Quantitation oftransfatty acids in milk fat using spectroscopic and chromatographic methods

Abstract

Trans fatty acids (TFA) formed during biohydrogenation by ruminant animals were quantified in cows' milk fat by means of Fourier transform i.r. (FTIR) spectroscopy. When samples were analysed as the derived methyl esters, a spectral subtraction technique resulted in TFA values that were not biased by the unspecific absorption of intact triacylglycerols or influenced by the shape of the trans band. Austrian milk fat samples contained 20-50 g TFA/kg. Results obtained by analysis of TFA as triacylglycerols compared favourably with those obtained by using methyl esters. The findings of the FTIR method were further substantiated by applying argentation chromatography in combination with capillary gas chromatography to the same set of samples. Besides trans monoenoic acids, non-methylene interrupted cis, trans octadecadienoic acids contributed significantly to the total trans content. Two novel TFA, trans-ll, cis-15 octadecadienoic and cis-d, trans-13 octadecadienoic acids, were identified in milk fat by means of their retention behaviour on argentation chromatography and gas chromatography as well as by an oxidative degradation procedure.

Lipid metabolism in the rumen: New insights on lipolysis and biohydrogenation with an emphasis on the role of endogenous plant factors

“…This hypothesis was supported by identification in milk fat of two novel C18:2 isomers (i.e., trans-11, cis-15 C18:2 and cis-9, trans-13 C18:2) by Ulberth and Henninger (1994). Destaillats et al (2005) characterized cis-9, trans-11, cis-15 C18:3 and cis-9, trans-13, cis-15 C18:3 and concluded that the presence of these FA in rumen fluid, which definitely originate in small quantities from rumen metabolism, confirm the pathway reported in Fig.…”

Quantitative characterization of unsaturated and trans fatty acids in ewe’s milk fat

“…III): trans-9 trans-12, cis-9 trans-13, cis-9 trans-12 and trans-9 cis-12 coeluting with trans-11 cis-15. These isomers were identified by comparing the relative retention times of the chromatographic peaks of the ewe's milk fat samples with the certified vegetable fats and with the milk fat chromatograms analyzed in similar chromatographic conditions in the literature [11,23,29].…”

Influence of the heating temperature on the fat composition of milk fat with emphasis oncis-/trans-isomerization

“…Besides by FAME standards trans D9,trans D12, cis D9,trans D12, trans D9, cis D12 and cis D9,cis D12 (Sigma, St. Louis/Missouri, USA) the identification of trans-C18 : 2-isomers was done according to our earlier studies [35] which essentially were based on the studies of Ratnayake and Pelletier [41] and additionally on the work of Ulberth and Henninger [42].…”