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 (EC(50)) of 27.18 mg oil/mg DPPH.