INDUSTRIAL VALIDATION OF FOURIER-TRANSFORM INFRARED TRANS AND IODINE VALUE ANALYSES OF FATS AND OILS

A Fourier transform infrared (FTIR) edible oil analysis package design ed to simultaneously analyze for trans content, cis content, iodine va lue (IV), and saponification number (SN) of near fats and oils by usin g calibrations based on pure triglycerides and derived by application of partial-least-squares (PLS) regression was assessed and validated. More than 100 hydrogenated rapeseed and soybean samples were analyzed by using the edible oil analysis package as well as the newly proposed modification of the AOCS IR trans method with trielaidin in a trans-f ree oil as a basis for calibration. In addition, similar to 1/3 of the samples were subsequently reanalyzed by gas chromatography (GC) for I V and trans content. The PLS approach predicted somewhat higher trans values than the modified AOCS IR method, which was traced to a combina tion of the inclusion of trilinolelaidin in the calibration set and th e effects of baseline fluctuations. Eliminating trilinolelaidin from t he triglyceride standards and the use of second-derivative spectra to remove baseline fluctuations produced excellent concurrence between th e PLS and modified AOCS IR methods (mean difference of 0.61% trans). E xcellent internal consistency was obtained between the IV and cis and trans data provided by the edible oil analysis package, and the relati onship was close to that theoretically expected [IV = 0.86 (cis + tran s)]. The IV data calculated for the GC-analyzed samples matched the PL S IV predictions within 1 IV unit. The trans results obtained by both IR methods were linearly related to the GC data; however, as is common ly observed, the GC values were significantly lower than the IR values , the GC and IR data being related by a slope factor of similar to 0.8 8, with an SD of similar to 0.80. The concurrence between the trans da ta obtained by the two FTIR methods, and between the FTIR and GC-IV da ta, as well as the internal consistency of the IV, cis and trans FTIR predictions, provides strong experimental evidence that the edible oil analytical package measures all three variables accurately.