Physicochemical characterization of traditional Ghanaian cooking oils, derived from seeds of Egusi (Citrullus colocynthis) and Werewere (Cucumeropsis manni)

Abstract

Traditional vegetable oils derived from Egusi (Citrullus colocynthis) and Werewere (Cucumeropsis manni) could prove to be an important commodity for Ghanaians, serving as a potential alternative source of common cooking oils. This study measured several physicochemical properties of Egusi and Werewere oils to describe and assess their nutritional quality, susceptibility to rancidity, and potential industrial applications. Physicochemical measurements were also taken on olive oil and coconut oil for comparative analysis and method validation. The solvent extraction yield of oil from seed of Egusi (39.94%) and Werewere (28.82%) fares well against the yields of common cooking oil seeds. Refractive index and iodine value tests for Egusi (1.471, 122.94) and Werewere (1.470, 106.134) reveal that the oils are likely rich in  unsaturated fats compared to olive and coconut oil. These measurements also suggest the traditional oils are susceptible to oxidative rancidity. Both Egusi and Werewere oils exceeded the FAO/WHO standards for permissible levels of impurity in edible oils. A high acid value (6.9) was measured for Egusi, suggesting the presence of free fatty acids. A high iodine value (122.9) was also measured for Egusi which suggests high unsaturation, likelihood to oxidation and susceptibility to rancidity. Overall, rigorous extraction and screening processes and additives may be required to produce Egusi and Werewere oils that are aligned with industry standards. The high extraction yield and prospective nutritional benefits of the oils are cause to explore further the use of these vegetable oils. © 2013 International Formulae Group. All rights reserved.

Keywords: Vegetable oil, physicochemical properties, unsaturated fats, nutritional quality