Changes in chemical composition of pumpkin seeds during the roasting process for production of pumpkin seed oil (Part 2: volatile compounds)

Pumpkin (Cucurbita pepo L.) seed oil is a special product of the southern Austrian region. For the production of the oil, prior to the pressing procedure, the seeds are roasted at temperatures up to 130 °C, which leads to the formation of the typical roasty and nutty aroma. In this study, changes of composition of the volatile fraction of the pumpkin seeds in course of the roasting process are investigated. The analyses were performed by gas chromatography–mass spectrometry after headspace solid phase microextraction. The results show very clearly that the roasting process at these high temperatures is necessary to obtain the typical aroma of the pumpkin seed oil. Compounds that are responsible for roasty/nutty aroma notes (alkylated pyrazines, as well as 2-acetylpyrrole) require a roasting temperature of at least 90 °C. Other compounds that show significant changes in concentration are mainly Strecker degradation products, as well as compounds derived from lipid oxidation.