Abstract
Objective: The study was designed to develop Fourier transform infrared (FTIR) spectroscopy in conjunction with chemometrics techniques of multivariate calibration and discriminant analysis (DA) for analysis of palm oil in a ternary mixture with EVOO and PSO.
 Methods: FTIR spectra of pure palm oil (PO), extra virgin olive oil (EVOO), pumpkin seed oil (PSO) and its ternary mixtures randomly prepared were scanned using FTIR spectrophotometer at wavenumbers of 4000-650 cm-1 corresponding to mid-infrared region, with resolution of 8 cm-1 and 32 scanning using sampling technique of attenuated total reflectance (ATR). Two calibrations in multivariate models, namely principle component (PCR) and partial least square (PLS) regressions were used to facilitate quantification of PO.
 Results: The PLS using first derivative FTIR–ATR spectra at 3100-2750 combined with 1500-663 cm-1 showed the best prediction models for quantification of PO in ternary mixtures with EVOO and PSO. Using this condition, correlation coefficient (R) values for the relationship between actual values and FTIR predicted values of 0.9967 and 0.9906 were achieved in calibration and validation models, respectively. The errors in calibration and prediction models, expressed by RMSEC and RMSEP, were low, i.e. 0.0080% and 0.0152%, respectively. DA using absorbance values at the same wavenumbers also offered the optimum discrimination model for discrimination between PO and PO mixed with EVOO and PSO in ternary mixtures.
 Conclusion: This result concluded that FTIR spectra in conjunction with DA (for classification) and PLS (for quantification) is fast and accurate tools during the analysis of PO as oil adulterant in EVOO and PSO.
Highlights
Known as the highest olive oils, extra-virgin olive oil (EVOO) command high priced vegetable oil because extra virgin olive oil (EVOO) is only obtained by means of the physical and mechanical processes of fresh and healthy fruits of olive (Olea europaea) in the appropriate maturation stage without any treatments which cause its original composition changed [1, 2]
All fatty acid (FA) in palm oil (PO) and EVOO were in agreement with those specified in Codex Allimentarius Commission, while FAs in pumpkin seed oil (PSO) in this study was in accordance with those reported in the literature [24]
These FAs data indicated that studied oils (PO, EVOO and PSO) were not previously mixed with other oils
Summary
Known as the highest olive oils, extra-virgin olive oil (EVOO) command high priced vegetable oil because EVOO is only obtained by means of the physical and mechanical processes of fresh and healthy fruits of olive (Olea europaea) in the appropriate maturation stage without any treatments which cause its original composition changed [1, 2]. EVOO is taken into accound as high-quality edible oil due to its nutritional benefits; the appreciated features, pleasant taste, and enjoyable flavor [3, 4]. EVOO is reported in inhibiting some disease risk factors, such as diabetes, metabolic syndrome and obesity [6] and preventing certain cancers, especially breast and digestive tract cancers [7]. Pumpkin seed oil (PSO) is considered as one of the functional edible oils [9]. PSO contained high levels of vitamin E, carotenoids and unsaturated fatty acids, contributing to beneficial effects on human health in prevention of high cholesterol levels, prostate cancer, and molacular degeneration [10, 11]. PSO may be adulterated with cheaper seed oil like palm oil [12]
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