Modeling and optimization of laboratory-scale conditioning of Jatropha curcas L. seeds for oil expression

• Dry heating Jatropha seeds before pressing increases oil extraction yield;
• Higher yields are attained at higher temperatures and shorter times (90 °C/10 min);
• Higher yields are attained at lower temperatures and longer times (60 °C/50–60 min);
• The best time/temperature binomial conditions mainly depend on economical aspects.

The effect of conditioning of Jatropha curcas L. seeds on the yield of oil extracted by screw pressing was studied. A pressing test was performed with seeds without heating treatment and the extraction yield was 84.0%. Modelling dry conditioning of seeds and optimization of operation conditions were performed using Response Surface Methodology with a total of 11 dry conditioning experiments, following a central composite rotatable design as a function of temperature (52–108 °C) and time (8–92 min). An increase in the extraction yield occurred in all the experiments, with a maximum of 5.6% (w/w) increase, indicating the need to perform seed conditioning before mechanical extraction. The minimum oil contents in the press cakes, and therefore the highest extraction yields (c.a. 88%, w/w) were obtained with seeds treated at higher temperatures and shorter periods of time (e.g., 90 °C/10–20 min; 80 °C/30 min) or at lower temperatures and longer periods of time (e.g., 60 °C/50–60 min). Steam treatment at temperatures of 100, 110 and 120 °C resulted in seed softening and press clogging and no oil could be extracted.

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