How is Palm oil refined

Oil palm trees are truly versatile as they have so much to offer, be it red palm oil, or refined palm oil, or palm kernel oil, or palm olein, double stearin, palm kernel expeller, and so much more, the list could go on for a while.

Starting from harvesting the oil palm fruit to being packaged as edible refined palm oil, there are many steps involved. After obtaining the crude palm oil with a basic extraction system, many more steps are followed to obtain the yellowish- golden palm oil that is sold at the supermarkets. Before we dive into this process, let’s learn more about palm oil.

Palm oil is a fat secured from the corpulent reddish-orange pulp called the mesocarp of the palm fruit. Palm tree fruit is a rich source of oil and each mesocarp contains 70-75% oil. In its non-processed form, palm oil is rich in carotenoids, this is why it is mostly orange or red. Upon being fractionated, palm oil yields liquid oil called the olein and solid fraction called the stearin. Oil palm is a rich source of nutrients like beta-carotene and Vitamin E. If you would like to know more about the process, click here. (Link to article on how is plam oil harvested)

As far as the extraction of crude oil is concerned, it is usually processed by a natural and rather simple physical refining process. This crude oil is red and has high contents of the nutrients like carotenoids and antioxidants like tocopherols. After all the impurities are clarified from the crude palm oil, it becomes red palm oil which is known to be extremely healthy. However, this form of palm oil has a peculiar smell and an innate taste. Though in West African cooking, red palm oil is still used and appreciated, the Western markets feel differently. Thus, palm oil is refined to make it more neutral in appearance, smell, and taste.

How does refining happen? Before we understand refined palm oil in detail, let us look at how crude palm oil is obtained. The extraction process of palm oil includes the following steps:

1. Harvesting- Once the oil palm fruit is ripe, the clusters are harvested by skilled labor with the help of a sickle or machete. On average, a bunch is close to 25 kilos. After harvesting the bunches are transported to the oil mill.

2. Sterilization- With the sterilization method, the quality and viability of the palm fruit can be preserved. This process restrains lipase action within the fruits. This controls the flow of free fatty acids and prevents bunches. With the steam treatment performed during this step, the fruits soften and facilitate the stripping of the fruit for the procedures to follow. 

3. Threshing- Like all other crops, the idea of threshing the palm fruit is to separate the outer shell from the oily pulp. 

4. Digestion- Following the separation, the fruit proceeds into the digester, which is a steam-heated vessel that is equipped with rotating shafts connecting to stirring arms. Inside the digester, the fruits are treated with heat so that the pericarp of the fruit loosens. Through the digestion process, the fruits keep rotating continuously causing the kernels to separate from the pulp effectively. 

5. Pressing- It is during this procedure the material obtained is pressed with the help of a screw press, and crude palm oil is extracted. While the pressing goes on, two products are derived- crude palm oil with liquid and solid impurities, which is explored later, and the press cake that is a compound of the palm kernel and fiber.

6. Clarification- Now, the obtained oil needs to be cleaned with different techniques like screen vibration, separation, and cooling & drying. At every step, the oil develops into cleaner and more usable sub-oil.

After drying and cooling, the crude palm oil is packaged either for selling into the markets or for refining. Refining palm oil from crude palm oil is a long procedure in itself. The crude palm oil goes through many different steps of purification before it goes into the market for consumer and industrial use. Let us see how does it happen. Here is a flow chart on the steps of refining:

Quality Check

A quality check determines whether the new palm oil is fit for the things it is later meant to be added to. During the quality check, the crude palm oil is inspected for- 

• Free Fatty Acids (FFA) – Finding an inappropriately large number of free fatty acids in crude palm oil shows that the quality of the palm oil is inferior because of the actions of microbes and enzymes in the palm fruit. It could also mean that crude oil was stored under poor conditions. In case the FFA is high, it is first separated with the help of methods like chemical esterification, molecular distillation, and nanofiltration before it is approved for refining.
• Moisture and Impurities- Crude palm oil is tested for the presence of moisture with the help of a gravimetric system. This method of air oven drying assesses the volume of water present in the oil. The level of impurities in the crude oil is checked too. Depending upon the results, either the oil goes for refining or it goes through the clarification process again.
• Deterioration and Bleachability Index (DOBI) – It is a scientific system applied to determine the quality of crude palm oil. This scale designates the degree of oxidation of the crude oil to be processed. Higher values on DOBI symbolize that the fruit is fresh, mature, and free from contamination. As bleaching is important to bring the palm oil to a neutral color, testing the bleachability of the sample is important as it determines, how much bleaching agent needs to be used. Here is the DOBI values chart:

Following are a few processes used to refine the modern palm oil using advanced machines:

Degumming

Degumming of oils mostly includes the processing of crude oils with agents like water, a salt suspension, or diluted acids. In the case of crude palm, oil degumming is performed with phosphoric acid to get rid of impurities like moisture, phospholipids, and various kinds of waxes. In this process, the crude palm oil is cooked under vacuum and phosphoric acid for the separation of the resins. 

Bleaching

After the degumming process is done, while the acid is mixed in the oil, within a short while, approximately 1 or 2% acid-stimulated bleaching clay is combined with the solution. This activity is performed below the vacuum at 80–120℃ temperatures. The bleaching of crude palm oil help in removing agents that impact the appearance of the oil. The crude palm oil is originally red because of the presence of carotenes, the addition of acid-activated earth is a great method to neutralize the color of the palm oil. After the bleaching process is through, the red palm oil becomes the golden yellow palm oil, as shown in the picture below, however, the clay and acid are still present in the palm oil.

Filtration

Filtration is the way of catching or materially separating dissolved particulate matter from the oil. As the earth is added into the oil for color neutralizing purposes, after these results are achieved, the clay and acid are to be removed with the help of filtration. Filtration acts as dual clearing action as it not only removes the clay; this process also removes the residues that are realized by the bleaching action. The methods used are generally horizontal and vertical leaf filtering.

Deodorization

The deodorization of the bleached and filtered palm oil is almost the final step in the procedure of obtaining edible palm oil. Heat-crushing and heat-based extraction development are the processes followed to achieve the results. This process helps in the removal of odiferous matter along with aiding the removal of additional secondary unwanted scraps from the fresh palm oil. This action not only gets rid of the strong palm oil smell and impurities but, also helps in elongating the shelf life of the end product. The most popular palm oil deodorizing apparatus applies a combination of 2 methodologies. Inside the deodorizer, the lower section is designed to keep the palm oil at consistent quality, however, the upper part intends to eliminate Free Fatty Acids. Once the oil has been deodorized, and the FFA has been removed, the obtained oil is cooled down with the help of a heat exchanger. While the cooling action is being performed, a solidified product is also derived. This is the Palm Fatty Acid Distillate, also known as PFAD. PFAD is a by-product used in the biodiesel and chemical industry.

At this point, the liquid that is now remaining is the refined palm oil which is also known as Refined Bleached Deodorized Palm Oil (RDBPO). This quality of palm oil is used in commercial food products like baking fats, fats used to bake cookies, and the commercial fried food industry too uses this quality of palm oil. To obtain a more desirable product, the RDBPO goes through one more process called Fractionation. This is how the procedure goes here on:

The fractionation process is a must at this stage as it helps in the separation of solid phases from the liquid phases. The solid-state is called the Stearin and the liquid state is called the Olein. The fluid portion also called the palm olein is becoming very prevalent these days. In tropical climates, the palm olein stays liquids and is quite affordable as compared to other vegetable oils. Fractionation is a thermo-mechanical process that helps in enhancing the quality and range of palm oil products. 

The standard fractionation methods of a palm oil refinery are:

1. Pre-heating- The oil is heated and taken to a certain temperature.
2. Cooling- The cooling process is the most important part. Different palm oil products that are derived in fractionation, cool down and solidify at different temperatures. 
3. Crystallization- After the palm oil cools down, Palm Stearin solidifies and the palm olein stays liquid.
4. Filtering- At the end the with the help of a plate filter the palm olein filtered out. Stearin and Palm olein are stored as two separate products.

The main refined palm oil products obtained from the refining procedure of crude palm oil are:

1. Refined, bleached, deodorized palm oil- More popularly known as the RBD palm oil, this form of the one that is obtained from fractionation. This form of palm oil is completely neutral in all aspects. It is bland, odorless, and it is yellow. This palm oil product stays semi-solid at room temperature. 
2. Palm Olein- This is the liquid achieved after the fractionation of the RBD palm oil. It is obtained after crystallization at room temperatures. It has a restricted array of glycerides and stays liquid at room temperature. RBD palm olein is a well-received palm oil type and is available all over the world in big and small stores. It is popularly utilized as a cooking and frying oil choice in both domestic and commercial kitchens. It is known to be the ideal oil for frying french fries.
3. Palm Stearin- This fraction of refined palm oil is more like a semi-solid fat obtained after the crystallization process. This co-product of palm olein is a truly versatile and popular fully natural fat. It is a well-accepted ingredient in the commercial baking industry in the form of palm oil shortening, baking margarine, and other butter substitutes. One of its highest selling points is its competitive pricing.
4. Palm Fatty Acid Distillate: Popularly known as PFAD, this is a by-product oil in the palm oil refining process. It is highly odoriferous and contains glycerol esters in combination with secondary segments of feedstock. It is lighter brown in tint and stays solid at room temperature. It is a popularly used product in the toilet and laundry soap industry. It is used in making animal feeds and is also utilized as a biofuel.

Beyond these, many more different palm oil products are obtained at different levels of fractionation and crystallization. Here is a detail of products and their properties:

Refined palm oil and nutrition

The nutritional outline of refined palm oil is considerably comparable to different cookery oils available in the market. One tablespoon comprises around 120 calories and the total fat is 14 grams, it includes 7 grams of saturated fat and the content of monounsaturated fat is around 5 grams and the polyunsaturated fat is 1.5 grams.

Palm oil has a high content of tocotrienols, a type of Vitamin E that is full of good antioxidants. It is also suggested that tocotrienols are capable of slowing down dementia and also reducing the risk of stroke. Palm oil is rich in Vitamin A and has also been found to be beneficial for people who struggle with eye or skin difficulty, since they are naturally low on Vitamin A.

The palm oil industry has seen marvelous success when it comes to refining. It is an extremely loved and well-appreciated additive in the commercial food industry. Starting from french fries right to a cone of ice cream everything has one or the other form of palm oil product in it. Difficult to believe, right? Just read that label next time!