Abstract:

This study aimed to develop a rapid method for the detection of carbonyl value (CV) in edible oils. Anisaldehyde
was used as carbonyl reference and gravimetrically added to carbonyl-free rapeseed oil. A series of CV (0–60 mmol/kg)
oil samples were determined using polyethylene (PE) film as a spectrum acquisition accessory. A linear relationship between
CV and absorbance at the characteristic absorption peak (1 703/1 570 cm-1, peak at 1 703 cm-1 and two base points at
1 570 cm-1) was established. However, different types of edible oils exhibited substrate effect, which showed that 1 703 cm-1
had variability even among their carbonyl-free samples. To correct the substrate effect, peak absorption at 3 472 cm-1,
as evaluated by the 2-D correlation spectroscopy technique, was used as the relevant absorption peak to 1 703 cm-1.
Subsequently, a liner relationship between both peak heights was established. Results indicated that there was a highly linear
correlation between CV and the absorbance at 1 703 cm-1. The corrected model was y = 0.005 4 x + 0.090 9. with a correlation
coefficient (R) of 0.991 9 and standard deviation of 0.013 mmol/kg. Moreover, there was a good relationship between the values
obtained from the national standard method and the corrected model, with a slope close to 1, and correlation coefficient of more
than 0.99. Thus the PE film-based FTIR method for determination CV in edible oils is workable.

Key words: edible oils, Fourier transform infrared spectroscopy (FTIR), carbonyl value, determination