Determination of Waxes in Olive Oils using Silver Nitrate-Impregnated Silica Gel

CARELLI, AMALIA; BAÜMLER, ERICA; MARTA GONZALES; LILIANA CECI

Rotterdam, Holanda

Congreso; Euro Fed Lipid Congress. Oils, Fats and Lipids for a Healthy and Sustainable World; 2011

Euro Fed Lipid

Determination of Waxes in Olive Oils using Silver Nitrate-Impregnated Silica Gel Amalia A. Carelli*, Erica R. Baümler, María T. González and Liliana N. Ceci, PLAPIQUI (Universidad Nacional del Sur-CONICET), Bahía Blanca, Argentina The sum C40, C42, C44 and C46 aliphatic waxes is a parameter used to detect pomace-olive oil in virgin olive oil. This sum has been regulated as: < 250 mg/kg for edible virgin olive oils. It has been showed that very good quality extra virgin olive oils contain fatty acid ester with diterpenic alcohols that are quantified simultaneously with aliphatic waxes by IOC method (COI/T20/Doc No. 18/Rev2). This method is based on the oil fractionation by chromatography on a hydrated silica gel column followed by direct analysis by capillary gas chromatography with on-column injection. In this work, it is evaluated the introduction of a double-adsorbent layer of hydrated silica gel and silver nitrate-impregnated silica gel in the column chromatography step in order to obtain a wax fraction free of non-aliphatic waxes. Recovery of standards of waxes (C34-C44) by CC-GC using silver nitrate with C32 as internal standard yielded percentages higher than 90%. In addition, the chromatographic profiles of crystallized sunflower wax (prepared by solvent purification of a winter cake) obtained both by direct injection and by CC-CG using silver nitrate were similar. The analysis of olive oil samples by means of the proposed method yielded wax contents 20-50% lower than IOC method with variation coefficients less than 5% (n=4). In conclusion, the use of a double-adsorbent layer of hydrated silica gel and silver nitrate-impregnated silica gel in the column chromatography step allowed obtaining repetitive results and quantifying only aliphatic waxes.