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How can sodium alginate be used to make spherical foods?

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Plate of sushi rolls with salmon, vegetables, and rice wrapped in seaweed, served with chopsticks and a small bowl of soy sauce on a wooden table. — gastronomy A common rice dish of Japanese cooking is sushi. To make a type known as *maki-zushi*, a sheet of seaweed is spread with rice flavored with vinegar. Seafood or vegetables and garnishes are then placed on top. Finally, the whole sheet is rolled into a cylinder and sliced.

In the context of molecular gastronomy, sodium alginate is used to create spherical foods through a technique known as spherification. This process relies on the chemical reaction between sodium alginate and a calcium source to form a gelled "skin" around a liquid.

When a liquid containing sodium alginate is dropped into a calcium-rich bath (such as a solution of calcium chloride or calcium lactate), the calcium ions react with the alginate molecules. This reaction causes the outer layer of the liquid droplet to instantly solidify into a thin, flexible gel membrane, effectively trapping the liquid inside a sphere. This method allows chefs to create culinary items that resemble caviar or larger liquid-filled pearls, which burst with flavor when consumed. While sodium alginate is a key gelling agent in this process, it is distinct from other thickeners like agar, which solidifies based on temperature changes rather than ionic reactions with calcium.1