Triglyceride structure of milk fats

Abstract

The enantiomeric nature of the triglycerides of bovine milk fat was reinvestigated by determining the stereospecific distribution of fatty acids in rearranged butterfat, following partial hydrolysis with pancreatic lipase, and in certain molecular distillates of native butterfat, following Grignard degradation. The results with rearranged butterfat confirmed the validity of pancreatic lipase hydrolysis as a means of generating representative diglycerides from milk fat triglycerides. The Grignard degradation and lipolysis gave identical distributions for fatty acids when included as part of the assay system in the stereospecific analysis. Characteristically, butyric acid and the other short chain acids occupied the 3 position in the native butterfat, while in the rearranged oil they were distributed more or less randomly. Gas chromatographic analysis of the short chain glycerides on polyester columns allowed an effective resolution of butyryl, caproyl and caprylyl glycerides of identical numbers of total acyl carbons and double bonds. The method was especially well suited for resolution of the 2,3‐diglycerides, which were recovered either as the more polar fraction from thin layer chromatography of the X‐1,2‐diacylglycerols, or by acetolysis of the residual phenolphosphatides resulting from phospholipase A digestion. It was shown that butyric acid in the 3 position was preferentially paired with myristic, palmitic and oleic acid in the 2 position, and palmitic and oleic acid in the 1 position, which was also characteristic of the other short chain acids.

Molecular weight distribution and regioisomeric structure of triacylglycerols in some common human milk substitutes

“…On the other hand, the fatty acid combinations and regioisomeric structure of specified ACN/DB (acyl carbon number/number of double bonds) species of TAG can be determined rapidly and with minimal sample preparation, which is not easily achieved by other methods. The results obtained for molecular species analyzed by mass spectrometry (7,8) were in accordance with chromatographic results (1)(2)(3)(4)(5)(6).…”

“…In addition to fatty acid combinations, the stereospecific positions of fatty acids within each combination affect the biochemical and nutritional properties of TAG. In human milk, 16:0 is predominantly located in sn-2 position of the TAG molecule, whereas 18:0, 18:1, and 18:2 have been reported to be preferentially esterified in sn-1/3 positions (2)(3)(4)(5)(6). Breckenridge et al (3) reported the molar proportion of palmitic acid to be 16, 58, and 6% of total fatty acids in sn-1, sn-2, and sn-3 positions of human milk TAG, respectively.…”

“…It is well known that fatty acids present in human milk are not randomly distributed in triacylglycerols (TAG) (1)(2)(3)(4)(5)(6)(7)(8). The properties of TAG depend on the fatty acid combination constituting the molecule.…”

Acylglycerol structure of mustard seed oil and of cardiac lipids of rats during dietary lipidosis

“…Intact triacylglycerols and diacv8glycerol s-BDMS ethers were resolved according to molecular weight by glc on 3% OV-1 (24). This glc sys-ten1 was also satisfactory for pyrolysis glc of the sn-2,3-diacylgly~erophosghatidylphenols~ Fatty acid methyl esters were analyzed on coIaamns prepared with 18% EGSS-X and 3% SILAR 5CP as previously described (25).…”

Biosynthesis of triglycerides in freshly secreted milk from goats

“…Analyses were accepted only when the results obtained for positions sn-2 and sn-3 calculated by the alternative procedures agreed within 5% (22). No difficulties were caused by the presence of trigiycerides containing short chain fatty acids as reported by others (23), possibly because the . k 9…”