EFFECT OF ROASTING TEMPERATURE AND EXTRACTION TIME ON THE PHYSICOCHEMICAL PROPERTIES OF PUMPKIN (Cucurbita pepo sp.) SEED OIL

Abstract

Pumpkin seeds, often known as pepitas, are edible, dense with nutrients, and could produce edible oil, but perceived as food waste. This study was intended to determine how roasting temperature and extraction time affected the physicochemical properties of solvent-extracted pumpkin (Cucurbita pepo sp.) seed oil. The experiment was planned with two factors, roasting temperature with three levels (120, 140, and 160oC) and extraction time with three levels (2, 4, and 6 hr). Twelve treatments were implemented in a full factorial design with three replications. Pumpkin seeds were roasted in an electric oven for 15 minutes, while unroasted seeds were used as a control, and solvent extraction was performed using hexane. The results showed that the physical properties of pumpkin seeds were recorded as, 1.55 g/mL of true density, 0.61 g/mL of bulk density, 9.36% of moisture content, and 23.97o of angle of repose. The proximate compositions of pumpkin seed were found as 6.23% moisture content, 30.41% crude protein, 32.33% crude fat, 4.11% crude fiber, 5.10% ash, and 23.59% utilizable carbohydrate. At 160oC roasting temperature and 4 hr extraction time, a maximum oil yield of 39.22%, extraction efficiency of 86.40% and a minimum extraction loss of 1.64% was achieved. Thus, extraction parameters, such as oil yield, extraction efficiency, and extraction loss of pumpkin seed oil were significantly (P<0.05) affected by both roasting temperature and extraction time. The physiochemical properties of extracted oil, namely specific gravity, viscosity, moisture content, refractive index, free fatty acids, iodine value, acid value, smoke point, saponification value and peroxide value were investigated. At a roasting temperature of 160°C and an extraction time of 4 hr, these parameters have been determined: 0.88 specific gravity, 59.71 Cp viscosity, 0.51% moisture content, 1.480 refractive index, 2.64% free fatty acid, 113.12 I2g/100g iodine value, 7.79 mg KOH/g acid value, 150.73°C smoke point, 197.97 mgKOH/g saponification value, and 11.26 meq O2/kg peroxide value. The color values recorded were; 7.51 for L*, 3.49 for a*, and 6.99 for b*. The study found that most of the physicochemical values are nearly in line with the threshold levels advised by WHO/FAO (IV (110-143 I2/100g), RI (1.465-1.480), PV (10- 15meqO2/kg), SV (190-200 mgKOH/g), and SG (0.88-0.94)). Generally, this study offers crucial insights for product initiators in essential oils, food oils, and other industries to utilize pumpkin seeds as potential raw materials.