Yield, Physicochemical Properties, and Fatty Acid Profile of Vegetable Oil Extracted From Seed Coats of Strychnos pungens Soler. Fruits Collected in Chikomba, Zimbabwe.

Abstract

The study examined Strychnos pungens Soler. (family LOGANIACEAE) fruit as a potential source of vegetable oil. Ripe fruits collected from a forested site in Zimbabwe were processed to determine the partitioning of fresh and dry fruit biomass. The oil was extracted from the seed coat using a hand-operated screw press, and its physiological properties were analyzed. Seeds contributed the most to the fresh weight of the fruit, followed by the shell and pulp. The seed coat was a significant component of the seeds. The seed coat, but not the pulp of the fruit, was found to contain screw press-extractable oil, the yield of which was substantial, amounting to around 39% of the dry weight of the seed coat. The oil was found to have a high free fatty acid content and a moderate iodine value (83 gI₂/100 g), indicating a degree of unsaturation. Furthermore, the oil contained carotenoids and tocols, which serve as antioxidants that help to protect the oil from oxidation. The oil had a high content of monounsaturated oleic acid (78.3%), which is known for its stability and health benefits. The low levels of saturated and polyunsaturated fatty acids make it a high oleic oil. The volatile profile of the oil included compounds with pleasant fruity aromas that enhance its flavour and fragrance. The results highlighted the need for waste management strategies if S. pungens is industrialized as an oil crop. Significant waste, including shells, pulp, cake residue, and seed kernels, would need proper handling and valorisation. In summary, the research showed that S. pungens has the potential to be a valuable source of high-quality vegetable oil with good oxidative stability and health benefits, primarily due to its high content of oleic acid and antioxidant compounds.