The oilseed requires undergoing a thorough cleaning process to remove sand, stalk, plant debris and any other foreign matters by rotary or table sieve. Usually, the screening process is assisted by cleaning sieve. Post cleaning, the seeds have to be prepared for efficient oil recovery by pressing. The stages involved are size reduction of the seeds by breaking them and then conditioning the seeds by adjusting their moisture content and temperature, while keeping the seeds hot (say 90-95oc) for a period of 30-60 minute. Then the prepared seed shall be conveyed to the screw oil press machine where it is pressed by the action of worm and outer shell. The crude oil so obtained from the pressing will be first clarified in a settling tank and then shall be pumped through the oil filter machine.

The filtered crude groundnut oil will be pumped to the edible refinery machinery where it shall pass through three stages of refining: neutralization, bleaching and deodorization.

Neutralization : To reduce the level of free fatty acid (FFA) in the oil, caustic soda is mixed with the crude oil and the mixture is fed to a hydration tank. The neutralized oil may have trace of soap which is a by-product of the neutralization process. Therefore, the oil will be washed with water.

Bleaching: The neutralized oil is then pumped to the bleacher in which it is mixed with bleaching earth to improve the color of oil by the process called adsorption. At this stage, any undesirable impurities from the crude Groundnut oil are removed. This process improves the initial taste, final flavour and oxidative stability of the product. The bleached oil is then filtered to remove the bleaching earth leaving the oil with very low phosphorous levels and no soap.

Deodorization :  The bleached oil, after being filtered, will be pumped to the deodorizer to avoid substances which are responsible for the odor of edible oil.

Neutralized oil is drawn into the second vessel called bleacher where color of oil is eliminated by bleaching process with aid of chemicals such as carbon black and bleaching earth. Oil is generally heated up to 110 Centigrade by thermic fluid coils. Stirring is also continued. Bleaching process is done under vacuum.

Then bleached oil flows to the filter press where bleaching earth and chemicals are separated and then clean bleached oil will be drawn to deodorizer where oil is heated above 110 Centigrade through thermic fluid coils and then live steam is given to the oil from the bottom steam nozzles and temperature of oil is raised up to 200 to 220 Centigrade through thermic fluid coils. The entire process happens under high vacuum. The odor of the oil will be removed. Then it goes to cooler where water circulating coils take away heat and oil is cooled. Again it goes to second filter press where completely refined and transparent color less oil is obtained.

In the refining process, Thermic Fluid Boiler, Vacuum Pump, Barometric Condenser, Catchols, Steam Generator have their particular roles.These equipments are connected with the vessels through pipelines as part of the refinery.

When refining edible oil there are a number of steps that need to be followed with the first one being distillation. During distillation, the oil is heated until the chemical solvents that were used in extraction evaporate. The next step is degumming which involves the removal of gums as well as solvents that can dissolve in oil, by passing water that is hot throughout the oil to remove impurities. The third step is neutralization where the oil is treated using sodium hydroxide to remove waxes, fatty acids, pigments among others.

Bleaching is another step which is done using high-activity clay removes components that are “off-colored” from the oil. The clarity of the oil, especially those that will be refrigerated is done through a step known as dewaxing. Deodorizing involves the evaporation of compounds that are unstable by using steam that is of high pressure in treatment. Edible oils also need to be preserved and this step involves the use of BHA or BHT. Finally, filtration is the last step which helps remove large impurities but without the use of chemicals.

The process that the palm fruits are put through to be able to extract as much oil as possible begins with sorting. Here, the palm fruits that are not of the required quality are separated from the rest and disposed. The palm fruits that are of good quality are taken to the processing plant and are taken to another stage known as the conveyer system. At this stage the fruits are split into pieces that are much smaller before they are ushered into a cage where they are sterilized. The sterilization process removes any impurities making them ready for the rest of the production process. After sterilization, they are moved onto the threshing drum where the flesh is separated from the husks, then moved to the digesters. They are eventually placed in the presser where the extraction of the oil takes place but in a crude form.

The crude oil is then clarified and then dried before it goes through the palm oil refinery process. The process ensures that there are no impurities in the palm oil and it can now be used in many ways without the fear of infection because of any type of contamination.

In conclusion, Oil refinery process is important in making the vegetable oil safe for human consumption.