Optimization of Hull‐Less Pumpkin Seed Roasting Conditions Using Response Surface Methodology

Abstract: Response surface methodology (RSM) was applied to optimize hull‐less pumpkin seed roasting conditions before seed pressing to maximize the biochemical composition and antioxidant capacity of the virgin pumpkin oils obtained using a hydraulic press. Hull‐less pumpkin seeds were roasted for various lengths of time (30 to 70 min) at various roasting temperatures (90 to 130 °C), resulting in 9 different oil samples, while the responses were phospholipids content, total phenols content, α‐ and γ‐tocopherols, and antioxidative activity by 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) free‐radical assay]. Mathematical models have shown that roasting conditions influenced all dependent variables at P < 0.05. The higher roasting temperatures had a significant effect (P < 0.05) on phospholipids, phenols, and α‐tocopherols contents, while longer roasting time had a significant effect (P < 0.05) on γ‐tocopherol content and antioxidant capacity, among the samples prepared under different roasting conditions. The optimum conditions for roasting the hull‐less pumpkin seeds were 120 °C for duration of 49 min, which resulted in these oil concentrations: phospholipids 0.29%, total phenols 23.06 mg/kg, α‐tocopherol 5.74 mg/100 g, γ‐tocopherol 24.41 mg/100 g, and an antioxidative activity (EC₅₀) of 27.18 mg oil/mg DPPH. Practical Application: A well‐defined roasting process is very important for the food industry to be able to produce pumpkin seed oil with desirable nutritive and chemical characteristics of this unique salad oil, which changes during the roasting. This study contributes to the knowledge of a product design process for the roasting conditions of naked pumpkin seeds based on results that have demonstrated that an increase in roasting temperature significantly increased the biochemical values and antioxidant properties of the obtained virgin oils.