Determining CLA Isomers in Soy Oil

December 9/Food Weekly Focus -- According to recent research from the U.S., "Conjugated linoleic acid (CLA) isomers in oils are currently measured as fatty acid methyl esters by a gas chromatography-flame Ionization detector (GC-FID) technique, which requires approximately two hours to complete the analysis. Hence, we aim to develop a method to rapidly determine CLA isomers in CLA-rich soy oil."

"Soy oil with 0.38-25.11% total CLA was obtained by photo-isomerization of 96 soy oil samples for 24 hours. A sample was withdrawn at 30-minute intervals with repeated processing using a second batch of oil. Six replicates of GC-FID fatty acid analysis were conducted for each oil sample. The oil samples were scanned using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and the spectrum was collected. Calibration models were developed using partial least-squares (PLS-1) regression using Unscrambler software. Models were validated using a full cross-validation technique and tested using samples that were not included in the calibration sample set. Measured and predicted total CLA, trans,trans CLA isomers, total mono trans CLA isomers, trans-10,cis-12 CLA, trans-9,cis-11 CLA and cis-10,trans-12 CLA, and cis-9,trans-11 CLA had cross-validated coefficients of determinations (R-v(2)) of 0.97, 0.98, 0.97, 0.98, 0.97, and 0.99 and corresponding root-mean-square error of validation (RMSEV) of 1.14, 0.69, 0,27, 0.07, 0.14, and 0.07% CLA, respectively," wrote J.V. Kadamne and colleagues, University of Arkansas.

The researchers concluded, "The ATR-FTIR technique is a rapid and less expensive method for determining CLA isomers in linoleic acid photo-isomerized soy oil than GC-FID."

Kadamne and colleagues published their study in the Journal of Agricultural and Food Chemistry ("Measurement of Conjugated Linoleic Acid (CLA) in CLA-Rich Soy Oil by Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR)." Journal of Agricultural and Food Chemistry, 2009;57(22):10483-10488).

For additional information, contact A. Proctor, University of Arkansas, Dept. of Food Science, 2650 N Young Avenue, Fayetteville, AR 72704.

From the December 21, 2009, Prepared Foods E-dition