About water degumming and the hydration of non-hydratable phosphatides

Although we have been degumming and neutralizing oils for over a century, we still do not know the mechanisms of these reactions in detail. The present “Hypothesis Paper” reviews a number of outstanding questions, raises a number of further questions but also provides some answers. The main outstanding question concerns the hydration of phosphatides during water degumming: is this thermodynamically or kinetically controlled? Crucial experiments show it to be controlled by the thermodynamically determined partition coefficients. One of the further questions concerns the compounds present in oil that contain phosphorus but differ from the known phosphatides. One of the suggested answers concerns the “charge balance” of the water degumming process. By assuming that the phosphatidic acid that is removed during water degumming is removed as its potassium salt and that the calcium that is removed is removed as calcium soap, the positive and negative charges involved in the water degumming process can be made to balance. The paper also confirms that complete removal of phosphatides requires a really strong and concentrated base Practical applications: Almost all oil produced worldwide is either degummed or neutralized or both. Gaining insight in the chemistry involved must surely lead to practical applications and savings which, given the scale of operation, will be quite substantial. Crude oil contains various phosphatides that are removed during the degumming and the refining processes. It has now been found that this removal is thermodynamically controlled rather than kinetically as reported in the literature. The removal of non-hydratable phosphatides on prolonged exposure to water has been found to be by autocatalytic hydrolysis. It has also been found that by assuming that the calcium that is removed during water degumming leaves the oil as calcium soaps, the positive and negative molecules that disappear on degumming are in balance. Even so, the question by what mechanism the non-hydratable phosphatides are removed during alkali refining still has to be resolved.