Determination of the peroxide value of edible oils by FTIR spectroscopy using polyethylene films
Abstract
A new technique was developed to facilitate the mid-FTIR transmission analysis of viscous edible oils using disposable polyethylene (PE) films as a sample support for the determination of the peroxide value (PV) of the oils. The basis of the PV quantification is the rapid reaction of triphenylphosphine (TPP) with lipid hydroperoxides present in an oil to produce triphenylphosphine oxide (TPPO), which has a measurable absorption band at 542 cmā1. Calibration standards, prepared by the gravimetric addition of a peroxide-free oil, were used to develop a linear calibration equation that relates the concentration of TPPO (expressed as the equivalent PV) to the absorption value of TPPO in the normalized spectra. PV determinations on two sets of validation samples, with PV ranges of 2 to 25 and 0 to 2 mmol kgā1 oil, were carried out using both the American Oil Chemists' Society (AOCS) titrimetric method and our PE-based FTIR procedure. A comparison of the results of these analyses indicated that the FTIR method is more reproducible and slightly more sensitive than the conventional method.
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