A Comparative Study of the Properties of Selected Melon Seed Oils as Potential Candidates for Development into Commercial Edible Vegetable Oils

Abstract

A comprehensive compositional and characterization study was carried out on five seed oils from varieties of the melons Citrullus lanatus and C. colocynth in order to evaluate their suitability for large-scale exploitation as edible vegetable oils. The oils were extracted by Soxhlet with a 3:1 mixture of n-hexane/2-propanol with yields that ranged from 24.8 to 30.0% (wt/wt). The refractive indices and relative densities of the oils fell within the narrow ranges of 1.465–1.469 and 0.874–0.954 g/cm³, respectively. Saponification values ranged between 182.1 and 193.8 mg KOH/g, whilst iodine values (IV) ranged from 95.8 to 124.0 (Wijs). The ranges of the values for free fatty acid (AV), 1.2–4.0 mg KOH/g, peroxide (PV), 1.1–10.9 meq/kg and p-anisidine (p-AV), 0.2–9.0, indicated that secondary oxidation products were barely present. GC analysis gave total unsaturation contents of 67.93–82.36%, with linoleic acid (18:2) being the dominant fatty acid (55.21–66.85%). The GC results agreed closely with those from proton NMR analysis of the fatty acid classes. The physicochemical and compositional properties determined in this study show that the qualities of the test Cucurbitacea seed oils are highly comparable to those of soybean, sunflower and groundnut seed oils. Therefore, the test melon seed oils could be developed into commercial products to serve as alternate vegetable oils in Southern and West Africa, the regions where these melons grow.