Characteristics and Composition of Watermelon Seed Oil and Solvent Extraction Parameters Effects

Watermelon seed oil characteristics were evaluated to determine whether this oil could be exploited as an edible oil. Hexane extraction of watermelon seeds produced yields of 50% (w/w) oil. The refractive index, saponification and iodine value were 1.4712 (at 25 °C), 200 mg KOH/g and 156 g I/100 g, respectively. The acid and peroxide values were 2.4 mg KOH/g and 3.24 mequiv/kg, respectively. The induction time of the oil was also 5.14 h at 110 °C, which was measured for the first time. Total unsaturation contents of the oil was 81.6%, with linoleic acid (18:2) being the dominant fatty acid (68.3%). Considering that the watermelon seed oil was highly unsaturated, the relatively high induction time might indicate the presence of natural antioxidants. In addition, the influence of extraction parameters on extraction of oil from watermelon seed with hexane as a solvent was studied at several temperatures (40, 50, and 60 °C), times (1, 2, and 3 h) and solvent/kernel ratios (1:1, 2:1, and 3:1). The oil yield was primarily affected by the solvent/kernel ratio and then time and temperature, respectively. The protein content of the oil-free residue was 47%.