New Scientist - USA (2022-03-19)

19 March 2022 | New Scientist | 51

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These articles are

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What you need
250 millilitres of mango juice
5 grams of calcium lactate
5 grams of sodium alginate
1 litre of water
Blender or hand mixer
Hemisphere-shaped
tablespoon measure

IF YOU eat at fancy places, you may

have encountered orbs of sauce

or puree, held inside a membrane,

that burst in your mouth. Making

them involves a little chemistry,

but it can be done at home.

Now a staple of modernist

cuisine, the spherification

technique was patented in 1942 by

food scientist William Peschardt

and later popularised by chef

Ferran Adrià at El Bulli restaurant

in north-east Spain in the 2000s.

To try it, you need two special

ingredients that can be ordered

online. One is a salt called sodium

alginate, which comes from brown

algae. Alginate is formed of

polymers made of chains of sugar

molecules with negative charges.

These polymers can link together

to form a gel, but to do that, they

need help from ions with a double

positive charge. Sodium ions

have a single positive charge,

so they stick to the negative parts

of the alginate, but can’t pull two

polymers together.

The second ingredient is

calcium lactate, another salt,

this time containing calcium

ions. Their double positive

charge means they can attract

two alginate polymers at the same

time, forming the cross links we

need to turn the liquid into a gel.

The original spherification

method involves dissolving the

sodium alginate in the flavoured

liquid, then immersing drops

or spoonfuls into a solution of

calcium lactate. A gel skin should

quickly form on the outside,

trapping the liquid in the sphere.

My attempt to do this with

A hallmark of top-tier modernist cuisine, spherification is

nevertheless a technique you can try at home, says Sam Wong

The science of cooking

Conquer your spheres

mango juice hit a problem: when

I mixed in the sodium alginate,

it instantly formed a gel. Mangoes

contain little calcium, but perhaps

another mineral was causing the

problem. This method can also

fail if the liquid is too acidic.

Luckily, there is an alternative

technique: reverse spherification.

Here, calcium lactate is mixed

with the flavoured liquid, which is

dropped into a solution of sodium

alginate. This results in a thicker

membrane, but it should work

with almost any edible liquid.

If you live somewhere with hard

water, like London, your tap water

could turn to jelly on contact with

the alginate, so use bottled water

for the alginate bath if you have to.

Sodium alginate dissolves

poorly, so create your solution

with a blender or hand mixer, then

let it sit so any air bubbles escape.
To make mango spheres,
dissolve the calcium lactate in the
mango juice. Fill a hemisphere-
shaped tablespoon measure and
tip it into the alginate bath. Use a
spoon to rotate the sphere as the
gel sets. After 1 minute, take it out
of the alginate bath with a strainer
and put it into a water bath.
You can also use a pipette,
syringe or squeezy bottle to make
small drops that form caviar-like
spheres, but this is trickier because
the spheres tend to stick together.
The membrane is permeable, so
if you want to make the spheres in
advance, store them in mango juice
The science of cooking so the flavour doesn’t escape. ❚
appears every four weeks

Next week
Stargazing at home

Sam Wong is assistant news
editor and self-appointed
chief gourmand at
New Scientist. Follow
him @ samwong1

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