Sodium Alginate is a gum derived from the cell walls of brown algae. It is widely used in the food industry to thicken and ‘gel’ foods. For example, the pimentos in olives are one of many ‘solids’ that are actually gels made with sodium alginate. It is an extremely powerful thickener with the ability to absorb 200 – 300 times its own weight in water.
In modernist cooking, sodium alginate is most commonly used in spherification. When it comes into contact with calcium lactate or calcium lactate gluconate a thin jelly like membrane is formed thus encapsulating a liquid substance.
When using in Reverse Spherification mix with distilled water at a ratio of 0.5% (5g per 1000g) using an immersion blender. Note this may take longer than normal due to the gummy nature of the alginate. Periodically scrape down the blender to ensure all the alginate is thoroughly mixed into the water. This will be your curing bath.
When using in Basic Spherification mix with the spherification liquid at a ratio of 1% using an immersion blender. You may also want to add xanthan gum to increase the density of your liquid.