Description of mechanical and relaxation behaviours of medium desiccated coconut under uniaxial compression using statistical response surface methodology

Mayrina Andriani, BE (mechanical)

Master's thesis

Abstract:

The study investigated the mechanical and relaxation behaviours of medium desiccated coconut under uniaxial compression by using statistical response surface methodology with Box-Behnken design (BDD) to determine the optimal conditions for medium desiccated coconut oil extraction. Three independent factors were examined being the force (kN), heating temperature (℃) and heating time (min) with each variable set at three levels. The BBD generated 17 experiments with twelve combinations of factors and five replicates at the center point. The universal compression testing machine (MPTest 5.050) of a maximum load of 5 kN was used together with a pressing vessel of diameter 30 mm and a plunger to record the compression data (dependencies between force and deformation as well as the relaxation force and time) on the medium desiccated coconut sample measured at an initial pressing height of 100 mm (sample volume of 7.07 x 10–5 m3). The compression experiments were done at a speed of 4 mm/min. The parameters calculated were the mass of oil (g), oil yield (%), oil expression efficiency (%) and energy (J). The data were statistically analyzed using the response surface regression technique at 5% significance level to obtain the regression models and the optimized processing conditions. Based on the compression results, the maximum mass of oil of 7.81 g, oil yield of 27.02 % and oil expression efficiency of 43.67 % were recorded for the combined factors of force: 4.8 kN; temperature: 40 ℃ and heating time: 45 min. The corresponding energy was 82.32 J. The P values of the lack of fit of the regression models were non-significant (P > 0.05) indicating reliability for predicting the calculated parameters. The optimized combined factors were force: 4.8 kN; temperature: 40 ℃ and heating time: 30 min. The percentage error values between the predicted and experimental validated ranged between 0.04 and 3.12 %. The relaxation time of 23 min increased the oil output at a lower temperature of 40 oC but it decreased at a higher temperature of 80 oC. The values of the spectral profiles (absorbance and transmittance versus wavelength between 325 and 600 nm) suggest that coconut oil can be utilized for the prevention of ultraviolet radiation problems on human skin.

Keywords

Oil bearing crops, linear pressing, processing factors, oil extraction, mathematical models

Language used: English

Date on which the thesis was submitted / produced: 31. 3. 2022

Thesis defence

• Supervisor: doc. Ing. Abraham Kabutey, Ph.D.

Czech University of Life Sciences Prague

Faculty of Engineering

Master programme:
Agricultural Engineering