CHARACTERIZATION OF PREPARATION PARAMETERS FOR IMPROVED SCREW PRESSING OF CRAMBE SEED

Screw pressing of niche oilseeds such as crambe may be a viable alternative to solvent extraction of oil. Cooking before pressing is known to improve oil recovery. Use of well–defined cooking conditions of time and temperature was expected to aid characterization of the relationship between cooking and press performance, and to reduce soluble seed protein according to a fundamental kinetic model. A pressure cooker modified to permit both steam injection and vacuum permitted the cooking of crambe seed at well–defined conditions of 90³C to 120³C for 5 to 20 min. Oil recovery increased with increasing cooking temperature and time to a maximum of 75.9% at 100³C and 12 min, versus 70.9% for uncooked seed, and a low of 70.6% at 120³C and 20 min. Oil recovery and press rate were nonlinear functions of cooking temperature and time. A cooking index based on soluble protein decreased according to a modified thermal processing model with D0 and z values of 3.3 min and 28³C, respectively. The index was also useful for identifying optimally cooked seed. Oil recovery increased with decreasing seed moisture content to a high of 82.5% recovery at 3.5% m.c. The approach described here may be extended to the tuning of other screw presses for crambe and other oilseeds.