Changes in chemical composition of pumpkin seeds during the roasting process for production of pumpkin seed oil (Part 1: non-volatile compounds)

Pumpkin seed oil is a common salad oil in Austria. It is not only of interest because of its typical taste but also because of its potential in curing prostate disease. Besides the fatty acids, the micronutrients, which comprise vitamin E, phytosterols and lignans, are of special interest. Since the seeds are roasted before pressing of the oil, changes occur in the composition of the fatty acids and micronutrients. The oxidation-sensitive linoleic acid decreases from 54.6 to 54.2% whereas the concentrations of the vitamin E isomers show a decrease during the first 40 min of about 30% followed by an increase during the last 20 min to about the same level as at the beginning of the roasting process. The concentrations of α-tocopherol and γ-tocopherol in the fresh dried seeds are 37.5 and 383 μg/g, respectively. The concentration of the tocotrienols is about one third of the corresponding tocopherols. The initial concentration of the total sterols (1710 μg/g) increases to 1930 μg/g. The increases of the sterols and vitamin E during the roasting process could be attributed to the changes of the seed meal, since at the end of the roasting the oil emerges from the seeds resulting in altered chemical behaviour of the extraction process. Secoisolariciresinol, which is only detectable at the beginning with a concentration of 3.8 μg/g, is destroyed after 20 min.