The use of FTIR spectroscopy in combination with chemometrics for the authentication of red fruit (Pandanus conoideus Lam) oil from sunflower and palm oils

Abstract

In this study, Fourier transform infrared (FTIR) spectroscopy in combination with multivariate calibration based on partial least squares (PLS) has been developed for quantitative analysis of sunflower oil (SFO) and palm oil (PO) as oil adulterants in red fruit oil (RFO) for the authentication study. The binary mixtures of SFO and PO in RFO were infrared spectroscopically scanned using horizontal attenuated total reflectance at mid infrared region (4000-650 cm-1). Some frequency regions where the variations were observed among RFO, SFO, and PO were optimized in order to seek the best frequency regions giving the best PLS calibration models. Besides, the derivatization of FTIR spectra (fisrt and second derivatives) was also investigated in order to look the types of FTIR spectra giving the best spectral performance in the model. The results showed that SFO was better determined using FTIR normal spectra at the frequency region of 1200-1000 cm-1 with coefficient of determination (R2) of >0.99 and with root mean square error of calibration (RMSEC) of 1.42% v/v. FTIR normal spectra were also more preferred than its derivative for the quantification of PO in RFO. The R2 value obtained for the relationship between actual value (reference value) and predicted value obtained during PLS modeling is very high (0.9991) with the low level of error (RMSEC of 0.98% v/v). It can be concluded that FTIR in combination with PLS is a reliable method for quantitative analysis of SFO and PO as adulterant in RFO for authenticity verification.