ABSTRACT
Lipids are removed from lipid-containing materials by two methods: mechanical crushing and solvent extraction. Small volume processors prefer mechanical crushing to avoid having to build a costly solvent extraction system. Oilseeds come into the mills along with stems, leaves, stones, sand or dirt, and sometimes weed seeds. The first oilseed application for extrusion was rice bran. Rice bran comes into a solvent extraction plant as a fine powder, which makes rice bran very difficult to extract. The powder also contains an enzyme, lipase that splits triglycerides into free fatty acids. Cooking is excellent preparation for most oilseeds and is necessary for those too soft to withstand the pressures generated within a screw press. Cooking hardens those oilseeds, similar to the way cooking hardens eggs. Horizontal cookers are arranged in clusters of separate vessels, one for cooking, three or more for drying. Each vessel is steam-jacketed and contains a revolving shaft with protruding stirring paddles.
