Calcium chloride provides a high concentration of calcium salts needed to activate sodium alginate.
Making coloured and flavourful translucent caviar-sized pearls from just about any liquid is possible by following a very simple process.
The ingredients used to make the spheres are as follows:
Calcium Chloride is hydroscopic and so must be kept in tightly-sealed containers.
Begin with a base liquid.
Performance Colours will add dramatic impact.
NB pH of the liquid should not be below 3.6 and should not contain large amounts of free calcium - a low pH will prevent the alginate from gelling, and too much calcium can cause the alginate to gel before the spheres have a chance to form.
Add Sodium Alginate to the base liquid
Add 1% of the liquid's weight. Blend the alginate with sugar or maltodextrin to disperse the particles, these will prevent the alginate clumping when it is added to the liquid.
Whisk in very gradually with a gentle whisking motion.
Leave the liquid to hydrate and stand until clear and free of air bubbles.
Create a Calcium Bath
Add 1% calcium chloride relative to the weight of the water.
Using a syringe, add the flavoured and coloured liquid to the setting bath drop by drop.
Use a Lotus Spoon (or slotted spoon) to stir the setting bath.
Thirty seconds is enough time for a durable membrane to form. Stirring for less time forms a more delicate skin.
Strain the spheres into a separate bowl and rinse.
Hints & Tips:
Add Sugar or Maltodextrin to disperse the particles, these will prevent the alginate clumping when it is added to the liquid.
A Caviar Box is an invaluable tool for preparing a large quantity of spheres quickly. (Why not serve in a Caviar Tin for extra impact?)
Getting the size and shape you want:
As the spheres sink through the setting bath, they form a sturdy skin. The bath should be deep enough to allow the spheres to sink for a second or so before they hit the bottom; working in a shallow bath will cause the spheres to flatten when they strike the bottom too soon. The roundness of the spheres is affected by two things: the distance the drops fall to the surface of the setting bath, and the viscosity of the base liquid. Experiment to find the ideal height from which to let the drops fall. A disc shape means you were too high, and the impact flattened the drop. An elongated shape means you were too low, and the drop did not have enough time to snap into a sphere.
Spheres not forming?
Keep in mind that every sphere you prepare removes a small amount of calcium from the setting bath. Eventually, the bath may be depleted of the calcium ions needed to trigger gelling.
If the base liquid already contains calcium, it may start to gel when the Sodium Alginate is added. To avoid this, add Buffer Salt (in liquids with a pH above 4.5 or Sodium Hexametaphosphate for more acidic liquids). Buffer Salt (Sodium Citrate) and Hexametaphosphate (Hex) are ‘sequestrants’ - compounds that mop up excess calcium ions by binding them so that they cannot interact with other molecules.
Rinse caviar pearls thoroughly to avoid after-taste.
Can they be prepared in advance?
RInsing the spheres will not halt the gelling process. They will gradually continue jelling until they lose their liquid centre, however sodium alginate is a soft setting gelling agent so the pearls will remain soft and jelly like. They can be prepared in advance and stored until needed. Store in same liquid they are made from, minus the alginate. Briefly rinse the spheres in clean water before serving.