Sodium Alginate
What it does
Thickener/stabiliser.
How it's made
From brown seaweed.
Sodium alginate is the sodium salt of alginic acid, one of the most useful seaweed-derived thickeners and gelling agents. It thickens sauces and fillings, stabilises ice cream and is famous in modern cooking for "spherification" — forming gel spheres when it meets calcium. It dissolves easily in water, unlike alginic acid itself.
It is made by extracting brown seaweed with alkali, which dissolves the alginate as sodium alginate. The extract is purified — filtered to remove debris and treated to remove colour and impurities — and the alginate is then recovered and standardised, typically by precipitation and re-dissolving, before drying.
The purified sodium alginate is dried and milled into a cream-coloured powder. Its special trick is that it forms a firm gel in the presence of calcium ions without needing heat, which is why chefs use it for spherification and manufacturers use it for heat-stable gels and fillings; being seaweed-based it is suitable for vegetarians and vegans.
Possible reactions
Generally safe.