Asian Research Journal of Current Science

Roselle (Hibiscus sabdariffa L.) seeds are an underutilised by-product with considerable potential as a source of edible oil because of their high content of unsaturated fatty acids and bioactive compounds. This study aimed to optimise screw-press extraction conditions for roselle seed oil yield, residual oil content in the cake, and oil recovery, and to evaluate the effect of steaming pretreatment on the quality of the extracted oil. The study was conducted at the Department of Postharvest Technology, Advanced Center for Agricultural Research and Education (ACARE), Yezin Agricultural University (YAU), Myanmar. Steamed roselle seeds were screw-pressed at different temperatures and moisture contents. Response surface methodology (RSM), based on a central composite rotatable design, was used to optimise the extraction conditions. Pressing temperature and seed moisture content significantly influenced all response variables. The optimum extraction conditions were 160°C and 8% moisture content. The quadratic models were highly significant (p < 0.001) and showed close agreement between the experimental and predicted values (R² = 0.9902–0.9914). Quality evaluation showed that steaming pretreatment significantly reduced free fatty acid content and increased iodine value and antioxidant activity compared with the control (without steaming) (p < 0.05). However, peroxide value, saponification value, refractive index, and specific gravity were not significantly affected (p > 0.05). The combined use of steaming pretreatment and optimised screw-press extraction improved extraction performance and selected oil-quality characteristics, providing information for the development of efficient roselle seed oil processing conditions.