Determination of the glyceride structure of fats; analysis of 14 animal and vegetable fats

The glyceride compositions of seven animals and seven vegetable fats have been determined by GLC analysis of the oxidized esterified glycerides as described in an earlier paper in this series. The compositions determined are compared with those calculated from lipase hydrolysis data according to the method of VanderWal. Good agreement was found between the calculated and determined compositions for the majority of the 14 fats. The exceptions were human fat and the more satu-rated vegetable fats, palm oil and cocoa butter, where some discrepancies occurred. Issued as NRC No. 8052. National Research Council of Canada Postdoctorate Fellow.     

Determination of the glyceride structure of fats. glyceride structure of fats with unusual fatty acid compositions

Five fats containing less common fatty acids, nutmeg butter (myristic), rapeseed oil (erucic, eicosenoic), peanut oil (arachidic, behenic, lignoceric), tung oil (eleostearic), and coriander seed oil (petroselinic) were oxidized, and the oxidized esterified glycerides were analyzed by gas-liquid chromatography (GLC). The values obtained are compared with those calculated from lipase hydrolysis data. Although there was a general over-all agreement between the compositions calculated from lipase hydrolysis data and that obtained by GLC analysis of the oxidized glycerides, there were some discrepancies that exceeded the range of experimental error. 1 Issued as N.R.C. No. 9626.     

Isomerization during hydrogenation of soap: II. Potassium elaidate and potassium linoleate

Potassium elaidate in slightly alkaline solution was hydrogenated for up to 7 hr with 1.5% of Rufert nickel catalyst at 150 C and 20 kg/sq cm pressure. Potassium linoleate was similarly hydrogenated with 1.0% catalyst for 7 hr, and the hydrogenation continued for another 7 hr after addition of 0.5% fresh catalyst. Periodic samples from each were analyzed for component acids. The positional isomers in thecis andtrans monoenes, isolated by preparative argentation thin layer (TLC) or column chromatography, were estimated after oxidation to dicarboxylic acids. Some diene fractions were isolated for further examination. In potassium elaidate hydrogenation,cis monoenes were initially produced in considerable amounts, but to a lesser extent thereafter. Positional isomers were similarly distributed in bothcis andtrans monoenes after prolonged hydrogenation. In the hydrogenation of potassium linoleate, a drop in iodine value (IV) of 60 units occurred in the first hour, and 38% oftrans monoenes (in which the 10- and 11-monoenes constitute 32% each) were formed. The IV then fell only slowly, and up to 38% ofcis monoene (mostly 9- and 12-isomers) was formed. Addition of fresh catalyst caused a major shift ofcis monoenes totrans forms. The diene fraction was mostly nonconjugated material with the first double bond at the 9, 8 and 10-positions. Minor amounts of conjugated dienes were present as well as a dimeric product.     

Determination of the glyceride structure of fats: Anomalous features of the seed fat of bitter gourd (Momordica charantia)

Glyceride composition of the seed fat ofMomordica charantia has been determined by gas liquid chromatography (GLC) of oxidized esterifield glycerides. Stearodiunsaturated glycerides form ca. 80% of the total glycerides. Values obtained by the above method agree closely with those obtained by Youngs' (8) method. However, there is a wide variation between the present results and those calculated according to Vander-Wal (5) from lipase hydrolysis data. Possible reasons for this anomalous glyceride pattern are discussed. Issued as N.R.C. No. 8051.