Authentication of cod liver oil from selected edible oils using FTIR spectrophotometry and chemometrics
2017
Rohman, A. | Widyaningtyas, R. | Amalia, F.
Cod liver oil (CLO) is one of the expensive oils in the market. This attracted unethical players in fats and oils industry to adulterate CLO with selected oils. This study is intended to authenticate CLO from sunflower, corn, and grape seed oils using FTIR spectroscopy in combination with chemometrics. FTIR spectra of CLO, sunflower oil (SFO), corn oil (CO), grape seed oil (GSO), and their binary mixtures were measured in mid infrared region (4,000 – 650 cm-¹) using 32 scanning with resolution of 4 cm-¹. Quantitative analysis of CLO in binary mixtures with SFO, CO, and GSO was assisted with multivariate calibration of partial least square (PLS). The selection of SFO, CO and GSO as oil adulterants was based on the close similarity of these oils to CLO in terms of FTIR spectra, as analyzed using principal component analysis. CLO in GSO is determined using normal spectra at wavenumbers region of 1250 – 950 cm-¹. The equation for the correlation between actual value of CLO (x-axis) and FTIR predicted value (y-axis) is y = 0.9938x + 0.1567 with R2 value of 0.9962. PLS using normal spectra at wavenumbers of 1350-900 cm-¹ is preferred for the quantification of CLO in binary mixture with CO with coefficient of determination (R² ) value of > 0.9999 and root mean square error of calibration (RMSEC) value of 0.48% (v/v). The wavenumbers of 1350-900 cm-¹ along with FTIR normal spectra are suitable for quantification of CLO in binary mixture with GSO. Based on the high value of R² and low values of errors, it can be concluded that FTIR spectroscopy coupled with chemometrics can be used for analysis of CLO adulterated with sunflower, corn, and grape seed oil.
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