The chemistry of degumming for biodiesel production

Degumming is a critically important process for oilseed processors who use their oil in a high-quality biodiesel or in straight vegetable oil fuel. These gums are similar to normal triglycerides; however, one gum chain is a phosphorus with water, meaning that either a normal settling or a water wash followed by settling will get gums out. Some of the gums are non-hydratables, so the oil must be mixed with phosphoric or citric acid to cause the non-hydratable gums to swell up and come out of solution.
The amount of non-hydratable gums formed, as well as the acid content of the oil, will often depend on the oil extraction temperature. Within a certain temperature range, lipases, the enzymes that consume fats and oils, are active during oil extraction. These lipases can cause the free fatty acid(FFA) content or the amount of non-hydratable gums to increase. Higher gum levels and FFA levels are not good for biodiesel production.
Getting the non-hydratable gums out may or may not be critical, depending on the application. For instance, most of the hydratable gums will come out in the glycerin phase in biodiesel production, but the non-hydratable gums that are left over will cause the producer to miss on the phosphorus specification for B100, or 100-percent biodiesel standard.