Processing of Bulk Hemp Seeds by Estimating the Optimum Input and Output Parameters and the Description of the Theoretical Deformation Energy Under Uniaxial Compression Loading

This present study adopted the Box-Behnken Design (BBD) with Response Surface Methodology (RSM) to identify the optimum input processing factors (heating temperature: 40, 50 and 60 °C, heating time: 30, 45 and 60 min and pressing height: 60, 80 and 100 mm) for estimating the oil output parameters (mass of oil, oil yield and oil expression efficiency) and deformation energy. The mechanical properties examined were the hardness and secant modulus of elasticity. Based on the full quadratic model, which includes both significant and non-significant terms, the optimal input processing factors were determined to be a heating temperature of 60 °C, a heating time of 52.5 min, and a sample pressing height of 100 mm, with coefficient of determination (R²) values ranging from 0.68 to 0.95. The linear models with the significant terms predicted the mass of oil of 33.36 g, oil yield of 21.5 %, oil expression efficiency of 65.47 % and the experimental deformation energy of 1080.82 J. The percentage error values between the experimental and theoretical deformation energies were from 1.35 to 28.31%, suggesting that the varying input processing factors affected the coefficients of the tangent curve model for fitting the experimental force-deformation curves. The hardness and secant modulus of elasticity values ranged between 3.65 and 7.09 kN/mm and 123.98 to 150.39 MPa, indicating that the varying input processing factors had a significant effect on the stiffness of the bulk hemp seeds. These findings are useful for modelling and optimising the mechanical behaviour of oilseeds using a mechanical screw press to enhance oil recovery efficiency.