Quantification of free and esterified steryl glucosides in vegetable oils and biodiesel

Abstract

Steryl glucosides (SG) are minor components that dramatically modify the low temperature performance of fatty acid methyl esters (FAME) used as biodiesel. SG are naturally present in vegetable oils but they may also be the result of the transesterification of esterified steryl glucosides (ESG). These are present in vegetable oils at a level of a few hundred milligrams per kilogram, depending on the nature of the feedstock. We developed an analytical method to quantify SG and ESG in vegetable oils and in FAME. The purification of SG and ESG was performed by liquid chromatography on silica gel, and the analysis of the trimethylsilyl derivatives was achieved by gas chromatography and flame ionization detection. The filterability of biodiesel is affected when the SG content is higher than 20 mg/kg. Therefore, the sensitivity of this new method is adapted for this purpose since the quantification limit is 10 mg/kg of SG and ESG. The recoveries are acceptable, between 75% and 90% depending on the species and content, and the reproducibility relative standard deviation, evaluated at 10%, is comparable to other studies.

Characterization of insoluble material isolated from Colombian palm oil biodiesel

“…2C), and was attributed to stretching of eC¼O belonging to the fatty acid chain esterified with the glucoside moiety of ASG [2]. Since ASG have been demonstrated to coelute with FSG when biodiesel is purified by column chromatography [8], this finding suggested the presence of ASG in F2Hz1.…”

“…Precipitate is soluble in pyridine, dimethylsulfoxide [2], dimethylacetamide, and methylpyrrolidone [8], which have high boiling point and are inappropriate to be used in fractionation by column chromatography. 1 mg of pellet was tried to be dissolved in 1 mL of solvent.…”

“…This was a critical task because of the limited solubility of biodiesel precipitate in most organic solvents [8].…”

“…FSG are glycosylated steryl derivatives naturally present in vegetable oils [8]. Because of their low solubility in biodiesel, researchers have reported that FSG are the main cause of precipitate formation [2,8,9].…”

On the Presence of Steryl Glucosides in Virgin Olive Oil and their Relationship with other Minor Compounds: Untangling the Skein

“…This molecule can be esterified to a fatty acid at the C6' position, giving rise to ESG (Gómez-Coca et al, 2013). The role of both kinds of phytosterol derivatives is still unclear (Grille et al, 2010), although a number of relevant studies are being carried out both in biodiesel (Bondioli, 2009;Lacoste et al, 2009) and in edible matrices other than olive oil (Nyström et al, 2012;Münger & Nyström, 2014).…”