The influence of the bed volume on the kinetics of watermelon seed oil extraction was evaluated in this study. Watermelon seed oil was extracted using different extraction cells (S-1 = 34 mL, S-2 = 66 mL and S-3 = 100 mL) at different temperatures (40, 60 and 80 degrees C) using the sample mass/solvent volume ratio as the fixed sizing criteria (w/s = 0.30). The extraction kinetics were mathematically described using the Peleg, Fick and second-order models. Samples were extracted in batches using pressurized liquid extraction (PLE) with ethanol as the solvent for different extraction times. Oil extraction yields ranged from 24.69 to 37.21 g oil/100 g of seeds, and the concentration of total phenolic compounds ranged from 2.44 to 3.84 mg of gallic acid equivalents (GAE)/g of seeds. All kinetic models showed a good fit to the experimental data, but the second-order model better predicted the behavior of data, with high coefficient of determination (R-ajd(2)) and low root-mean-square deviation (RMSD) values. The different extraction cells did not affect the total extraction yield, but affected the extraction parameters obtained in the models. The effective diffusivities were dependent on temperature and ranged from 9.10 x 10(-6) to 2.07 x 10(-5) m(2)/s. The activation energy ranged from 11.43 to 18.54 J/mol. (C) 2016 Elsevier B.V. All rights reserved.