the answer. The fruit of this tree is full of oil, and so, is its kernel. The oil harvesting process starts from the reception of fresh oil palm bunches, after that the bunches are sterilized and stripped. Then comes the digestion and pressing out of the crude oil which is then clarified. Be it the crude oil harvested at this stage or the various palm oil products that are obtained at different stages of refining, all are well appreciated in various industries. Palm oil products are used for domestic cooking, commercial cooking, packaged food industry, oleochemical industry, animal feed industry and much more.
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