Oxidation stability and compositional characteristics of oils from microwave roasted pumpkin seeds during thermal oxidation

The oxidative stability and compositional characteristics of the pumpkin seed oil (PSO) exposed to microwaves were studied during heating at 170°C. The oxidative indices such as free fatty acid (FFA), peroxide value (PV), p-anisidine value (p-AV), TOTOX, specific extinctions and thiobarbituric acid (TBA) value of oils were significantly increased, and the increments were found to be significantly higher (P < 0.05) in unroasted seed oil as compared to roasted seed oil. The relative contents of polyunsaturated fatty acids (PUFAs) were decreased to 84.7%, and saturated fatty acids (SFAs) were increased to 119.5% in unroasted sample, after 9 h of heating. On the other hand, in 12 min roasted samples, the relative contents of PUFAs were decreased to 97.0%, and SFAs were increased to 102.6% after 9 h of heating. The triacylglycerol species LLL and OLL levels were decreased as a consequence of increased heating time, and the reduction tended to be significantly higher in unroasted samples as compared to roasted ones. The oxidation products formed were also investigated by FTIR. The present results indicated that microwave roasting of pumpkin seeds markedly enhanced the oxidative stability of the oils during heating.