Sodium alginate. Product from different types of algae (Fucus, Laminaria, Macrocrystis ...). It has the peculiarity of forming gels in the presence of calcium. As with any hydrocolloid, it needs a part of water to hydrate.
Properties: Gelling when it interacts with calcium media.
How to use: For direct spherification, mix with the desired preparation. For reverse spherification, mix in the water bath.
Application: Any liquid with a pH ≥4 and with a water content greater than 80% (direct spherification).
Observations: By itself it acts as a thickener. Always use mineral water for reverse spherification. In fatty media it presents dissolution problems. In fatty media it finds incompatibilities. In alcoholic environments it offers problems depending on the degree of alcohol and the lack of water.
Elaborations: Direct spherification / Reverse spherification