Influence of the Vegetable Oil Refining Process on Free and Esterified Sterols

The influence of the refining process on the distribution of free and esterified phytosterols in corn, palm, and soybean oil was studied. Water degumming did not affect the phytosterol content or its composition. A slight increase in the content of free sterols was observed during acid degumming and bleaching due to acid-catalyzed hydrolysis of steryl esters. A significant reduction in the content of total sterols during neutralization was observed, which was attributed to a reduction in the free sterol fraction. Free sterols probably form micelles with soaps and are transferred into the soapstock. The steryl ester content remained constant during all neutralization experiments, indicating that hydrolysis of steryl esters did not take place during neutralization. During deodorization, free sterols are distilled from the oil, resulting in a gradual reduction in the total sterol content as a function of the deodorization temperature (220–260°C). A considerable increase in the steryl ester fraction was found during physical refining, probably owing to a heat-promoted esterification reaction between free sterols and FA.