Francis E. Luddy

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.

Direct conversion of lipid components to their fatty acid methyl esters

SummaryMethyl esters were prepared from cholesteryl esters, phospholipids, and glycerides in substantially quantitative yields by methanolysis with large excess of sodium or potassium methoxide in absolute methanol.A silicic acid chromatographic adsorption column technique was described, which was effective in separating methyl esters from unsaponifiables such as sterols, pigments, etc., and free acids.Conditions for complete methanolysis of glyceride fats and oils requiring only 5 min. of reflux time were described.Quantitative conversion of fatty acids to methyl esters was accomplished by direct esterification with absolute methanol containing 4% HCL or H2SO4 and by methylation with diazomethane.

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).

Analytical13C NMR: A rapid, nondestructive method for determining the cis,trans composition of catalytically treated unsaturated lipid mixtures

Abstract and SummaryHigh resolution natural abundance 13C Fourier transform nuclear magnetic resonance (NMR) has been found to be an effective tool for the rapid and direct determination of the cis/trans composition in partially hydrogenated and isomerized unsaturated lipids. With the eis and trans allylic carbon resonances as representative probes for double bond stereo-chemistry. Evaluation of the cis/trans composition of complex, positionally isomerized mixtures can be made without the necessity of carrying out detailed analyses of multishift olefinic carbon resonances. Migration of double bonds in monoenes and polyenes and formation of conjugated unsaturation in cata-lytically treated fats are discussed and assessed as possible sources of error in the evaluation of cis/trans isomer ratios. Carbon spin lattice relaxation times T1 were measured for both cis and trans allylic reson-ances in isomeric mixtures of varying composition to assure quantitative intensity relationships. 13C NMR compositional analysis of complex mixtures is demonstrated.

Development of edible tallow fractions for specialty fat uses

Edible beef tallow was effectively fractionated by an acetone crystallization procedure to yield five fractions: two solid glyceride fractions comprising 14% (ca. 7% each) of the original tallow; two liquid fractions of 59% and 7%; and one semisolid fraction of 20%. The solid glycerides were composed of ca. 80% saturates (saturated fatty acid glyceride components), approximately an equal mixture of palmitate and stearate, with oleate as the principal unsaturate. The liquid glycerides were composed of more than 65% unsaturates (unsaturated fatty acid glyceride components), predominantly oleate, with the saturates a 3:1 mixture of palmitate and stearate. The semisolid glyceride fraction was similar to cocoa butter. It was one-third unsaturated, mainly oleate with the saturates a mixture of palmitate and stearate. The thermal behavior of the fractions was studied by differential scanning calorimetry. The liquid fraction had a differential scanning calorimetry final melting profile similar to commercial salad oil and the profile of the semisolid fraction resembled that of cocoa butter. The semisolid fraction appeared to be compatible with cocoa butter over a wide range. Mixtures of 5 and 50% cocoa butter with the semisolid fraction had melting profiles similar to that of the original cocoa butter.

Fractionation of lard and tallow by systematic crystallization

SummaryLard and edible tallow were subjected to a series of fractional crystallizations from acetone at temperatures from 20° to -45°C. Six recrystallized precipitate fractions and a filtrate residue were obtained from each fat. In addition to determining the more common physical and chemical characteristics, fatty acid composition of each fraction was calculated from spectrophotometric data, iodine value, and thiocyanogen value. The consistent results obtained throughout by the spectrophotometric method of fatty acid analysis lend further confirmation to the reliability of this method for composition studies of natural fats. The approximate amounts of tri-saturated, di-saturated, mono-saturated, and tri-unsaturated glycerides of the lard and tallow were estimated from the analysis of each fraction on the assumption that not more than two of these classes of glycerides were present in any one fraction. The tallow contains much higher proportions of tri-saturated and di-saturated glycerides and correspondingly lower proportions of the mono-saturated and tri-unsaturated glycerides than does lard. The amount of tri-unsaturated glycerides in lard was found to be significantly greater than meager information in the literature would indicate. The data indicate that the general pattern of glyceride formation in animals such as the pig and cow is probably of random character.

Enzymatic acyl exchange to vary saturation in di- and triglycerides

The reactionrac-glyceryl-1-palmitate-2,3-dioleate(POO) and palmitic acid(P) (excess) → glyceryl-2-oleate-1, 3-dipalmitate(POP) + O catalyzed by porcine pancreatic lipase is a model for the general reactionAAA′’ +A′’ → A′’AA′’ +A.(P,O,A = palmitoyl, oleyl, acyl groups or palmitic, oleic, or fatty acids;AAA′’, etc., are triglycerides). The re-esterification is accom-panied by formation of palmitate-enriched digly-ceride —rac-glyceryl-1-palmitate-2-oleate(PO- OH@#@) exceedsrac-glyceryl-1,2-dioleate (OO-OH) — and glyceryl-2-monoleate (HO-O-OH). Buffer pH optimum for maximumPOO conversion and palmitate enrich-ment in 15 min is between 6.0 and 6.5 at 38 C. Hexane is used to dissolveP in the oil phase. In-creasing the amount of dissolvedP by increasing the amount of hexane added increases palmitate enrich-ment and decreases reaction rate. At 36 C and 6.0 buffer pH (26 volume %POO and 15 volume %P in oil phase), yields after 3 hr werePOP, 22%;PO- OH, 27%; HO-O-OH, 11%;POO, 27%; glyceryl-1,2,3-tri-oleate(OOO), 3%; andOO-OH, 10%.

Effect of deodorization and antioxidants on the stability of lard

SummaryDEODORIZATION produced no appreciable increase in the stability of steam-rendered lard but significantly increased the stability of kettlerendered lard. A substantial increase in the stability of lard was produced by tocopherol, regardless of whether it was added as a pure compound, as a concentrate, or as a tocopherol-bearing oil. Accelerated tests showed that this increase was more than doubled when small amounts of synergists also were added. Deodorization of the lard prior to addition of the synergistic antioxidant compositions produced even greater stability.Nordihydroguaiaretic acid was more effective than tocopherol as an antioxidant for lard, as determined by both the active oxygen and the oxygen-absorption methods. Deodorization of the lard prior to addition of this antioxidant and synergists did not effect further increase in stability over that obtained by the addition of these materials to undeodorized lard.

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.