Hello Dear steemian, hopefully everything still healthy for reading steemit post, today i like to share you a science in cooking oil, certainly all housewives ever use cooking oil when her cooking. So I will explain here about cooking oil was used repeatedly.

I don't know if abroad people use cooking oil repeatedly or only once, but here many of housewife used it repeatedly. Not only housewives, But also fried sellers use cooking oil repeatedly, Thus it color turns to brownish, Why ?

Oxidation of Cooking Oil

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Because, the heating of oil at high temperatures will be lower its quality, it marked by brownish color change, The changing of oil color caused by oxygen damages the unsaturated fatty acids, The oxidation of oxygen occurs when oil was heated or increasing of oil temperature. How to overcome this matter ? Does oil have to be be refrigerated so the oil returns to basic color? Of Course Not. Lets to the point.

Oil is a fatty acid that has been purified through neutralization, degumming, and deodorization process. Generally, the oil qualities determined by fatty acids. Essentially, the fatty acids and oils formed of glycerol condensation or referred as triglycerides (fatty acid molecules). Oil is a fatty acid (triglyceride) that was be as liquid at room temperature and contains many unsaturated acids which can easily to be oxidized. In the frying process the oil serves as conductor media of heating and will undergoes rapid oxidation during heating. The increasing of unsaturated fatty acids of oil caused by contaminated with the air that affected by increasing of temperature, thus the changing of color and decreased of oil quality. The unsaturated fatty acids may also turn into peroxides if it undergoes excessive heating. Some chemical compounds contained in the oil can be seen in the following table.

Used Cooking Oil

Compound	Percentage (%)
Triglycerides	95,4
Free Faty Acid (FFA)	3,1
Water	0,1
Impurities	1,4

^{Data Source : Tofinas, 2010}

Fatty Acid on Used Cooking Oil

Compound	Percentage (%)
Palmitic	95,4
Stearic	3,1
Myristic	0,010
Oleic	0,387
Linoleic	0,105

^{Data Source : Tofinas, 2010}

Purification with Charcoal

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As I have explained before, the activated carbon serves as Absorber, in my last post I mentioned a lot about Activated carbon that used in water purification, but in this post, The Activated Carbon used as cooking oil purification. The active charcoal used for purification of used cooking oil can be made from coconut shell, rice straw etc. The formation of activated charcoal is a pyrolysis process of incomplete burning of organic substance so the carbon compound was not oxidized to be CO2, Where the heating energy could forms carbon molecules that break down into charcoal. The formation of Activated Carbon occurs of heating temperatures above 600^oC and high pressure, thus Activated carbon surface area becomes larger and more effective in absorbing a very small particles.

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Conclusion

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The heated oil will be oxidize so the color turns to brown, the brown color of oil caused by peroxide, the peroxide composed of hydrogen and oxygen in the oil can be absorbed by activated carbon, thus after absorbed the oil color can return to yellow.

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Source

^{Oil and Fat haiyulfadhlie Oil Purification ganggasaunrises Used Oil Cooking repository.usu.ac.id Used Oil Purification ekocahoyono}

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