WITH EGG WHITES
week I wanted to explain a little about the whys and
wherefores of working with egg whites. A little bit
of science in the kitchen folowed by an example recipe
where you need to bear in mind what I am about to explain.
do egg whites foam?
If you try to whip plain water into a foam, you won't
have much luck. Bubbles that form in plain water quickly
pop. That's because water molecules stick together.
Water molecules are electrically attracted to each other.
They won't spread out to form a bubble film unless you
add something that lessens the attraction.
egg white is about 90% water and 10% protein. The egg-white
proteins are long chains of amino acids that fold and
curl into more or less spherical tangles. When you beat
an egg white, these proteins uncurl and stretch out.
the proteins uncurl, they expose amino acids that were
hidden in the centre of the tangle. Some of the amino
acids repel water; these are hydrophobic, or water-fearing
amino acids. Some of the amino acids are electrically
charged and are attracted to water; these are hydrophilic,
or water-loving amino acids.
you beat the egg whites, you also whip bubbles into
the mixture. The water molecules and egg-white proteins
bump around, jockeying for position. The water molecules
are attracted to each other and to the hydrophilic amino
acids on the proteins. While trying to get close to
each other and to the hydrophilic amino acids, the water
molecules squeeze the hydrophobic amino acids out. The
best place for the egg proteins is on the surface of
the liquid, with their hydrophobic amino acids sticking
out into the air.
surface of each bubble film becomes crowded with egg
proteins. The water molecules are forced apart by these
proteins. Since the attraction between water molecules
decreases with distance, the water molecules don't stick
together quite as well-they can spread out and make
a bubble film.
the water molecules so that they spread out in bubble
films is only one step in making a meringue. The chicken
egg contains a mixture of proteins that makes meringue
possible. Some of the proteins form bonds with each
other to create a stable network that keeps the bubbles
from popping. When the meringue is in the oven, another
protein-ovoalbumin-forms bonds that cause the meringue
Egg whites at room temperature can be beaten to a foam
more easily than cold egg whites.
can't I use a plastic bowl?
Fat interferes with the formation of a good foam-and
fat clings to plastic. No matter how carefully you clean
a plastic bowl, odds are good that a bit of grease remains
behind. It's preferable - and easier - to use a glass
or stainless steel bowl to produce a fluffy meringue.
Egg yolks also contain fat, so when you separate the
eggs, try to make sure that none of the yolk ends up
in your egg whites.
not add sugar at the beginning?
Adding sugar at the beginning can double the time you
have to whip the egg whites to get a foam. That's because
the sugar molecules get in the way of the egg proteins.
With sugar molecules in the way, it takes longer for
the proteins to find each other and form bonds.
When meringue is cooking, sugar helps keep it stable
by bonding with water molecules and preventing them
from escaping as water vapour. Delaying the evaporation
of water from the foam helps keep the foam stable until
Adding vinegar (or any other acid) can make the foam
less likely to suffer the consequences of over beating:
lumpiness, loss of water, and collapse. These undesirable
consequences result from too many bonds forming between
the egg proteins.
you add an acid to a mixture, you are essentially adding
some positively charged particles. These positively
charged particles are hydrogen ions-hydrogen atoms that
have lost an electron. The hydrogen ions hop onto charged
portions of the proteins and leave them uncharged. Proteins
that are electrically neutral are less likely to react
with other proteins.
The Pavlova recipe is a good illustration of these
whites (room temp)
vinegar or lemon juice
the egg whites and sugar in a stainless steel bowl
over a bain-marie (double boiler)
the whites and sugar together until it reaches a temperature
of 40ºC (it will feel just warm to the touch
if you do not have a food thermometer)
it from the bain-marie and continue beating it until
it is completely cold
the mixture is cold fold in the sifted corn flour
and the vinegar
the vanilla essence to taste (approx. 2 tsp)
a large, deep bottomless cake ring onto a baking sheet
lined with greaseproof paper or a silicon mat, spoon
in the mixture and level it off with a palette knife
a knife around the inside of the cake ring to remove
it and tidy the edges with a palette knife
mixture onto silicon mat (or baking sheet lined with
greaseproof paper) and shape free form with a warm,
wet palette knife
in a warm oven 160°C just until the Pavlova starts
to crack with little or no colour
from the oven and allow to cool
with whipped cream and fresh fruits or make it part
of a larger dessert
large one or smaller individual ones may be formed
taller / thicker the Pavlova the better, as this ensures
a creamier centre - about 15cm tall is ideal.
can also be had by making as per meringue (without
the use of a bain marie) but the result is more of
a meringue texture than a soft marshmallow inner).
are best stored at room temperature, chilling them
will cause the sugar to sweat out of them.
and bon appetit . . . . .
quantity (add to taste)
meaning a whole one of
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