Abstract
The adulteration practice of high price oils such as pumpkin seed oils (PSO) with lower ones could be motivated by economic gains. The objective of this study was to apply FTIR spectroscopy in combination with chemometrics of multivariate calibrations and discriminant analysis for the authentication of PSO. A total of fifteen oils were scanned using FTIR spectrophotometer at mid-infrared regions (4000-650 cm-1 ) and subjected to principal component analysis (PCA) using absorbance values at whole mid-IR regions to know oil having a close similarity to PSO in terms of FTIR spectra. Two multivariate calibrations namely principle component regression (PCR) and partial least square regression (PLSR) along with FTIR spectra modes (normal, derivative-1, and derivative2) were optimized to get the best prediction models. In addition, discriminant analysis (DA) was used for classification of PSO and PSO adulterated with oil adulterant. The results showed that among 15 oils, sesame oil (SeO) had the closer score plot in terms of the first principle component and second principle components with that of PSO. Based on the statistical parameters selected (higher R2 and lowest errors), FTIR spectra in derivative -1 mode at wavenumbers of 1800-663 cm-1 were selected for quantification of PSO in SeO with coefficient of determination (R) values of 0.9998 and 0.9994 in calibration and validation models, respectively. The values of root mean square error of calibration (RMSEC) and root mean square error of prediction obtained were 0.003% and 0.006%, respectively. DA using 10 principle components could clearly discriminate PSO and PSO adulterated with SeO with accuracy levels of 100%. FTIR spectroscopy in combination with chemometrics could be an effective means to detect the adulteration of PSO with SeO.
Highlights
This study was aimed to develop Fourier transform infrared (FTIR) spectroscopy combined with multivariate calibrations and discriminant analysis for authentication of pumpkin seed oil (PSO) from sesame oil
principal component analysis (PCA) was used to look for oils having similar characteristics to PSO, as depicted as score plot of first principle component analysis (PC1) and second principle component (PC2) using absorbances at whole mid-infrared region (4000-650 cm1) as variables
FTIR spectrum of sesame is similar to that of sesame oil (SeO), SeO was selected as oil adulterant. This indicated that PSO and SeO had a similar FTIR spectrum
Summary
Pumpkin (Cucurbita maxima) belongs to Cucurbitaceae family which widely grows in tropical regions and has a relatively high economic importance around the world. Food industry has exploited to use pumpkin for the production of juices, purees, jams and alcoholic beverages (Jiao et al, 2012). Pumpkin seed refers to the edible seed of a pumpkin, containing some bioactive compounds frequently used as herbal medicines and functional foods. Pumpkin seeds are commonly used in culinary practices mainly in Southeast Asian countries. In Indonesia, pumpkin is one of the popular vegetables consumed as considered as a functional food due to the extraordinary rich sources of bioactive compounds having beneficial health effects (Montesano et al, 2018). Pumpkin seed oil (PSO), a strongly dichromatic viscous oil extracted from pumpkin seed, has gained great attention in fats and oils industry as edible oil and as a potential nutraceutical (Rezig et al, 2012)
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