CHEMICAL CHANGES OF PUMPKIN SEED OILS AND THE IMPACT ON LIPID STABILITY DURING THERMAL TREATMENT: STUDY BY FTIR - SPECTROSCOPY

Abstract

Oxidative stability and fatty acid composition of the pumpkin seed oil (PSO) were studied, during roasting process from 80 to 150 °C and oil heat treatment (220 ˚C), by FTIR (Fourier - transform infrared) – Spectroscopy and GC/MS (Gas chromatography - mass spectrometry). The physicochemical parameters (density and iodine value) showed a significant increase (p < 0.05) during roasting, with a maximum value observed in the oil roasted at temperatures from 90 to 110 ˚C. The relative contents of polyunsaturated fatty acids (PUFAs) decreased to 87.7%, and saturated fatty acids (SFAs) increased to 112.5% at unroasted sample, after thermal treatment of oil samples. Especially at temperature 90 and 110 ˚C, oil samples have demonstrated that relative contents of PUFAs decreased to 95 % and SFAs increased to 101.6%. FTIR Spectroscopy provide to understand mechanism of chemical changes of seed during roasting process and, as result, which of obtained compounds are responsible for increasing thermal stability of oil lipids.  In this study, it was observed that the best temperature for roasting pumpkin seeds is 110 ˚C, since at this point, both oxidation and Maillard reactions give rise to compounds with maximum antioxidant effect (lipid stability).