Last week we talked about the Spherification, a technique of the molecular cuisine that allows the transformation of a liquid mixture into solid spheres.
This technique requires an accurate preparation, but it has a limit.

In fact, the Spherification does not apply to foods with a high percentage of calcium, so it has been necessary to find a new technique to obtain this result.

The solution was found through the exchange of the factors that allow the gelling, so the calcium salt was added to the food, subsequently immersed in a bath of water and sodium alginate.
This technique, which goes in the opposite direction of the normal Spherification process, is called reverse spherification.

The reverse Spherification allows the preparation of spheres with a liquid heart without changing the flavour of your ingredients.
As we said before, in this case the calcium required for gelation is contained in the mixture you want to transform into spheres.

At this point we can divide the entire process of reverse Spherification in 4 phases to better understand how it works.

The stages of Reverse Spherification

1) First, you have to prepare the bath of sodium alginate. To give some references, 2 g of sodium alginate are sufficient for 2 cups of water (450 ml). Stir constantly with a whisk.

2) Then mix the food that you want to transform into spheres and let it rest for at least 30 minutes, so that the air bubbles disappear.

If your food has a low level of calcium, you can add it to your mixture.
If the food is too acidic, you will not be able to get a good result.
Moreover, if it is too liquid it will not turn into a perfect sphere.

The calcium lactate you can add should not be much, in fact 2.5 ml per cup (235 ml) of water are sufficient.

WARNING! Pay attention to calcium! It must be appropriately diluted. In case you have not done so, dilute the calcium in a bit of water (or milk) before adding it to your main ingredient.

3) Immerse the mixture in the bath of sodium alginate by using a spoon or a strainer: in this way a gelled film will form instantly on the surface, which becomes thicker towards the outside.

This is possible because the calcium goes out of the food and forms a gel with the sodium alginate in the bath (the reaction is explained IN THIS ARTICLE).

3 minutes are sufficient to obtain quite strong spheres.
Obviously, if the spheres remain for long time in the bath of sodium alginate, the gel will be thicker so you have to check constantly the immersion time.

It is also important to rotate the spheres in the bath of sodium alginate to obtain a homogeneous gelation and especially to avoid that the spheres touch each other to prevent them from sticking.

4) In the last step you have to wash the spheres well to get a smooth and flawless surface.
Moreover, as opposed to what happens in Spherification, the reverse Spherification process stops immediately by washing the spheres.
In this way you can create soft spheres with a liquid heart, stable over time (the nucleus is unstable over time in the Spherification).

Now let’s see how to make a tasty recipe thanks to reverse Spherification!

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Tzatziki maboul

Sphere of greek yogurt, cucumber

12 big spheres
20 minutes preparation
45 minutes of rest
2 hours in the freezer

Ingredients for the bath of sodium alginate
30 cl of water with low level of calcium (60mg / l)
1.5 g of sodium alginate

Ingredients for greek yogurt spheres
1 greek yogurt
1 large clove of garlic
Salt and pepper

Ingredients for the cucumber
1 cucumber
1 spoon of extra virgin olive oil
1 or 2 spoons of lemon juice
Coarse salt

METHOD FOR THE BATH OF SODIUM ALGINATE:

Pour the sodium alginate in the water with low level of calcium and stir with a whisk.
Mix your main food, avoid to incorporate too much air and let it rest at least 30 minutes.

FOR THE GREEK YOGURT BALLS:
Peel and grate the garlic. Then add it to yogurt. Then add salt and pepper and stir.
Filled the small hemispheric molds with yogurt and freeze them for at least 2 hours (this allows you to obtain homogeneous spheres)

You can prepare the spheres even without molds, by using a curved spoon and quickly dipping it in the bath of sodium alginate.

Dip the frozen spheres in the bath of sodium alginate for at least 30 seconds and avoid that they touch (we recommend to use a slotted spoon or strainer to better manipulate the spheres and obtain a better drip).

At last let defrost the spheres at room temperature.

THE CUCUMBER:
Peel the cucumber and remove the seeds. Cut it into very fine strips; add salt and let them rest for 15 minutes. Then wash them and squeeze them.

Add extra virgin olive oil and lemon juice.

HOW TO SERVE:
Serve every sphere of greek yogurt on a cucumber strip.
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TECHNICAL DETAILS:
The yogurt is perfect for its natural high level of calcium. When the yogurt mixture is immersed in the bath of sodium alginate, it will form instantly a gelled film on the surface that allows the revers Spherification.

After you remove the spheres from the bath of sodium alginate, the gelled film stops to grow.
Thanks to this amazing technique you can prepare soft spheres of yogurt with a liquid heart.

VARIATION:
You can replace the greek yogurt with another dairy product with high level of calcium (flavoured yogurt or fruit yogurt, fresh cheese, fresh cream, etc.).

Now you are able to realize the spheres with liquid hearts! You can add spices, chocolate chips, citrus peel, etc.

An original way to customize some classics preparations based on dairy products (Indian lassi, tandoori sauce, etc.).