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ARS Home » Research » Publications at this Location » Publication #110629


item Eller, Fred
item King, Jerry

Submitted to: Annual Meeting and Expo of the American Oil Chemists' Society
Publication Type: Abstract Only
Publication Acceptance Date: 4/25/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: The purpose of this research was to develop an accurate gravimetric fat determination method for ground beef by comparison of gravimetric and gas chromatographic fatty acid methyl ester (GC-FAME) determinations of supercritical CO2 (SC-CO2) extracts. Previous work using ethanol as a co-solvent produced high gravimetric estimates of fat content, especially for low-fat ground beef samples. Given the high moisture content of groun beef and the slight solubility of water in SC-CO2, it is probable that the co-extraction of water with the fat led to the high gravimetric results. In an attempt to bring the gravimetric and GC-FAME estimates into closer agreement (i.e., eliminate the water from the gravimetric determination), the effects of ethanol modifier, sample drying (before extraction and after collection) and the use of drying agents within the extraction cell were studied. The use of ethanol as a co-solvent led to high gravimetric results regardless of whether the sample was dried before extraction, afte collection, or not dried. Neat CO2 gave essentially equal gravimetric and GC-FAME results. Although drying the sample prior to extraction reduced the co-extraction of water, this also decreased the amount of fat that was extracted. Drying after collection led to only a small difference between the gravimetric and GC-FAME determinations when neat CO2 was the solvent. Using either molecular sieves (3 angstroms) or silica gel led to both low gravimetric and GC-FAME results. Collection efficiency increased as the amount of fat increased. In addition, the apparent collection efficiency also increased as post-extraction equilibration time increased from 5 to 35 minutes, although the difference was less pronounced at the higher levels of fat.