Paul Magidman

Pancreatic lipase hydrolysis of triglycerides by a semimicro technique

Procedures are described for rapid lipase hydrolysis of triglycerides, isolation of the hydrolytic products by TLC and their conversion to methyl esters and fatty acid analysis by GLC. The techniques are applicable to a few mg of triglycerides or fats. Examples of data obtained with purified triglycerides indicate that the specific action of pancreatic lipase for the 1,3 ester groups is nearly absolute and the technique may be used as a criterion of purity of di- and tri-acid triglycerides. Ca. 83% of the palmitic but only 10~12% of stearic and C18 unsaturated acids of commercial lard occur in 2-position.

A rapid and quantitative procedure for the preparation of methyl esters of butteroil and other fats

A simple and convenient method for the quantitative preparation of methyl esters of fatty acids from glyceride fats and oils is described. The procedure, using potassium methylate as catalyst and a heating interval of 2 min at 65C in a closed vial, is applicable to fats containing both low and high molecular weight fatty acids such as butteroil. The methyl esters of samples ranging from a few mg to 30 mg are isolated by CS2 extraction and a TLC technique. A similar procedure using sulfuric acid in methanol as catalyst is described for the conversion of free fatty acids to methyl esters. For the routine analysis by GLC of fats and oils such as lard, tallow, soybean, cottonseed oil or butteroil, no isolation of the methyl ester is required. A CS2 extraction carried out in the reaction vial allows the GLC analysis immediately after the reaction period (2 min).

Fatty acids of cows' milk. A. Techniques employed in supplementing gas-liquid chromatography for identification of fatty acids

Milk fat methyl esters were subjected to distillation and silicic acid column chromatography to provide fractions of less complexity for gas-liquid chromatographic analysis. It was still necessary however to employ supplemental techniques for identification. Chromatograms were obtained with polyester columns of different polarity on all the fractions and necessary reference samples. While many of the components were identified in the usual way by plots of relative retention time versus number of carbon atoms, iodine values for total unsaturation and ultraviolet spectrophotometry for conjugated and nonconjugated polyunsaturated acids were essential for positive identification of some components. Similarly, examination by infrared spectrophotometry confirmed the presence or absence of conjugated diene ascis-trans, trans-trans or both. Isolatedtrans or terminal double bonds were also determined in this way. Gas-liquid chromatograms of some fractions showed incompletely resolved peaks attributable to the presence of methyl esters of odd-carbon atom, branched-chain, and unsaturated acids. Hydrogenation and rechromatographing provided more positive determination of the structure of these components. Further confirmation of identity of some peaks on the chromatogram was achieved by collection of the appropriate fractions and examination of the collected material. At least 60 fatty acids were identified, including several not previously reported, such as odd-numbered carbon chain length monoethenoid acids from C15 to C23.

Analysis of fats and oils by gas-liquid chromatography and by ultraviolet spectrophotometry

Summary1.Known mixtures of pure fatty acid methyl esters and a number of fats and oils as their methyl esters have been analyzed by conventional GLC with thermal conductivity detectors.2.Percentage of fatty acid distribution determined by GLC agreed well with known percentages in model mixtures and with analysis by the spectrophotometric method for fats and oils.3.Determination of very small amounts of arachidonic and pentacnoic acids in lard by GLC was not successful.

Reduction with zinc of triple bonds tocis double bonds in long chain conjugated fatty acids

The methyl ester of santalbic acid (trans-11-octadecen-9-ynoic acid) was hydrogenated with powdered zinc in 50% propanol to yield 90% of thecis,trans-diene ester; similarly, 7,9-octadecadiynoic methyl ester was converted tocis,cis-diene ester but yields were no better than 75%.

Effect of catalytic treatment with sodium methylate on glycerine composition and properties of lard and tallow

SummaryTreatment of lard with sodium methylate did not affect fatty acid composition nor the usual chemical constants and melting points. The glyceride composition however was altered considerably and showed close agreement with values calculated for random distribution. This change in glyceride composition was accompanied by significant changes in physical character as shown by consistency numbers, dilatometric and micropenetration measurements, and cooling curves.Beef tallow remained almost unaffected by the sodium methylate treatment. The glyceride composition before and after treatment as determined by Karthas method agreed well with values calculated for random distribution. Only the cooling curves indicated any change induced by the treatment.

Glyceride distribution in adipose and liver glycerides of animals

The glyceride distribution in depot fats from a series of animals was determined by pancreatic lipase hydrolysis, isolation of hydrolytic products by thin-layer chromatography (TLC), and fatty acid analysis by gas-liquid chromatography (GLC).Distribution of the principal types of glycerides (S3, S2U, SU2 U3) in the internal and external adipose tissue fats from the same pig was nonrandom. The percentages of palmitic acid at the 2-position in these adipose fats were comparable. However, liver glycerides from this same animal differed strikingly from adipose glycerides, having, for example, only ca. 15% of its palmitic acid in the 2-position compared with > 80% for adipose fats. The liver glycerides of lamb, rabbit, and dog also differed considerably from adipose glycerides in glyceride distribution and in percentages of individual fatty acids in 2-position.The composition of adipose glycerides from Lamb, beef, deer, rabbit, chicken, and dog in terms of the four principal glyceride types approached closely the values calculated for random. When positional isomers were considered, however, only the adipose glycerides of the dog conformed to random distribution.

Alcoholysis ofVernonia anthelmintica seed oil and isolation of methyl epoxyoleate

The methyl esters ofVernonia anthelmintica seed oil were prepared without oxirane destruction by methanolysis using potassium methylate as catalyst. A single crystallization of the methyl esters from petroleum ether at −60C was found to be a convenient means of preparing large samples of methyl epoxyoleate of 93.6% purity in 92% of theory yield as based on oxirane titration. Further purification was achieved by recrystallization from petroleum ether at −40C to give a product at 97% purity in 54% of theory yield. Gas-liquid chromatography and thin layer chromatography along with associated techniques were employed to obtain the fatty acid composition of the crystallization fractions. Fifteen fatty acid methyl esters, including the methyl 12,13-epoxyoleate were identified.

Fatty acids of lard. B. Quantitative estimation by silicic acid and gas-liquid chromatography

A quantitative comparison was made of the fatty acid composition of a commercially rendered lard, a laboratory rendered lard, and a solvent extracted lard representing the same batch of pig tissue. The composition was determined by a preliminary separation of the methyl esters on a silicic acid column floowed by gasliquid chromatography of the fractions containing a known added amount of reference compound. This technique permitted estimation of the composition of each fraction and subsequent calculation of percentage of the minor as well as the major components in the original lard. It was concluded that the minor components were not artifacts produced in rendering.

Color and the lipid composition of pork muscles

The lipid characteristics of three porcine muscles were investigated. Included in the study were the light and dark portions of the semitendinosus muscle, the semimembranosus (light) and the quadriceps femoris (dark) muscles. The lipids from the semimembranosus and the quadriceps femoris muscles were observed to be statistically different. The light muscles were 20% higher in lipid level and these lipids contained 20% more glycerides and 40% less phospholipids than the dark muscles. The glycerides from both muscle lipids were identical in fatty acid composition but the phospholipid fatty acids differed significantly. The light muscle phospholipid fatty acids were higher in monoenes while the dark muscle phospholipids predominated in polyunsaturates. In the semitendinosus muscle, the light portion was 35% higher in lipid content than the dark portion but the compositions of the lipids from both areas were similar. When these data were compared to the values for the semimembranosus and the quadriceps femoris muscle lipids, the lipid characteristics were found to be intermediate of predominantly light or dark muscle lipids.