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ARS Home » Research » Publications at this Location » Publication #74494


item Snyder, Janet
item King, Jerry
item Jackson, Michael

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/14/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Quick, solvent-free analytical methods are needed for analysts to monitor the requirements of the Nutritional Labeling and Education Act. The fat content of oilseed and meat samples has been determined employing a technique which utilizes high pressure extraction with carbon dioxide and enzyme-catalyzed reaction in place of the traditional solvent-based methods. Oilseed and meat samples yielded the highest fat values when the samples were freeze-dried before utilizing the extraction/reaction method. Also, minor constituents, cholesteryl esters and phospholipids, present in meat and oilseeds were successfully extracted and analyzed with this method. The described procedure can be used as a rapid method to analyze for total fat content in foods; it is of interest to scientists and regulators monitoring fat content for nutritional labeling.

Technical Abstract: The fat content of lipid-containing samples has been determined employing a simultaneous extraction of the fat with supercritical carbon dioxide followed by an enzyme-catalyzed methylation of the fat, under supercritical conditions, prior to GC analysis. This study was initiated to determine the effect of moisture content on the extraction and conversion of lipids in oilseed and meat samples to their fatty acid methyl ester (FAMEs) derivatives. These samples were freeze-dried or mixed with Hydromatrix and compared with control, untreated samples employing the above-described SFE-reaction sequence. Particular attention was focussed on minor constituents, such as phospholipids and cholesteryl esters, to see if they could be extracted and derivatized using the above technique. Recoveries and reaction conversions of the lipid species were determined with the aid of gas chromatography, high performance liquid chromatography, and supercritical fluid chromatography for the analyses of the extracted lipids. Total fat values were higher from the freeze-dried meat and oilseed samples than from samples mixed with Hydromatrix or left untreated. Extraction of cholesteryl esters was greater than 90%, and conversion of the cholesteryl esters to FAMEs was 93% or higher. Extraction of phosphatidic acid was only 85% compared to more than 90% recoveries for the other phospholipid species. FAME conversion was greater than 96% for all of the phospholipid samples in the study.