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.

Comparative analysis of selected bioactive components (fatty acids, tocopherols, xanthophyll, lycopene, phenols) and basic nutrients in raw and thermally processed camelina, sunflower, and flax seeds (Camelina sativa L. Crantz, Helianthus L., and Linum L.)

“…Investigations have indicated greater activity and efficiency of tocopherols occurring naturally in the raw material than those added to the product. Interesting research results were obtained by Hoed et al (2017), who roasted pumpkin seeds at a temperature of 60 to 150 °C and did not observe a downward trend in the content of tocopherols with the increasing temperature of the process.…”

Seed Lipid Composition of New Hybrids of Styrian Oil Pumpkin Grown in Poland

“…Pumpkin seed oil is relatively oxidatively stable because it contains minor or trace amounts of linolenic acid. The positive effect of γ-tocopherol was expected because of the highest antioxidative properties of this tocopherol homolog [65].…”

Sagittaria trifolia tuber: bioconstituents, processing, products, and health benefits

“…101 Heat-mediated increase in phenols is a universal phenomenon, which has been reported in the roasted sprouts of barley and wheat, 102 large-leaf yellow tea, 103 seeds of Bauhinia petersiana, 104 and pumpkin seed oil. 105 The increased phenols after roasting could be related to the fact that thermal processing accelerates the breakdown of cellular constituents to facilitate the release of bound biocomponents. 106 Existing research findings about S. trifolia tuber processing are still limited.…”