Analytical Sciences

Automated and Simultaneous Determination of Free Fatty Acids and Peroxide Values in Edible Oils by FTIR Spectroscopy Using Spectral Reconstitution

Xiuzhu YU,* Shuangkui DU,* Frederick R. van de VOORT,** Tianli YUE,* and Zhixi LI*

*College of Food Science and Engineering, Northwest A & F University, Yangling, Shaanxi 712100, P. R. China
**Department of Food Science and Agricultural Chemistry, McGill University, Sainte-Anne-de-Bellevue, Québec H9X 3V9, Canada

This paper described an FTIR spectrometer coupled to an auto-sampler and some attendant methodologies for a direct free fatty acid (FFA) method and triphenylphosphine (TPP)-based method for determination of FFA and peroxide value (PV) of edible oils by FTIR spectroscopy using spectral reconstitution. The viscosity of oil samples is reduced by mixing them with a diluent; such lowered viscosity allows them to be readily loaded into a flow-through transmission cell. The spectra of the neat oil samples are then reconstituted from those of the diluted samples by using the absorption of a spectral marker present in the diluent to determine the dilution ratio. For the direct FFA analysis, quantification is achieved using the (COO^-) band at 1712 cm^-1, while PV is determined using triphenylphosphine oxide (TPPO) absorption bands at 542 cm^-1. Calibration procedures and data are presented. Validation and performance data obtained with this automated system demonstrate that it is capable of analyzing ∼90 samples/h, a rate commensurate with the throughput required by commercial contract or high-volume process control laboratories.

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