
Figure 1. A thermal analysis of raw corn germ as measured with a DSC Q1000 showed the TG and TM to be consistent with literature values for similar materials.
Corn oil typically is recovered from the corn germ through a solvent-based process using hexane. Due to capital equipment requirements and special handling and disposal considerations, the use of hexane is considered a rather expensive process. Unfortunately, water-based methods for oil recovery have not been successful because the yields of corn oil are much less than those obtained using hexane extraction.

Figure 2. Samples were tested in a LIN pilot-scale process that incorporated a helical screw conveyor.
A thermal analysis of the unprocessed germ was performed to identify whether ambient or cryogenic grinding would be recommended. The transition temperatures were measured on a differential scanning calorimeter (DSC). The DSC output shown in figure 1 identified a glass transition temperature (TG) for the starch component at around -72°F (-58°C) and a melting temperature (TM) for the oil component at around -4°F (-20°C). These results were consistent with literature values for similar materials. Therefore, based on the rather low TG, the material was considered appropriate for using cryogenic conditions in grinding to expose sufficient surface area to maximize the oil extractability.

Figure 3. The cylindrical tube at the top of the helical screw conveyor was fitted with a LIN injection manifold and appropriate controls to introduce the refrigerant into the process. The body of the conveyor was insulated to mitigate the cryogenic burn hazard and maximize cooling efficiency.

Figure 4. The particle size distribution for the cryogenically ground corn germ (as measured with a Horiba LA-910) demonstrated that LIN was an effective and efficient method of controlling in-feed temperature.

This table shows the average settings and run-time calculations for several Microtec UTM-200 corn germ trials conducted using LIN.
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