Consists of the cell contents of yeast without the cell walls; they are used as food additives or flavorings, or as nutrients for bacterial culture media. It is made by adding sugar to yeast in a warm environment. As the yeast expands, the walls of its cells soften. The mixture is then spun in a centrifuge and the loosened cell walls are whisked away. They are often used to create savory flavors and can be found in a large variety of packaged foods. They are rich in B vitamins.