Sodium citrate is a sodium salt made from citric acid obtained by fermentation (from sugar).
Use 0.5 to 2g/liter (0.2%) to counteract the presence of calcium ions in the solution. Dissolve the citrate before adding and mixing the calcium-sensitive hydrocolloids. Afterwards, a dosed contribution of calcium will encourage a better controlled setting (duration, strength).
Adding astringent flavouring: use less than 1%.
Sodium citrate reduces the impact of free calcium in solutions and better dissolves calcium sensitive ingredients such as alginate or gellan. Sodium citrate is used as a spice that would bring a bitter note reminiscent of citrus.
Sodium citrate acts as a calcium trap. The calcium is not destroyed or altered. Depending on the pH and other ingredients, calcium can become available again and weld the alginate molecules together.
A gel solution formed from alginate and calcium in which sodium citrate has been dissolved will be less homogeneous and will give more water than a solution made without. One must consider the advantages of a slow setting allowing to mould the solution with the disadvantage of having a slow and less regular gelling.
Sodium citrate is recommended in spherification to reduce the acidity of acidic ingredients, especially from citrus fruits, but an excess of it alters the taste. It does not give viscosity; has no smell but an astringent / bitter and salty taste. Very soluble: over 70g / 100ml.