Optimization and characterization of ultrasonically extracted oil from watermelon seeds using response surface methodology: a pathway to biodiesel and epoxy oil production

The growing demand for renewable energy and sustainable materials has led to interest in the production of unconventional oil such as watermelon seeds for the productions of biodiesel, epoxy resins, and polyols. The oil is extracted by ultrasonic-assisted solvent extraction and RSM is used to optimize the process parameters. The extracted oil physico-chemical composition, mineral content, thermogravimetric properties, functional groups, and fatty acid profiles were analyzed to check the potential of the oil for producing biodiesel, epoxy resin, and polyol. Under optimal conditions of 48.2 °C, 46.3 min, and solid-solvent ratio of 0.067, oil yield was 47.5%. Fatty acid composition included palmitic (5.63%), stearic (3.04%), oleic (19.25%), linoleic (69.96%), and linolenic acid (2.12%). The physico-chemical characteristics of the oil include an iodine value of 124.8 g I₂/100 g, acidity value of 1.02 mg KOH/g, and saponification value of 201.4 mg KOH/g. The mineral composition also shows its suitability for biodiesel, epoxy resin, and polyol production. The watermelon seed oil properties indicate its suitability for bioenergy and biased material production which has great potential for bio-based industrial applications.