Hostname: page-component-cd9895bd7-jkksz Total loading time: 0 Render date: 2024-12-28T00:30:01.278Z Has data issue: false hasContentIssue false
  • English
  • Français

Isomerisation of cis-9 trans-11 conjugated linoleic acid (CLA) to trans-9 trans-11 CLA during acidic methylation can be avoided by a rapid base catalysed methylation of milk fat

Published online by Cambridge University Press:  04 August 2008

Michael R F Lee  and
John K S Tweed
Michael R F Lee*
Affiliation:
Animal Science Programme, Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth, Wales, SY23 3EB, UK
John K S Tweed
Affiliation:
Animal Science Programme, Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth, Wales, SY23 3EB, UK
*
*For correspondence; e-mail: mcl@aber.ac.uk
Get access Rights & Permissions [Opens in a new window]

Abstract

This study investigated the evolution of trans-9 trans-11 conjugated linoleic acid (CLA) from cis-9 trans-11 CLA during methylation and its avoidance through a rapid base methylation of milk fat. The study examined three conditions shown to result in loss of cis-9 trans-11 CLA during methylation namely: temperature, methylation time, water contamination in old reagents and acidic conditions. Three techniques currently used for the conversion of milk fat into fatty acid methyl esters for analysis of CLA content by gas liquid chromatography and a fourth procedure designed to eliminate acidic conditions and to limit methylation temperature and time were used. The four methods were: (i) acidic methylation (AM); (ii) acidic and basic bimethylation with fresh reagents (FBM); (iii) acidic and basic bimethylation with pre-prepared reagents (PBM) and (iv) basic methylation (BM). Each regime was carried out on six milk samples over two periods and methylated 1 ml freeze-dried milk (n=12 per regime). Total CLA was not different across methylation regimes (0·30 mg/ml). Isomer cis-9 trans-11 was higher (P<0·01) with BM than the other regimes and lowest with AM: 21·2, 17·8, 18·8 and 14·7 mg/100 ml for BM, FBM, PBM and AM, respectively. The inverse relationship was shown for trans-9 trans-11 with higher (P<0·001) amounts with AM than the other regimes and lowest with BM: 0·57, 2·55, 2·36 and 3·69 mg/100 ml for BM, FBM, PBM and AM, respectively. The trans-10 cis-12 isomer was also shown to alter with methylation procedure being higher (P<0·001) with AM than the other regimes: 0·43, 0·47, 0·29 and 1·20 mg/100 ml for BM, FBM, PBM and AM, respectively. Validation with known CLA free fatty acid and triacylglycerol standards confirmed that AM resulted in conversion of cis-9 trans-11 to trans-9 trans-11, and also elevated trans-10 cis-12 whilst BM of triacylglycerol CLA did not isomerise cis-9 trans-11 and was comparable to FBM.

Keywords

Conjugated linoleic acidmilk fatbase methylationtrans-9 trans-11 CLA isomercis-9 trans-11 CLA isomer
Type
Research Article
Information
Journal of Dairy Research , Volume 75 , Issue 3 , August 2008 , pp. 354 - 356
Copyright
Copyright © Proprietors of Journal of Dairy Research 2008

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Christie, WW 1993 Preparation of ester derivatives of fatty acids for chromatographic analysis. In: Advances in lipid methodology – two (Ed. Christie, WW), Oily Press, Dundee, UK, pp. 69–111Google Scholar
Gunstone, F 1999 Practical applications of oils and fats. In: Fatty acid and lipid chemistry (Ed. Gunstone, F), Aspen Publishers, Maryland, USA, pp. 229–232Google Scholar
Kramer, JKG & Zhou, J 2001 Conjugated linoleic acid and octadecenoic acids: Extraction and isolation of lipids. European Journal of Lipid Science and Technology 103 600–6093.0.CO;2-7>CrossRefGoogle Scholar
Lee, MRF, Tweed, JKS, Moloney, AP & Scollan, ND 2005 The effects of fish oil supplementation on rumen metabolism and the biohydrogenation of unsaturated fatty acids in beef steers given diets containing sunflower oil. Animal Science 80 361–367CrossRefGoogle Scholar
Nuernberg, K, Dannenberger, D, Ender, K & Nuernberg, G 2007 Comparison of different methylation methods for the analysis of conjugated linoleic acid isomers by silver ion HPLC in beef lipids. Journal of Agriculture and Food Chemistry 55 598–602CrossRefGoogle ScholarPubMed
Payne, RW, Murray, DA, Harding, SA, Baird, DB & Soutar, DM 2002 Genstat® for WindowsTM (8th Edition) Introduction. Oxford: VSN InternationalGoogle Scholar
Sukhija, PS & Palmquist, DL 1988 Rapid method for the determination of total fatty acid content and composition of feedstuff and feces. Journal of Agriculture and Food Chemistry 36 1202–1206CrossRefGoogle Scholar