Spherification is a molecular gastronomy technique created by the famous chef Ferran Adria. It produces a sphere of a liquid surrounded by a delicate membrane of jelly. The spheres need to be handled carefully and break very easily when placed in the mouth, releasing an explosion of flavor. The resulting spheres have been given names like caviar and ravioli depending on their size.
There a couple of versions of the spherification process: basic spherification and reverse spherification. Basic Spherification is done by mixing the main liquid ingredient with sodium alginate and dropping one scoop at a time in a bath of calcium. The sodium alginate reacts with the calcium forming a jell. In Reverse Spherification the main liquid ingredient is mixed with calcium and the bath is a solution of sodium alginate.
Basic Spherification creates a thin delicate membrane based on the main ingredient but the problem is that once the sphere is removed from the calcium bath, the jellification process continues and the sphere will eventually convert into a solid jelly ball. So that diners get the best experience, spheres created with the basic spherification method need to be served immediately after preparation. Another disadvantage of basic spherification is that jellification does not occur if the main ingredient is to acidic. Examples of Basic Spherification are "Spherical Mango Ravioli" and "Liquid Pea Ravioli". Learn more about Basic Spherification.
Reverse Spherification was invented to solve a few of the problems of basic spherification. With reverse spherification it is possible to create spheres of liquids with high calcium content or alcohol content. Another benefit of this spherification method is that jellification stops when the spheres are removed from the bath so they can be made several hours before serving. Examples of Reverse Spherification are "Yoghurt Spheres", "Liquid Mozzarella Spheres" and "Spherical Olives" (shown below). Learn more about Reverse Spherification.