Quality Characteristics of Oil Extracted from Seeds of Some Selected Curcubits Grown in the Southwest of Nigeria

Abstract

Cucumeropsis mannii, Cucurbita maxima, Cucurbita moschata, Lagenaria siceraria, and Cucumis sativus are among the species whose seeds and defatted cakes are particularly high in lipids and protein (28–40.49% in seeds, 61–73.59% in defatted cakes), making them valuable sources of both. This study aims to evaluate and compare the physicochemical properties and fatty acid profiles of oils extracted from selected cucurbit seeds, and to elucidate their quality, stability, and potential applications in human nutrition and industrial processes. Oils were extracted from seeds of selected members of the Cucurbitaceae family and analysed for physicochemical characteristics and fatty acid composition. A Soxhlet extractor was used to fully extract each of the chosen Cucurbit seeds to determine their oil content. The seeds studied were Adenopus breviflorus Benth (ADB), Fluted pumpkin (FLP), Snake tomato (ST), Watermelon (WM), Melon (ML), and Luffa sponge gourd (LSG). All were classified as oil seeds due to their relatively high oil yield, which ranged from 28.00% to 53.20%. The physicochemical properties of the extracted oils were within the following ranges: specific gravity (25 °C): 0.899–0.914; refractive index (25 °C): 1.472–1.476; free fatty acid (% as linoleic): 1.50–6.36; acid value: 2.50–12.72 mg KOH/g; iodine value: 84.26–125.20 mg I₂/g; peroxide value: 1.80–18.67 meq/kg; and saponification value: 112.70–208.50 mg KOH/g. Fatty acid analysis revealed that the oils were rich in unsaturated fatty acids. Linoleic acid was predominant (63% in ADB), followed by oleic acid (46.40% in FLP). The highest total unsaturated fatty acid content was recorded in LSG oil (82.46%), followed by WM (76.60%), ST (75.69%), ML (74.95%), ADB (74.70%), and FLP (73.83%). The saturated fatty acid content ranged from 10.85% (LSG) to 25.10% (ML), with palmitic acid (12.45%) and stearic acid (12.00%) being the major saturated fatty acids in melon seed oil. All the seed oils exhibited P/S values above 1, indicating good nutritional potential. The highest value was observed in LSG oil (6.49), while the lowest was in ST oil (1.70). ADB, FLP, WM, and ML had P/S indices of 2.83, 2.01, 2.77, and 2.27, respectively. The results confirm that the selected Cucurbit seed oils are of good quality and possess both nutritional and industrial significance. When refined, they have potential applications in the food industry as edible oils and in non-food industries such as cosmetics, soap production, and related products.