Physical vs Chemical Refined Edible Oils

How many of us know how the oil is made from its seed or fruits? We use different types of oils in our everyday cooking like groundnut, sesame, sunflower, mustard, palm, olive etc, but hardly care about the process how it is made. We might have come across the terms like monounsaturated or saturated fat but may not even know which is good for health. Our purchase decisions on cooking oil are mostly by watching the advertisements on TV. But to be truthful we do not know how to judge the quality of oil. Well, this article would give you some clarity on how to separate out refined oils.

Typically, oil contains fatty acids, phospholipids, pigments and other components that are unsuitable for usage. Some impurities are naturally present during harvesting while others are formed due to wrong storage methods and oil extraction. Unless these unwanted wastes are removed through some process, they are not suitable for human consumption. There are two ways by which oil can be refined – Physical or Chemical refining. The process by which edible oils are refined (physical or chemical) will determine its quality, color, flavour and taste. Both these methods use different techniques in removing the undesired contents.

Chemical Refining

In this process, first the crude oil undergoes degumming process where it is treated with food grade processing acids or water to remove seed particles, impurities, phosphatides, carbohydrates, proteins and trace of metals. Later to neutralize free fatty acids, it is treated with sodium hydroxide alkaline solution, followed by the washing out of soaps and hydrated phospholipids. Then follows bleaching and deodorization where unwanted pigments, odours and traces of impurities are removed.

Physical Refining

In physical refining process no chemical is added to remove the acids of crude oil. Once the crude oil undergoes degumming process it is sent for steam distillation under vacuum. The process of neutralization using alkaline solution is avoided and steam distillation method is used in the process of deodorization to remove free fatty acids.

Physical vs Chemical Refining

It depends mainly on the free fatty acid (FFA) content of the oil. If FFA content is very low then physical refining is very useful because by using lesser steam, oil can be refined to the purest form. Physical refining methods do not involve any chemicals or soap stocks to remove the FFA content. However, this method doesn’t yield effective results if crude oil quality is low.
In chemical refining soap stocks can hold 50% of the neutral oil. Hence there is a chance of high wastage in this method. Also, care should be taken to maintain balanced temperatures throughout the process. If temperatures are high, the fundamental structure of oil can change by the process called isomerization, which increases trans-fatty acids in the oil. By using chemical refining, maximum reduction of FFA content can be achieved but care should be taken not to exceed the defined temperatures.

Which Oil is Better to Consume?

In chemical refining, oils are exposed to several chemicals, bleaching agents and high temperatures which may lead to many chemical changes that are not good for health. On top of it, many chemicals get added as preservatives to keep the oils for long. For instance, when oil is exposed to high temperatures and low pressures, there could be loss in nutritional value and may also lead to the formation of trans fatty acids that are considered as harmful for heart wellbeing. On contrary, physically refined oils are extracted in a much healthier process without exposure to harsh chemicals or high temperatures. Since they do not lose out on the natural nutritional values, they are much healthier to consume.

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