Effect of oven and sun drying on the chemical properties, lipid profile of soursop (Annona muricata) seed oil, and the functional properties of the defatted flour

Soursop seeds present a potential source of edible oil production. This work was aimed at determining the effect of oven and sun drying on the chemical properties and lipid profile of soursop seed oil as well as the functional properties of the defatted seed flour. The chemical properties, lipid profiles, and functional properties of soursop seeds dried for 0, 6, 12, 18, 24, and 30 hr, and 0, 1, 3, and 5 days, respectively, in the oven and on the sun using time T0 as the control sample were determined using oil quality indices, gas phase chromatography, and functionality tests for flours, respectively, with a view of highlighting the potentials of the defatted seed. The result of the study revealed that the chemical properties of oils for oven-dried and sun-dried seeds changed with drying technique and time, with iodine value being the more affected parameter, and peroxide value (PV) being the least. The control exhibited the highest free fatty acids (FFAs), peroxide value (PV), thiobarbituric acid (TBA) value, and saponification value compared with dried samples. The fatty acid profiling showed that the predominant fatty acids were C18:1n-9, C18:2n-6, and C16:0 and that unsaturated fatty acids (UFA), monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), and omega-fats were not significantly affected by the oven drying time. The mean PUFA content ranged from 31.72% with sundried seeds to 30.92% after 30 hr of oven-drying and was not significantly affected by the drying technique. The oils contained more n-6 (30.60%) fatty acids than n-3 (1.12%). The PUFA/SFA ratios [1.14-1.37] as well as the Atherogenic index (AI) [0.25-0.27] were acceptable because of the recommended range of FAO/WHO. PUFA/SFA, n-6/n-3, and Atherogenic index (AI) did not change much with the sun-drying technique compared with oven-drying. Flours from sun-dried seeds had better functional properties than oven-dried and more than 3 different types of proteins (based on isoelectric points of proteins). It can be concluded that soursop seed contains good quality oil, which can be exploited to improve nutrition. Manufacturers of animal feeds should explore the agro-industrial use of its oil and defatted seed flour.