Alan J. Sheppard

Comparison of methylene chloride and chloroform for the extraction of fats from food products

Ten food products with a wide range of total fat, fatty acid and sterol content were obtained from a supermarket in the Washington, DC area. These food products were extraced by a new method, using methylene chloride/methanol as the extraction solvent. The results were compared to the Folch et al. procedure, in which chloroform/methanol is the extraction solvent. Total fat was determined, and fatty acid methyl esters and sterol butyrates were prepared and measured by gas liquid chromatography. An analysis of variance indicated that methylene chloride is as effective as chloroform, a suspected carcinogen, in the Folch et al. extraction of total fat, fatty acids and sterols from foods.

Determination of fatty acids in butter fat using temperature-programmed gas chromatography of the butyl esters

Abstract Substituting n -butanol for the methanol specified in the AOAC Official methods of analysis (sections 28.056–28.059) yields the butyl esters of the fatty acids with complete recovery of the volatile short-chain acids. Fatty acid butyrates can be determined using a continuous multistage temperature-programmed gas chromatographic method, with a 10% apolar 10C column. The results of the analysis in 1982, of fifty butters were compared with those of thirty butters analyzed in 1974. There were no practical significant differences in the fatty acid compositions of the 1974 and 1982 butters. A urea fractionation technique was used to concentrate minor components for identification and estimation.

Comparison of various methods for the extraction of total lipids, fatty acids, cholesterol, and other sterols from food products

Abstract and SummarySeven methods were used to compare the efficiency of total lipid extraction from 13 samples of eight different food products. The methyl esters of fatty acids and the butyrate esters of sterols were prepared and analyzed by gas liquid chromatography. On the basis of total lipid recovered and amounts of fatty acids and sterols present, a chloroform: methanol procedure was selected as the most effective method.

Composition of Selected Dietary Fats, Oils, Margarines, and Butter

Fats and oils provide the most concentrated source of energy in the diet, about 9 kcal/g. Animal tissues, dairy products, and oils extracted from certain seeds contribute most of the fat in the diet (see Table I). The source, chemical nature, and processes that fats and oils are subjected to before they reach the market shelf are important aspects of the study of lipids. A fat is distinguished from an oil by its solid state at a particular temperature, usually room temperature. Some oils are winterized to remove triglycerides that would cause the oil to solidify in the refrigerator; other oils are lightly hydrogenated to convert highly unsaturated fatty acids to more saturated acids to prevent the development of off-flavors and rancidity.

Gas chromatography of the fat-soluble vitamins: A review

The application of gas liquid chromatography (GLC) as an analytical tool for the determination of the fat-soluble vitamins A, D, E and K has yet to be utilized to its full potential. A review of the published work of many researchers in this field is presented. GLC methods to measure the vitamin A isomers have not been developed to any appreciable practical extent. Liquid liquid chromatography might well be the technique of choice. In the field of vitamin D there are indications that a practical GLC analysis is feasible for pharmaceutical preparations. The GLC applications for vitamin E are diverse, well defined and generally widely accepted in research laboratory situations and for regulatory and quality control usage. Vitamins K1 and K2 have been measured with limited success in a few research laboratories, but the GLC methods have not developed on a practical basis. However GLC is used for measuring vitamin K3 (menadione and menadione sodium bisulfite) on a fairly routine basis in quality control laboratories.

Evaluation of eight extraction methods and their effects upon total fat and gas liquid chromatographic fatty acid composition analyses of food products

Samples of corn beef hash, frozen turkey pie, frozen beef pie, and beef stew were extracted by eight methods. Methyl esters of the fatty acids contained in the extracted fat residue were prepared with BF3-methanol reagent and measured quantitatively by gas liquid chromatography. A 4N HCl digest followed by ethyl ether extraction was the most effective extraction method. Total lipid extracted, fatty acid distribution, and triglyceride recovery were the primary evaluation criteria. Recovery studies were carried out on eight different foods ranging from high meat content to pure vegetable shortening.

Comparison of the clearances of serum chylomicron triglycerides enriched with eicosapentaenoic acid or oleic acid

Rat mesenteric lymph chylomicrons containing triglycerides enriched with either [14C]oleic acid (OA) or [14C]-eicosapentaenoic acid (EPA) were prepared by ultracentrifugation of lymph samples collected for 6 hr after a single duodenal infusion of an emulsion containing either fatty acid. These chylomicrons were injected into the jugular vein of recipient rats and, at various time intervals, blood was drawn and serum was assayed for radioactivity. In separate animals, serum lipoprotein fractions were separated by ultracentrifugation, and the redistribution of labeled fatty acid among circulating lipoproteins was determined by liquid scintillation spectrometry. When the early disappearance rates (10 min) of either total serum radioactivity or specifically the chylomicron fraction were compared, there were no differences between the groups receiving OA-or EPA-enriched chylomicrons. However, disappearance rates of EPA-enriched chylomicrons were slower than those of OA-enriched chylomicrons from 25 to 90 min. The small but significant differences in the disappearance rates for the longer time periods cannot be ascertained without further studies. At 5 min after injection of either type of chylomicron, the d<1.006 g/ml lipoprotein fraction of serum chylomicrons and very low density lipoproteins contained almost 90% of the original radioactivity. By 240 min, when less than 2% of the radioactivity remained, this radioactivity in the d<1.006 g/ml fraction was 43–46%, with concomitant increases in the low and high density lipoprotein fractions and in the lipoprotein-free serum.

In vitro clearance of chylomicron triglycerides containing(ω-3) eicosapentaenoate

Abstract Rat mesenteric lymph chylomicrons, containing triglycerides enriched with either [ 14 C]oleic acid or [ 14 C]eicosapentaenoic acid, were prepared by ultracentrifugation of lymph samples collected for 6 h after a single duodenal infusion of an emulsion containing 0.3 mmol of either fatty acid. After determination of protein and of total fatty acid content and composition, enriched chylomicrons were suspended in Krebs-bicarbonate buffer. Non-working hearts were perfused in a recirculating system for 45 min using the enriched chylomicron preparations. At 15 min intervals during perfusion, the media were assayed for total radioactivity, 14 CO 2 and 14 C-labeled fatty acids associated with triglycerides, unesterified fatty acids, phospholipids, mono- and diglycerides. After perfusion, the hearts were extracted and assayed for total lipid radioactivity and isotope distribution among heart lipid fractions. With this membrane-supported lipoprotein lipase system, clearances of chylomicron triglycerides containing either fatty acid were identical, as were the myocardial uptakes of the fatty acids and oxidations to 14 CO 2 . Furthermore, except for a significantly greater incorporation of eicosapentaenoate into myocardial phospholipids, tissue isotope distributions of the two labeled fatty acids were also the same. These studies suggest that at least the initial phases of peripheral clearance of chylomicrons enriched in ω-3 fatty acids is as efficient as with those containing oleate.

Sample size influence on boron trifluoride-methanol procedure for preparing fatty acid methyl esters

Sample size influences the yields of methyl esters of fatty acids by the boron trifluoride-methanol method. A study of the method revealed that best recoveries are obtained by using a minimum of 350 mg of lipid extract to prepare the methyl esters.

Suitability of lipid extraction procedures for gas-liquid chromatography

A comparison of two methods of extracting liver tissue lipids has been made using a limited amount of experimental material. The extracts prepared by a procedure using Bloor’s reagent were more stable in storage, contained nearly 100% more total lipids and phospholipids, and produced more uniform and reproducible patterns on gas chromatographic analysis, than extracts of the same liver prepared by a diethyl ether Soxhlet extraction.