The present invention relates to a method for reducing the amount of steryl glycoside in an oil or fat (e.g. a biofuel substrate) and/or a biofuel, the method comprising admixing one or more enzymes with an oil or fat comprising steryl glycoside; such that said one or more enzymes degrades the steryl glycoside. The one or more enzymes is preferably an enzyme which is capable of hydrolysing the glycosidic bond in a steryl glycoside. Suitably the enzyme may be a glycosidase enzyme and/or a β-glucosidase and/or an amyloglucosidase.