So-called spherification is based on a food re-engineering
manufacturing process. For years, the food industry has been
using this process to re-engineer fruit, vegetable or meat purees
into pieces whose form and texture are very similar to the basic
ingredient. For example, what appears to be a piece of bell pepper
stuffed into pitted olives is actually a gelled and remolded puree.
By doing so, the industry is able to maintain consistent uniformity
in the appearance of products. In addition, by using puree rather
than whole foods, the industry can achieve substantial cost savings.

One thing is for certain: when Catalan chef Ferran Adrià of the
famous restaurant El Bulli in Spain adopted and perfected this
technique, he had something else in mind other than recycling raw
material! In molecular gastronomy, spherification is now defined
as the encapsulation of a liquid inside different sized spheres that
burst in the mouth.

The wall trapping the liquid inside the sphere consists of a gel formed
by a process similar in some respects to the one described in the
preceding section on gelling. The additive used is sodium alginate,
and just like in the gelling process using carrageenans or gellan
gum, the presence of ions is essential for the formation of the gel.
In the case of a sodium alginate gel, the presence of calcium ions
is required so that the long alginate molecules can align and bind
to finally form a gel. To better understand the ability of sodium
alginate to form a gel, let’s take a closer look at the molecule.

Alginate reacts with any calcium that naturally occurs or that
has been added to the ingredient to be spherified. For example,
we could make a pudding by simply adding sodium alginate to a
preparation of milk and sugar, as milk is naturally rich in calcium.
Applying this principle, we can precisely control the moment when
the calcium and alginate come into contact and thereby diversify
the liquids to be gelled and the forms obtained.

Depending on the source of calcium ions, two types of spherification
can be used:

01 BASIC SPHERIFICATION
02 REVERSE SPHERIFICATION

Both techniques can be used to create different sized spheres.
However, basic spherification is preferred to create small balls, or
caviar, whereas reverse spherification is the preferred method to
form larger spheres, also called flavor bubbles.

 

BASIC SPHERIFICATION

Basic spherification consists in immersing a liquid containing
sodium alginate in a high-calcium bath. Calcium ions then migrate
from the sphere’s exterior to its interior.

As a large amount of calcium ions remains present in the caviar’s
wall, even a water rinse will not completely slow down the gelling of
the wall, which will thicken until the sphere’s interior is completely
gelled. Since an in-the-mouth flavor burst is usually desired, it is
recommended to serve the caviar as quickly as possible after its
formation.

It is important to note that the addition of the sodium alginate
solution to the preparation to be transformed significantly dilutes
it. So, for maximum flavor, be sure to transform solutions that are
highly flavorful; otherwise the taste will be rather bland. Sodium
alginate will also thicken the preparation. Since the preparation
is thicker and less intense in flavor, basic spherification is not
recommended for creating large flavor bubbles. However, it is the
most practical technique to create small beads, commonly known
as flavor caviar.

REVERSE SPHERIFICATION

As its name suggests, compared with basic spherification, reverse
spherification involves a permutation in the process of immersing
sodium alginate and calcium salt. The principle is to pour a highcalcium
solution in a bath in which sodium alginate has been
dissolved. Calcium ions then migrate from the sphere’s interior
to its wall.

Unlike what happens in basic spherification, it is possible to slow
down the wall’s thickening process, since rinsing removes excess
sodium alginate on the sphere’s contours. In the absence of alginate
molecules, calcium ions have no effect and the sphere’s interior
remains liquid. Once rinsed, flavor bubbles can be stored and served
sometime after their formation.

Dissolving sodium alginate in a solution significantly thickens it. The
sodium alginate bath is therefore very thick and some solutions
that are too watery simply cannot penetrate it: the result will look
more like a deformed lump of gel than a sphere!

When choosing preparations to be spherified, it is best to work with
liquid bases that are naturally thick and high in calcium such as
cream, yogurt and certain purees. It is also possible to thicken the
preparation to be transformed using a thickening agent such as
xanthan gum to minimize the density gap with the sodium alginate
bath. However, to spherify very watery solutions, frozen reverse
spherification is recommended.

FROZEN REVERSE SPHERIFICATION

Freezing solutions enables greater precision in the final form and
overcomes many of the limitations and constraints of spherification.
The technique is straightforward and very similar to reverse
spherification.

A pinch of calcium salt is first added to the preparation to be
transformed, after which the preparation is molded and frozen. The
ice cubes thus produced are then immersed in a sodium alginate
bath and rinsed. You no longer have to worry about the preparation’s
texture, since the ice cubes easily penetrate the surface of the sodium
alginate bath. So you can transform completely liquid solutions for
an even more spectacular in-the-mouth effect!

OTHER CHARACTERISTICS

Sodium alginate-based gels are irreversible and therefore can be
served hot. To do this, simply immerse the spheres in hot water
and wait until the heat is absorbed. In addition, they are resistant to
freezing and thawing. The fact that they can congeal cold without
prior heating is also a certain advantage.

Nevertheless, it is important to note that the spherification process
may be hindered by a high level of acidity or alcohol. Frozen reverse
spherification avoids most of these contraindications, obviously
provided that the preparation can be frozen.

Finally, be wary of unknown calcium sources that could congeal
the preparation without warning. If the tap water is particularly
high in calcium, it would be preferable to use bottled water. Also,
do not pour the alginate bath down a narrow pipe; otherwise, it
could form a blockage!

Learn more about Sodium alginate and Calcium lactate.