Oxidation Studies On Sesame Seed Oil

Six sesame seed oils have been extracted from Sudanese seeds of known origin. The oils have been subjected to a variety of storage tests and the relative stabilities have been assessed by measuring the average odour scores (AOS), average flavour scores (AFS), refractive indices (RI), colours, peroxide values (PV), conjugable oxidation product (COP) values, oxodiene values (OV) and Kreis test of oil samples during subjection to the different storage tests. Component fatty acids, trace elements and tocopherol contents of the oils have been determined. Sesamin and sesamolin have been extracted and purified. The purities and identities of sesamin and sesamolin and the purity of a commercially purchased sesamol, used as standards, have been assessed by six independent techniques. The use of Thin Layer Chromatography (TLC) together with optimised conditions for densitometry, has led to a method for the analyses of pure sesamol, sesamin and sesamolin. Interferences occur when analysing the unsaponifiables of the oils for these compounds. Optimisation of Gas—-liquid Chromatographic (GLC) conditions led to a method for separation of sesamol and sesamin standards. They were determined in the oils by direct injection of the ethanolic solutions of the unsaponifiables. Sesamolin was determined as "bound sesamol" after acid hydrolysis of the sesamolin present in the unsaponifiables. A High Performance Liquid Chromatographic (HPLC) method has been developed for the determination of sesamol, sesamin and sesamolin levels in the oils. Separation and analyses of the compounds have been achieved by direct injection of the ethanolic solutions of the unsaponifiables. Relationships between the compositional factors possibly affecting stability and assessment of the relative autoxidative stability of sesame seed oil have been discussed. A preliminary study into the investigation of sesamol oxidation was carried out. Sesamol was oxidised in different solvents under ultra violet (UV) light. The product(s) of the reaction were analysed by HPLC and a new peak was detected. The fraction responsible for this peak was collected by HPLC and examined by TLC; UV absorption spectrometry and chemical methods. Results obtained indicated the presence of carbonyl group(s) in the new compound.