Crude oil obtained by screw pressing and solvent extraction of oilseeds will throw a deposit of so-called gums on storage. The chemical nature of these gums has been difficult to determine. They contain nitrogen and sugar and can start fermenting so they were at one stage thought to consist of glycolipids and proteins. Now we know that these gums consist mainly of phosphatides but also contain entrained oil and meal particles. They are formed when the oil absorbs water that causes some of the phosphatides to become hydrated and thereby oil-insoluble. Accordingly, hydrating the gums and removing the hydrated gums from the oil before storing the oil can prevent the formation of a gum deposit. This treatment is called water degumming. It is never applied to fruit oils like olive oil and palm oil since these oils have already been in contact with water during their production.
Water degumming is the oldest degumming treatment and also forms the basis of the production of commercial lecithin. I use the term ‘commercial lecithin‘ here to make a distinction from the use of the word ‘lecithin’ as the trivial name for the compound phosphatidylcholine (PC). Similarly, phosphatidylethanolamine (PE) has the trivial name ‘kephalin’. Since the water degumming process involves more water than when crude oil is allowed to absorb moisture from the atmosphere, the gums resulting from the water degumming process also remove hydrophilic substances such as sugars from the oil.