Influence of seed roasting on pumpkin seed oil tocopherols, phenolics and antiradical activity

To achieve the aroma and colour typical of pumpkin seed oil, production includes a roasting step, in which pressed pumpkin seeds are exposed to temperatures of 110 degrees C and above for up to 60 min. Our purpose was to investigate the effect of roasting temperature on pumpkin seed oil tocopherols and phenolics as important compounds for its nutritional value. In this study, pumpkin seeds of two varieties were roasted at temperatures from 90 to 200 degrees C, with one sample left unroasted for comparison purposes. Concentrations of alpha- and gamma-tocopherol and phenolic compounds, as well as antiradical activity, were determined. Among the polyphenols, vanillic, caffeic, transcinnamic and p-coumaric acid were detected. The highest observed concentrations of these polyphenolic acids were 3.08, 0.42, 2.48 and 1.91 mg/kg, respectively. As roasting temperatures increased, polyphenol concentrations decreased. The least significant changes were observed in alpha- and gamma-tocopherols, with concentrations ranging from 51 to 113 mg/kg and 356 to 646 mg/kg, respectively. Antiradical activity was determined spectrophotometrically via 2,2-diphenyl-1-picrylhydrazyl (DPPH) testing. The antiradical effect values ranged from 31.4 to 70.6% and 19.3 to 47.7% for Gleisdorf and Rustikal samples, respectively. Several chemical parameters (acid, saponification, peroxide and iodine values) were also examined.