ABSTRACT: A Fourier transform infrared (FTIR) edible oil analysis package designed to simultaneously analyze for trans content, cis content, iodine value (IV), and saponification num- ber (SN) of neat fats and oils by using calibrations based on pure triglycerides and derived by application of partial-least-squares (PLS) regression was assessed and validated. More than 100 hy- drogenated rapeseed and soybean samples were analyzed by using the edible oil analysis package as well as the newly pro- posed modification of the AOCS IR trans method with trielaidin in a trans-free oil as a basis for calibration. In addition, ~1/3 of the samples were subsequently reanalyzed by gas chromatogra- phy (GC) for IV and trans content. The PLS approach predicted somewhat higher trans values than the modified AOCS IR method, which was traced to a combination of the inclusion of trilinolelaidin in the calibration set and the effects of baseline fluctuations. Eliminating trilinolelaidin from the triglyceride standards and the use of second-derivative spectra to remove baseline fluctuations produced excellent concurrence between the PLS and modified AOCS IR methods (mean difference of 0.61% trans). Excellent internal consistency was obtained be- tween the IV and cis and trans data provided by the edible oil analysis package, and the relationship was close to that theoret- ically expected [IV = 0.86 (cis + trans)]. The IV data calculated for the GC-analyzed samples matched the PLS IV predictions within 1 IV unit. The trans results obtained by both IR methods were linearly related to the GC data; however, as is commonly observed, the GC values were significantly lower than the IR values, the GC and IR data being related by a slope factor of ~0.88, with an SD of ~0.80. The concurrence between the trans data obtained by the two FTIR methods, and between the FTIR and GC–IV data, as well as the internal consistency of the IV, cis and trans FTIR predictions, provides strong experimental ev- idence that the edible oil analytical package measures all three variables accurately. JAOCS 75, 33–39 (1998). KEY WORDS: Cis, FTIR spectroscopy, fats and oils, Fourier transform infrared spectroscopy, iodine value (IV), lipid analy- sis, oil analysis, trans, trans analysis, triglycerides. Edible fats and oils vary in their triglyceride makeup, relative degree and forms of unsaturation (cis or trans), weight-aver- age molecular weight, and overall fatty acid composition/dis- tribution, and these complex determinants define the physico- chemical properties of the lipid system. For stability and func- tionality reasons, oils are often hydrogenated and converted into fats. Hydrogenation reduces the overall degree of unsat- uration, but also leads to increased levels of trans fatty acids, now of increasing concern to health professionals due to their association with heart disease (1). Trans fatty acid levels can reach values of 40% or more in hardened fats, and considera- tion is being given to legislation to require the labeling of the trans content in fat-based products, such as margarines, spreads and frying fats (2). For oil processors, iodine value (IV) and trans content are important process parameters, which require monitoring during hydrogenation to ensure that consistent products with desired physical properties are pro- duced. As such, the availability of a simple, rapid and routine means of determining IV and trans directly on neat fats and oils would be of substantial benefit. The McGill FTIR Group has been carrying out research on the development of simple, rapid, and accurate methods of edible oil analysis, based on Fourier transform infrared (FTIR) spectroscopy (3–10). One of the practical develop- ments of this research has been an FTIR-based edible oil analysis package, which is capable of simultaneously deter- mining IV, saponification number, and cis and trans content (IV/SN/cis/trans) in a single analysis on a neat fat or oil in less than 2 min. The system is preprogrammed and precali- brated and has a heated sample accessory (8) to allow both fats and oils to be analyzed in their liquid state at 80°C; a commercial version is marketed by Nicolet Instrument (Madi- son, WI). This system is in use by a number of edible oil processors who are satisfied with its performance; however, it has been noted, through our own as well as the users’ experi- ence with the system, that, although the trans and IV predic- tions are linearly related to their own reference analyses, the trans values tend to be overestimated. This is readily cor- rected for by linear regression; however, because the original concept for the development of the method is to be indepen- dent of recalibrations or adjustment, we felt that this problem should be addressed by a structured validation study. This study, carried out in cooperation with a major European edi- Copyright © 1998 by AOCS Press 33 JAOCS, Vol. 75, no. 1 (1998) *To whom correspondence should be addressed. E-mail: af55@musica.Mcgill.ca. 1 Co-Director, McGill IR Group. 2 n.v. Vandemoortele Coordination Center, Group R&D Center, Prins Albert- laan 79, P.O. Box 40, B-8870 Izegem (Belgium). Industrial Validation of Fourier Transform Infrared trans and Iodine Value Analyses of Fats And Oils J. Sedman, F.R. van de Voort,* A.A. Ismail 1 , and P. Maes 2 McGill IR Group, Department of Food Science and Agricultural Chemistry, Macdonald Campus of McGill University, Ste. Anne de Bellevue, PQ, H9X 3V9 Canada