E401: Sodium alginate

What is E401?

Sodium alginate is the sodium salt of alginic acid, a natural polysaccharide found in the cell walls of brown seaweeds. Known as E401, it dissolves in water to form a viscous solution and sets into a gel in the presence of calcium.

Origin and production

It is extracted from brown seaweeds such as kelp: the seaweed is treated with an alkaline solution, and the alginate is then purified and converted into its sodium salt.

Why is it used?

Sodium alginate thickens, stabilises and gels foods. It helps ice cream and frozen desserts resist ice crystal growth, holds fillings in cakes and pastries, and binds frozen meals and pasta dishes; it is also behind the 'spherification' technique used to make liquid-filled pearls.

Vegan, vegetarian and halal

Sodium alginate comes from seaweed and is suitable for vegans and vegetarians. It is commonly used as a plant-based alternative to gelatin and does not usually raise halal or kosher concerns.

Safety and regulation

Sodium alginate is authorised as a food additive in the EU and was re-evaluated by EFSA, which did not consider a numerical acceptable daily intake necessary for alginates.

Common in