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2. Methodology
2.1. Materials
Jatropha seed at a storage moisture content was used for the drying experiment. The detailed materials used during the drying experiments was described in the study of the effects of temperature and pretreatment of seeds on the drying process and physical appearance of different collections of Jatropha seeds and has been presented elsewhere (Keneni and Marchetti, 2018). A bowl-shaped mortar and pestle made from stone were used for the crushing pretreatment of Jatropha seeds. Three different sieves with openings of 500µm, 1mm and 2mm woven cloth (Control Group, 15-D2245/J, 15-D2215/J and 15-D2185/J) were used to estimate the particle sizes of the crushed seeds. The seed samples were weighed on a digital balance machine having 0.01 mg accuracy (Mettler-Toledo, PG 5002 Delta Range, Switzerland). The samples were placed on pyrex glass petri plates for drying. The drying experiments and determination of initial and residual moisture contents of the seed samples were performed using a heating furnace (Narbetherm P300, Germany).
2.2. Seed drying experiments
The seed drying experiments were perfumed in the Laboratory of Norwegian University of Life Sciences (NMBU), Faculty of Science and Technology. The initial moisture contents of the Jatropha seed samples used for this experiment has been determined prior to this experiment (Keneni and Marchetti, 2018) by drying 15g of the seed samples at 105oC for 24h (Bamgboye and Adebayo, 2012; Garnayak et al., 2008; Siqueira et al., 2012; Subroto, 2015). Accordingly, the moisture content of the seeds was found to be 6.811%, and thus, the moisture content of the seed samples utilized for the experiment was in the range of the storage moisture content (6-10%) reported for seeds of Jatropha (Brittaine and Lutaladio, 2010).
The pretreated (crushed seeds, CS) and non-pretreated (the whole seeds, WS) were used for the drying experiments. For the crushing pretreatment process of Jatropha seeds, a bowl-shaped mortar and pestle made from stone were used. After crushing, the particle sizes of the pulverized seeds were estimated by three different stainless steel sieves with openings of 500µm, 1mm and 2mm woven cloth (Control Group, 15-D2245/J, 15-D2215/J and 15-D2185/J). For every drying experiment, ca. 15g of Jatropha seeds were used and both treatments were duplicated. Thus, the crushed seeds used in the drying experiment was a mixture of four particles sizes. The average proportions (%) of the particle size of crushed seeds (PSCS): PSCS >2mm, 2mm > PSCS >1mm, 1mm > PSCS >500µm and PSCS