Abstract

Vegetable oils, including pumpkin seed oil (PSO), contained triacylglycerols and some minor components including phenolics and tocopherols which are believed to contribute to antioxidant activities. The objective of this research was (1) to determine the antioxidant activities of PSOs from different origins using 2,2′-diphenyl-1-picrylhydrazil (DPPH) radical scavenging, (2) to classify PSOs from different origins using principal component analysis (PCA) and cluster analysis (CA), and (3) to predict the antiradical activities of PSO based on Fourier transform infrared (FTIR) spectra using multivariate calibration of partial least square regression (PLSR). The antioxidant activities of PSOs were evaluated based on the capability of PSOs to reduce the absorbance values of DPPH. Classification of PSOs from different origins was evaluated using PCA and CA using variables of absorbance values of FTIR spectra, while prediction of antiradical activities using FTIR spectra was facilitated by PLSR. The results showed that radical scavenging activity (RSA) of PSO from Gunung Kidul and Tawangmangu had the highest RSA accounting for 98.71% ± 0.02% and 83.57% ± 0.13%, respectively. PCA could classify PSO from different origins using the variable of FTIR spectra absorbances based on PC1 and PC2 score plots. CA using the same variables could group PSO samples into five groups based on the dendrogram obtained. PLSR using the first derivative FTIR spectra at 3,500–650 cm−1 could predict RSA of PSO with R2 values of 0.9996 and 0.9418 in calibration and validation models, while the root mean square error of calibration and the root mean square error of prediction were of 0.425% and 4.93%, respectively. It can be concluded that FTIR spectra combined with chemometrics are effective means for the classification of PSO from different origins and for the prediction of antioxidant activities of PSO with accurate and precise results.

Key words: antiradical scavenging activities, pumpkin seed oil, chemometrics, FTIR spectra, geographical origin