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The Pantry:
EGGS - THE
SCIENCE OF BAKING AND COOKING EGGS
Pantry: Eggs 101 |
  Eggs
are the backbone of many baked goods and contribute to its structure.
Eggs also provide steam for leavening or moisture for starch. Egg
yolks add moisturizing fat and helps emulsify the batter, giving the
baked good a smooth and creamy texture. The egg whites act as
strengtheners. There are
substitutes for fresh eggs, but they do alter the recipe.
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THE
SCIENCE OF BAKING AND COOKING
EGGS:
 Time
the baking of a custard carefully. Too short a time and the
custard will not set; too long and it will curdle.
When starch is present, the denatured egg
(unwound) proteins do not join together. This prolongs the temperature at
which the eggs coagulate, helping to prevent overcooking.
The way it works: It is thought that the
starch's molecules expand and "blocks" the egg's proteins from joining
together until a higher temperature is reached.. When the mixture gets hot
enough, somewhere around boiling (212 degrees F), everything joins together
- starch to egg protein, egg protein to egg protein, etc.
Custard without Starch (flour,
cornstarch) - thickens at 160 degrees F and curdles at 180
degrees F.
Custard with Starch -
thickens at close to boiling, at around 212 degrees F |
Eggs are primarily made up of
protein, so in order to understand how to cook eggs properly, it helps to
understand a little something about protein coagulation. The egg boasts all of
the essential amino acids: histidine, isoleucine, leucine, lysine, methionine,
phenylalanine, threonine, trypto0phan and valine. They are present in a pattern
that matches very closely the pattern the body needs, so the egg is often the
measuring stick by which other protein foods are measured.
Coagulation simply means the process
by which something – an egg, in this case – changes from a fluid into a
thickened mass. Here's how it works:
Protein molecules are made up of
many strands. When an egg is raw, these protein strands are bound to each other
in discrete little bundles, kind of like those nests of angel hair pasta you see
in the store. Because these bundles are separate from each other they allow
light to pass between them, which is why egg whites are transparent when raw.
Coagulation:
When eggs are heated, the protein in the white and yolk starts to coagulate.
This means that the liquid egg becomes firmer. As heating continues the egg
eventually becomes solid.
Eggs coagulate at
(as measured with an Instant Read Thermometer):
 | Whites: 140 degrees F
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| Yolks: 150 degrees F |
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When heat is applied to these
proteins, they being to unwind and become unstuck from one another. As they do
so, the bonds that previously stuck them to one another began to waver around
freely, and as the now-loosened protein strands run into each other they again
stick to each other, but in this case they form not a tight little bundle but a
kind of a web similar to a spider web. This web is dense enough to prevent light
from passing through, which is why cooked eggs whites are white in color. The
web also traps moisture, which is why eggs cooked to just this point are moist
and tender.
If you keep cooking the eggs too
long, though, the protein strands once again become unstuck from each other, the
web dissolves, and all the moisture comes flowing out. That’s why, for example,
if you cook a custard (which is thickened by eggs) too long, you reach a point
where the custard "breaks" and gives off liquid.
So the idea is to cook the eggs just
long enough to make them tender and solid, but not so long that they lose their
moisture and become tough.
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Safe cooking times for eggs: |
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Method |
Time |
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Scrambled |
1 minute or more |
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Sunnyside
up |
5 minutes |
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Over easy |
3 minutes first side;
2 minutes second side |
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Poached |
5 minutes |
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Boiled |
7 minutes |
Cooking Tips: The basic principle of egg
cooking is to use a medium to low temperature and time carefully.
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To
get fluffy scrambled eggs: whisk the eggs with 1 teaspoon water
per egg instead of milk. Cook with a little bit of butter in the pan on low
heat. They turn out perfect every time. |
Egg white proteins coagulate first
at about 140 degrees F, with the white no longer flowing near 149 degrees F. It
becomes opaque and forms a gel. Heating the egg white much beyond this
temperature shrinks and toughens the coagulation of the white. Coagulation of
the yolk begins near 150 - 151 degrees F, and the yolk thickens and no longer
flows when the temperature nears 158 - 160 degrees F.
When eggs are cooked at too high a
temperature or for too long at a low temperature, whites shrink and become tough
and rubbery; yolks become tough and their surface may turn gray-green. Eggs,
other than hard-cooked, should be cooked until the whites are completely
coagulated and the yolks begin to thicken.
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Wouldn't it be nice to hard boil eggs and have the yolk part centered in the
middle of the white?
Here's how you do it: 24 hours before boiling, set the carton on its side
with the raw eggs nestled inside. Then, cook the eggs after that. The yolk
should appear in the middle of the white. |
Hard Boiled
Eggs Tips: I put however many eggs I want to cook into a pot of cold
water. I bring it to a boil, I cover the pan, I remove the pan from the heat,
and I wait eight minutes. Peel immediately under cold running water. That will
give you a slightly soft yolk. If you want a really hard yolk, go with twelve
minutes.
The fresher that the eggs used in
hard cooked ones are, the harder they are to peel. They become less so as they
age and will peel more easily. Eggs a week or 10 days old should peel easily.
To add multiple eggs one at a
time to a recipe, there are several ways to pre-crack them:
| If cracked and placed in a
plastic bag to warm (see above), pour them individually and directly from
it to the recipe; or, |
| Individually place cracked
eggs in a paper muffin liner. This way they can be added to the recipe one
at a time. After using, simply throw the liner away; or,
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| Another way is to crack
all of the eggs into a large, glass measuring cup. You can then pour them
into the mixing bowl, one at a time while mixing.
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from Shirley Corriher's CookWise
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