Modeling of Linear and Non-linear Compression Processes of Sunflower Bulk Oilseeds

Research on Mechanical–Structural and Oil Yield Properties during Xanthoceras sorbifolium Seed Oil Extraction

Products from Xanthoceras sorbifolium Bunge seed have gained extensive attention for various applications, especially in the fields of edible oils and industrial applications. In order to study seed kernel mechanical–structural behavior and oil yield mechanisms during extrusion, we set up a self-developed texture analyzer with in situ microscope observation. Test results indicated that seed kernel oil yield and pressing energy showed an approximately parabolic shape under pressing strain, and maximum oil yield reached 25.7%. Only local tissue damage occurred on seed kernels at strain 45–85%, cracks formed from the kernel edge to the inside zone and small cracks obviously increased in number, corresponding with the oil yield and energy–strain curve. The effect of speed on oil yield showed an opposite trend to strain effect; high pressing speed led to lower oil yield due to the short time for oil precipitation and lower pressing energy. Dwell time obviously promoted oil output within 600 s. Drying temperature had a negative effect due to structural change. Oil yield was almost zero at temperatures below 120 °C. The oil yield and pressing energy relation curve was obtained by polynomial fitting; optimal seed kernel oil pressing conditions were strain 95%, 0.1 mm/s, 20 °C, dwell time 600 s. The research provides in-depth theoretical guidance for Xanthoceras sorbifolium Bunge oil production.

Investigation of Heating and Freezing Pretreatments on Mechanical, Chemical and Spectral Properties of Bulk Sunflower Seeds and Oil

The present study examined the effects of heating and freezing pretreatments on the mechanical, chemical, and spectral characteristics of sunflower seeds and oil under a linear compression process involving a universal compression-testing machine and a pressing vessel of diameter 60 mm with a plunger. The heating temperatures ranged from 40 to 80 °C and freezing temperatures from −2 to −36 °C at constant heating time of 30 min. The pretreated samples of initial height of 80 mm (22.6 × 10−5 m3) were compressed under a preset load of 100 kN and a speed of 5 mm/min. The results showed that oil expression efficiency significantly increased (p < 0.05) with increased heating temperatures but decreased with freezing temperatures. The lowest energy per volume oil of 22.55 ± 0.919 kJ/L was recorded at 80 °C compared to 26.40 ± 0.307 kJ/L noticed at −2 °C and control (25 °C) of 33.93 ± 3.866 kJ/L. The linear regression equations expressing oil expression efficiency, energy per volume oil, peroxide value, and free fatty acid, dependent on heating and freezing temperatures, were described with coefficients of determination between 0.373 and 0.908. Increased heating temperatures increased the UV absorption rate of the oil samples at a wavelength of 350 nm. The study is part of the continuing research on linear compression modeling of all processing factors, whereby the results are intended to be applied to the non-linear process dealing with a mechanical screw press to improve the oil extraction process.