Trans determination of edible oils by Fourier transform near-infrared spectroscopy

A generalized partial-least-squares calibration for determination of the tr ans content of edible fats and oils by Fourier transform near-infrared (FT- NIR) spectroscopy using 8-mm disposable glass vials for sample handling and measurement was developed. The trans contents of a broad range of oils wer e determined using the American Oil Chemists' Society single-bounce horizon tal attenuated total reflectance (SB-HATR) mid-infrared spectroscopic proce dure, these trans reference data were used in the development of the genera lized FT-NIR calibration. Additional refined and product-specific calibrati ons were also developed, and all the calibrations were assessed for their p redictive capabilities using two sets of validation samples, one comprising a broad range of oil types and the other restricted to oils with specific characteristics. The FT-NIR trans predictions obtained using the generalize d calibration were in good agreement with the SB-HATR results; the values w ere accurate and reproducible to within +/-1.1 and +/-0.5% trans, respectiv ely, compared to a reproducibility of +/-0.40% trans obtained for the SB-HA TR method. The accuracy of the predictions obtained from the generalized FT -NIR calibration for particular oil types was not significantly improved by supplementing the base training set with samples of these specific types. Calibrating only these oil types did, however, produce a substantial improv ement in predictive accuracy, approaching that of the SB-HATR method. These product specific calibrations produced serious predictive errors when nonr epresentative samples were analyzed. The incorporation of a supplementary d iscriminate analysis routine was found to be a powerful safeguard in flaggi ng nonrepresentative samples as outliers and could also be used to select t he calibration most appropriate for the characteristics of the sample being analyzed. Overall, it was concluded that FT-NIR spectroscopy provides a vi able alternative to the SB-HATR/mid-Fourier transform infrared method for t rans determination, making use of more industrially robust instrumentation and equipped with a simpler sample handling system.