Rapid determination of peroxide value in crude palm oil products using Fourier transform infrared spectroscopy.

摘要

Hydroperoxide contents in oils are traditionally determined by peroxide values (PV) using labour intensive chemical methods that use large quantities of acidified solvent. Fourier transform infrared (FTIR) spectroscopy has potential for quantitative analysis of fats and oils, and has been used recently to determine iodine values, saponification number and free fatty acid and carotene contents in fats and oils. In this study, an FTIR method coupled with fixed NaCl cell (1 mm pathlength) was developed to measure PV in crude palm oil (CPO) and crude palm kernel oil (CPKO). Calibration standards were prepared by oxidizing CPO in a fermentor at 60 degree C for 24 h. A partial least squares (PLS) calibration model for predicting PV was developed based on the 3710-3210 cm---1 spectral region with reference to a single-point baseline at 3710 cm---1. Optimization of calibration factors was guided by the predicted residual error sum of squares (PRESS) test. The s.d. of the calibration was 0.46 PV over the PV range 0.51-17.982; correlation coeff. (R-2) was 0.998. The model was validated using an independent set of samples consisting of both laboratory and field samples. The overall s.d for the validation set was slightly higher (s.d. = 1.46 PV) with R-2 of 0.989. PV measured by FTIR spectroscopy were comparable to those obtained by the chemical method. It is concluded that FTIR spectroscopy with a fixed NaCl cell offers a viable method for measuring PV in CPO and CPKO and a simple way of handling palm oil. In addition, the method is rapid (less than or equal 2 min) and requires only min. quantities of organic solvent.