Effect of seed pretreatment, screw speed, and pressing conditions on yield, quality, and fatty acid distribution of pumpkin seed oil

This study investigated the combined effects of seed pretreatment, pressing type (PT), and screw speed (SP) on the physicochemical quality and fatty acid distribution of pumpkin seed oil (PSO) extracted from Cucurbita pepo seeds. A completely randomized design (3 × 3 × 2) was employed, with seed pretreatment (whole, roasted, dehulled), SS1=30, SS2=40, SS3=50 rpm), and pressing type (hot, cold) as experimental factors. Oil yield, physicochemical parameters (pH, refractive index, viscosity, specific gravity, moisture content, saponification, iodine, peroxide, titratable acidity, acid value, smoke point), and fatty acid composition were analyzed using standard AOAC methods and GC–MS. Results showed that all factors significantly (p < 0.05) influenced oil yield and quality. Hot pressing produced the highest yield (47.87%) but increased acidity and reduced oleic acid content due to thermal degradation. Cold pressing preserved better nutritional quality, exhibiting higher oleic acid (up to 19.32%) and lower peroxide and acid values. Dehulling improved saponification value, and smoke point (up to 212 °C), while roasting improved flavor potential but reduced oxidative stability. Linoleic acid (C18:2) was the predominant fatty acid (56.08–59.43%), followed by oleic (C18:1), palmitic (C16:0), and stearic (C18:0) acids. Optimal quality was achieved from cold-pressed dehulled seeds at 40 rpm, balancing yield and unsaturation retention. The findings demonstrate that SP and SS are critical in tailoring PSO for functional food and nutraceutical applications, providing a basis for process optimization in sustainable oil production.