Identification and occurrence of steryl glucosides in palm and soy biodiesel

A problem of excessive sedimentation was detected in soy and palm biodiesel, preventing the product from complying with requirements on contamination/filterability. The objective of the study was to determine the nature of the sediment by different analytical techniques and to obtain data on the typical range of its components in industrially produced biodiesel samples. The sediment was investigated and the appearance of haze is linked to the presence of free steryl glucosides (FSG) above a certain concentration. This paper focuses on the original analytical approach, taking into account particular physical properties of FSG. Nuclear magnetic resonance and mass spectrometry were used as fast and reliable identification methods, without the need for a prior hydrolysis of the glucosidic bond. A GC method, including optimised sample preparation, was developed for the quantification of the FSG in biodiesel as well as in filter residues. The FSG concentrations in biodiesel produced by different processes ranged between 55 and 275 mg/kg for palm and from not detectable to 158 mg/kg for soy biodiesel.