Determination of phytosterol oxides in some food products by using an optimized transesterification method

An increased intake of phytosterols (PS), as well as new products launched on the market enriched with PS and phytostanols, increases the demands for improved analytical techniques. In the present study, a method for the determination of phytosterol oxidation products (POP) was evaluated and optimized. The method included transesterification, enrichment with amino SPE cartridges and quantification by GC. The methodology was evaluated with authentic samples of sito-, campe- and stigma-sterol oxidation products and the linearity and recovery for some POP were > 0.95 and 80-120%, respectively. The lowest spiking level determined was 0.5 mu g and lower levels could be quantified. In addition, the formation of POP during thermal oxidation of vegetable oils at 180 degrees C for 0-2 h was studied and increased levels were observed. A commercially available PS ester-enriched margarine was also included in the investigation and the level of POP was 12 mu g/g of spread. (c) 2005 Elsevier Ltd. All rights reserved.