The term “press cake” refers to the solids left over after something has been pressed to separate the solids and liquids it contains. There are a wide range of uses for this substance, depending on the product it comes from. As a general rule, consumers rarely encounter pure press cake, because it is the result of an industrial process, although they undoubtedly use products made with it.
One well known example of press cake is cocoa solids, the solid materials left behind after cacao beans are pressed to extract their cocoa butter. Cocoa solids can be refined to make cocoa powder, and they can also be blended with a variety of ingredients, including cocoa butter, to make eating chocolate. Depending on how cocoa solids are treated, they can be used in a variety of chocolate products, from chocolate coatings made with cocoa solids and whatever oils are cheap at the moment to gourmet truffles made from high-grade base ingredients.
Another type of press cake is pomace, the material which remains after olives are pressed to make olive oil, or after various fruits are pressed to make juice and wines. Pomace is used as fertilizer in many regions, and it can also be processed to make things like pomace wine, or fed to animals. In some cases, fruit pomace is processed to make various concentrated products, such as health supplements. Fruit pomace can also be distilled to extract useful vitamins and other materials which it contains, as is the case with grape pomace, which is processed for for its grape seed oil.
The pressing of various nuts and grains for oils also produces press cake, which some factories burn in their furnaces to generate energy. These operations can also sell their press cake as animal fodder, or plow it back into the soil to enrich the land. Cake also remains after soy beans are pressed to make soymilk, in which case it may be fermented to make other soy products.
While press cake lacks most of the oils and juices which the original product contained, it can still be quite useful and sometimes valuable. It can still contain many vitamins and minerals, along with the chemicals which make foods taste or smell a particular way. Most factories which produce press cake find a use for it, both out of a desire for efficiency and because it is hardly waste material.