Algin, Sodium Alginate
Algin is an ingredient required for the "Spherification" process, a hydrocolloid-based technique resulting in a gel coated sphere which houses a liquid center. This sodium alginate is usually paired with a sister ingredient of calcium salt, or calcium chloride, to complete the spherification process. A variety of liquids can be used including many fruit juices, to create spheres ranging in size from tiny droplets (often called caviar) to grape-sized balls.
Chicago chef Grant Achatz is one of the pioneering users of molecular gastronomy, and his cookbook Alinea contains recipes and techniques for cooking with Sodium Alginate and other mg ingredients.