18 April 2020 | New Scientist | 51EKATER
IN
A^ KHABIEVA/ALAMYThe back pages
I DON’T know what it is like for
you, but in my neighbourhood
it has been hard to buy eggs since
The Event, so I have been searching
for substitutes to use in baking.
Eggs have several important
roles in baked foods. They bind
ingredients, contribute moisture
and trap bubbles, helping to create
light textures. Vegan bakers and
those with egg allergies have
found a range of alternatives
to fulfil these functions.
Perhaps surprisingly, most of
these aren’t rich in fat and protein
like eggs, but consist principally
of carbohydrates – specifically
polysaccharides, which are chains
of sugar molecules. These can link
together to form networks, just
like the structures formed by
broken-down egg proteins.
Chia seeds and flax seeds are
among the most common vegan
egg substitutes. Polysaccharides
in the seed coat form a gummy gel
when mixed with water, which
binds mixtures and traps water.
Starchy fruits and vegetables
can also work well. Try swapping
eggs for mashed banana when
making pancakes, for instance.
Egg whites have a rare ability to
form stable foams – important for
making meringues, soufflés and
other airy desserts. When egg
whites are beaten, the physical
stress makes globular proteins
unfold and bond together,
reinforcing bubbles in the liquid.
One crucial protein, ovalbumin, is
relatively immune to beating, but
when subjected to heat, it unfolds
and coagulates, giving permanent
stability to the cooked foam.A few years ago, someone
discovered a substitute: the liquid
found in tins of beans, dubbed
aquafaba. Almost any beans seem
to work, but chickpea liquid has
a less beany taste than others.
During cooking, soluble
carbohydrates and proteins
diffuse out of the beans. There
has been little research into
which ones are responsible for
the liquid’s foaming properties,
but saponins may be important.
These sugar-derived molecules
have water-attracting and water-
repelling parts – just like egg white
proteins – which may collect at
bubble walls and stabilise bubbles.
Egg foams can break if the
proteins bind together too tightly
and squeeze out water, and thesame can happen with aquafaba.
A little acid, in the form of lemon
juice or cream of tartar, helps
to stabilise them. The hydrogen
ions in the acid stop proteins
from shedding their own
hydrogens and forming strong
sulphur-sulphur bonds.
To make aquafaba meringues,
line a baking tray with greaseproof
paper. Take the liquid from a
400-gram tin of chickpeas, add
a tablespoon of lemon juice
and whisk until very stiff. One
spoonful at a time, whisk in
125 grams of sugar. Place spoonfuls
of meringue on the baking tray.
Bake at 110°C for 90 minutes, then
turn the oven off but leave the
meringues inside until cool. Serve
with coconut yogurt and fruit. ❚You don’t need eggs to make meringues, just an understanding
of what they bring to the party, explains Sam WongPuzzles
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Follow him @samwong1Science of cooking Week 16
Baking without eggs
Science of cooking online
All projects are posted at
newscientist.com/cooking Email: [email protected]What you need
400g can of chickpeas
Lemon juice
Sugar
Next week
Dulce de leche: a supremely
comforting sugar and
milk confection