In this issue

Analysis of oxidized lipids

Detection of oxysterols in oxLDL by MALDI-TOF

Oxidatively modified LDL (oxLDL) is atherogenic by contributing to the formation of the so-called foam cells (lipid-laden macrophages) and contains a number of oxidized and modified lipids including oxysterols. Hasegawa et al. developed a simple method for the detection and rough quantification of oxysterols in oxLDL by MALDI-TOF MS using 2,5-dihydroxybenzoic acid as a matrix. The presented method does not require derivatization or chromatographic separation. The authors first identified the ion peaks of cholesterol and seven major oxysterol species and cholesta-3,5-dien-7-one, a degradation product of 7-ketocholesterol resulting from saponification. Cholesterol, 7-ketocholesterol and cholesta-3,5-dien-7-one give unique peaks and can thus be distinguished from the other oxysterols which show a similar peak pattern. The oxysterol levels can be estimated using isotope labeled cholesterol as an internal standard for quantification.

Analysis of oxidized free fatty acids and acylglycerols

Tarvainen et al. developed a fast UHPLC–ESI–MS method for simultaneous analysis of FFA, MAG, DAG, TAG, and their oxidized equivalents. Effect of the column temperature was studied in order to optimize the separation of closely eluting peaks and to reduce high back pressure. The method was applied to the analysis of total lipid extracts of samples prepared by lipolysis of native, thermally oxidized, and chemically oxidized rapeseed oils mixed with a fat free food as a model of chyme. Over 150 compounds were identified and quantified. The described method is fast, uses very little solvent, and can be applied to the quality control of biodiesel as well as to biological samples in lipidomic and metabolomic studies.

Hasegawa, M. et al., Eur. J. Lipid Sci. Technol. 2011, 113, 423–429

Tarvainen, M. et al., Eur. J. Lipid Sci. Technol. 2011, 113, 409–422

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Production of diacylglycerol-based milk fat analogue

Lubary et al. present a process for the production of a DAG-rich acylglycerol mixture derived from milk fat. This product has potentially interesting nutritional properties resulting from the high content of DAG and short-chain fatty acids. The process consists of three steps: lipase-catalysed partial ethanolysis of milk fat, extraction of the by-product fatty acid ethyl esters using supercritical carbon dioxide, and isomerization of DAG to increase the proportion of 1,3-DAG. Best results were achieved when using immobilized lipase from P. fluorescence.

Lubary, M. et al., Eur. J. Lipid Sci. Technol. 2011, 113, 459–468

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Synthesis of food-grade phytosterol esters of PUFA

Phytosterols, or plant sterols, are steroid alcohols occurring in plants. Some rich sources of phytosterols are wheat germs, sea-buckthorn (see picture), corn and soybean oils. The hypocholesterolemic properties of phytosterols were confirmed in a number of controlled trials. Phytosterols can be ingested as free sterols or in an esterified form, which can provide combined benefits of the sterol and the fatty acid used for the esterification. In addition, the esters are more soluble in fats than the free sterols. Qianchun et al. developed a procedure for synthesis of food grade phytosterol esters of polyunsaturated fatty acids. The authors employed response surface methodology (RSM) to model the reaction. The esterification was catalyzed by sodium bisulfate in the absence of an organic solvent. The mass ratio of PUFA to phytosterols, amount of the catalyst, reaction temperature, and reaction time were optimized with regard to the degree of esterification and oxidative stability of the product. The purity of the product was above 99%. The major species obtained by esterification of β-sitosterol with a mixture of PUFA (linolenic, linoleic, and oleic acid 80:15:5) was β-sitosterol linolenate. This procedure can be applied to produce phytosterol esters for use in functional food formulations.

Qianchun, D. et. al., Eur. J. Lipid Sci. Technol. 2011, 113, 441–449

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