Spherees18

Sodium Alginate & Spherification

Update: for a practical step by step guide to our reverse spherification recipe of oyster infused dashi click here.

Sodium alginate is a thickening and gelling agent that forms heat stable gels in the presence of calcium. This property allows cooks to make small gelled spheres, in a technique known as spherification. Sodium alginate has been used in the food industry for many years for the production of gel-like foods – for example, the pimento stuffing in prepared cocktail olives.

Alginate, or alginic acid, is extracted from brown algae and most commonly available as a sodium salt.

Alginate, or alginic acid, is extracted from brown algae and most commonly available as a sodium salt.

It is composed of long strands made up of carbohydrate units – these long stands allow it to act as a very efficient thickening agent at low concentrations (e.g. 1%). Gels formed from alginates have the amazing ability of withstanding heating to temperatures as high as 150ᵒC without melting, allowing them to be used in hot applications such as broths.

When alginate is added to a liquid, it will act as a thickener. In the presence of calcium ions, a mixture containing alginate will form a gel. The calcium ions insert themselves between individual alginate strands and will allow them to interlock and form a gel.

 

Alginate should be added to the liquid at a final concentration of 0.5 – 1%. The solution however, does not need to be heated with the additive in order to gel (unlike agar and carragenan) so can be used with raw preparations. When this solution is pipetted into a solution of calcium chloride or calcium lactate (at a concentration of 1-2%), small beads or gelled threads can be formed. These beads can be then be removed from the setting bath, rinsed and then consumed immediately to provide a solid bead with an liquid centre – the viscosity of the liquid inside will depend on the amount of alginate initially added.

Spherification methods

There are two main methods for creating such spheres, which differ based on the calcium content in the product to be spherified. For substances containing no calcium, the liquid is mixed with sodium alginate, and dripped into a cold solution of calcium chloride or calcium carbonate. ‘Reverse’ spherification, for use with substances which contain calcium, requires dripping the substance into an alginate bath. Both methods give the same result: a sphere of liquid held by a thin gel membrane, texturally similar to caviar.

Basic Spherification

Spherification is a process in which flavoured liquids are manipulated using a gelling agent to form a thin membrane around the liquid and result in sphere shaped capsules which burst in the mouth. The spheres are often referred to as caviar, ravioli or bubbles.

Basic spherification is easier & ideal for obtaining spheres with an ultra thin membrane.

The Science

For this method the sodium alginate is dispersed into the flavoured and the calcium is dissolved in the water ‘bath‘. The spherification liquid cannot be too acidic or high in calcium. pH level must be above 3.6. Generally a 0.5% sodium alginate solution works well

1% Calcium bath.

Equipment/ ingredients

-Sodium alginate

-Calcium lactate/gluconate

-Hand held immersion blender

-Pipette or syringe (for caviar)

-Precision scales (preferably 0.01g)

Reverse Spherification

The technique of Reverse Spherification is much more versatile than Basic Spherification as it can make spheres with almost any product.

Is the reversal of basic spherification with the liquids in which the sodium alginate and calcium are dispersed in.

This process  can be used to form spheres with liquids which are high in dairy, alcohol or acidity. There spheres can be made in advance and served later without compromising texture or flavour as the gelling process stops once the spheres are removed from the sodium alginate bath and ‘rinsed’ in water. The spheres will have a thicker membrane which is great for plating, however it does result in an added texture of a solid jelly membrane.

The Science

1% to 2% of calcium is added to the flavoured liquid, this is however very variable and will depend on the liquid’s calcium content. The sodium alginate ‘bath’ with a concentration of approximately 0.5% using a hand held immersion blender.

 Equipment/ ingredients

-Sodium alginate

-Calcium lactate

-Precision scales (preferably 0.01g)

-Hand held immersion blender

-Rounded measurement spoons (for larger spheres)

Hints, tips, tricks

Avoid  Clumping

This is most easily done by adding the powder little by little to the liquid, while mixing constantly with an electric hand blender.

Disperse well!

Sodium alginate may take a while to disperse fully into water with a hand held immersion blender, this process may take up to 5 minutes. If the alginate is not properly dispersed, small lumps will be visible when the solution coats the back of a spoon. Excessive whisking of the base liquid during preparation should be avoided, since the air bubbles tend to stay trapped in the solution due to its thickness.

Bubble free spheres

Leave the sodium alginate solution to rest in order for the trapped air bubbles to escape, this can take up to 24 hours

For basic spherification:

-if the liquid in which the sodium alginate solution is too thick e.g. purees, mix the sodium alginate in water, then add to flavoured liquid

-mix the sodium alginate into 1/3 of the liquid, then add the rest of the liquid, this reduces the amount of air bubbles trapped in the solution

For reverse spherification:

-Allow the sodium alginate bath to come to room temperature before using, to reduce the solution’s viscosity

-Rotate the spheres while in the sodium alginate bath to ensure the full surface are of the sphere is ‘cooked’ equally and has a uniform membrane thickness on all sides

Consider Calcium Content

Do not mix sodium alginate into tap water or mineral water if it has a high calcium content as this will trigger the gelling process before you have even started

Keep a clean bath

Keep the calcium (for basic spherification) or sodium alginate (for reverse spherification) ‘bath’ clean, any small particles floating around from previous spheres which have ruptured may disturb the process. Simply use a fine sieve to remove any particles

Correcting Acidity for Spherification

The Basic Spherification process  does not work if the main ingredient is too acidic (PH<5). If necessary , the acidity can be reduced by adding sodium citrate to the main ingredient (if watery liquid) or the water used to reduce the main ingredient density (if thick liquid) always BEFORE you add the sodium alginate.

 

Basic Spherification Video Guide

Reverse Spherification Video Guide

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