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How does alkali refining remove free fatty acids from crude oils?

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fat and oil processing Butter.

Alkali refining removes free fatty acids from crude oils by treating the oil with an aqueous solution of an alkali, such as sodium hydroxide (caustic soda) or sodium carbonate (soda ash), at temperatures between 40 and 85 °C (104 to 185 °F).1

This chemical treatment causes the free fatty acids to react with the alkali to form an aqueous emulsion of soaps, known as soapstock, which also contains other impurities. In batch refining, this soapstock settles to the bottom of the tank and is drawn off, while in continuous systems, the emulsion is separated using centrifuges. Following this separation, the oil is typically washed with water to remove any remaining traces of alkali and soapstock, then dried through vacuum heating or filtration.1