Tocopherols and Polyphenols in Pumpkin Seed Oil Are Moderately Affected by Industrially Relevant Roasting Conditions

Abstract

Traditionally, pumpkin seed oil is obtained by pressing the seeds after a roasting pretreatment, at temperatures up to 150 °C. However, the appropriate temperatures and roasting times are under discussion. In this study, oils from seeds roasted at different temperatures (60–150 °C) are compared with oil from non‐roasted seeds. At higher roasting temperatures, lower roasting times are required to release the oil. Both, for tocopherols and phenolic compounds, no decreasing trend with the increasing roasting temperature are observed. In contrast, the oil from non‐roasted seeds have relatively low levels of tocopherols and phenolics and lacked the typical aroma. Levels of polyaromatic hydrocarbons (PAHs) are very low, ranging from not detected in oil from non‐roasted seeds to 13.8 μg kg−1 in the oil from seeds roasted at 150 °C. Therefore, the choice between the studied roasting conditions may depend rather on sensory evaluations than on the content of antioxidants or of PAHs. Practical Applications: The process of the production of virgin pumpkin oil is based on a thermal treatment of the ground seeds, favoring the separation of the lipid fraction, and giving a typical aroma of the roasted oil. Results of this research provide important information regarding the influence of roasting conditions on the quality and safety of the oil. Roasting pumpkin seeds increased the tocopherol and phenols content in the pumpkin oil, with no significant formation of PAHs. The information will be valuable and important for not only for the pumpkin oil production, but also for all the seeds submitted to a roasting treatment before extraction.Pumpkin seed oil is traditionally produced in several European countries and commonly used in salad dressing. The production of pumpkin seed oil frequently includes roasting of the seeds at high temperatures, which may influence the amount of phenolic compounds and the final nutritional quality of the oil. The roasting of the pumpkin seeds is necessary to obtain the desired color, flavor, and taste characteristics. At higher roasting temperatures, lower roasting times are required to release the oil. Both, for tocopherols and phenolic compounds, no decreasing trend with the increasing roasting temperature is observed.