A few minutes before starting the expeller, steam of about 15-25 lbs. per sq. inch pressure should be admitted to the jacket of the tempering trough or the heating kettles, as the case may be, and the first meal entering the heating devices should be well cooked before pressing is commenced. However, if pressing is immediately commenced, the meal may not be properly cooked, and as the expeller is continuously drawing its feed from the cooker. It will be difficult to catch up with the demands of the expeller of providing a properly cooked meal. When pressing is started after the first charge to the cooker is properly treated, the supply of fresh meal should be continued to the cooker and the machine will continue to draw the proper meal throughout.