Grasas y Aceites, Vol 59, No 1 (2008)

Analysis of used frying fats for biodiesel production

M. V. Ruiz-Méndez
Instituto de la Grasa (CSIC), Spain

S. Marmesat
Instituto de la Grasa (CSIC), Spain

A. Liotta
Instituto de la Grasa (CSIC), Spain

M. C. Dobarganes
Instituto de la Grasa (CSIC), Spain


Used frying fats and oils with highly variable and uncontrolled quality are used for the production of biodiesel . The objective of this study was to define the analytical methods useful to obtaining information on the quality of the used frying oils as raw material for biodiesels as well as for the characterization of the biodiesels obtained from them. Twentyfour used frying oils from restaurants and domestic fryers were analyzed before and after transesterification to fatty acid methyl esters (FAME). From a detailed analysis of the samples by means of a combination of adsorption and size exclusion chromatography, the quantitative importance of polymeric compounds was deduced both from the direct analysis of the oils and from their FAME. Excellent linear correlation between polar compounds and polar FAME (R=0.9768) was found. The possibilities of interferences from polar fatty acid in the standard method to determine the ester content are defined. Finally, determination of non-polar FAME by silica column is proposed as a good alternative to the gas chromatography method.


Analysis; Biodiesel; Polar compounds; Polar fatty acid methyl esters; Used frying oils

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