Detection of olive oil adulteration by corn oil addition applying ATR-FTIR spectroscopy

Mariana-Atena Poiana, George A. Mousdis, Constantinos A. Georgiou

Volume 19, Issue 2;
Pages: 141-147;
ISSN: 2069-0053 (print) (former ISSN: 1453-1399), Agroprint;
ISSN (online): 2068-9551
The main objective of this study was to assess the potential of Attenuated Total Reflectance - Fourier Transform Infrared (ATR-FTIR) spectroscopy for detection of olive oil (OO) adulteration by corn oil (CO) addition. The differences recorded for the band around 3006 cm−1 assigned to the C–H stretching vibration of the cis-double bonds (=CH) can be used for quantification of OO adulteration. The height of the 3006 cm−1 band for pure OO sample is obviously smaller than for pure CO or for its mixtures with OO. The maximum absorbance value of the band at this frequency changed according to the extent of OO adulteration. Also, the position of this band has shifted versus the percentage of CO added in OO from 3009 to 3005 cm−1. The maximum heights of the two bands at ~3006 and 2922 cm−1 were also used in assessing of OO adulteration. The 2922 cm−1 band is assigned to the symmetric stretching vibration of the aliphatic –CH2 groups. The calculated ratio of the two peak heights express the percentage of the hydrogen–carbon bonds linked by cis-double bonds (=CH) present in the oil samples. There was recorded a high correlation (R2=0.91) between the ratio of these peak heights and the percentage of CO added to OO. Based on calibration curve absorbance versus the percentage of adulterant in OO it is possible to assess the OO samples’ adulteration. Significant positive correlations (R2>0.94) were found at some specific frequencies i.e. 3011, 3006 and 722 cm-1, respectively, while for 1096 and 912 cm-1 it was recorded R2 values of 0.9. The combined frequency regions 3020–3000, 1100–900, 750–700 could be successfully used for quantification the OO counterfeit by CO addition as a possible adulterant agent. Based on our results it can be noticed that ATR-FTIR spectroscopy could be successfully used as a rapid, non-destructive technique with a minimum sample preparation for detection of OO adulteration.
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