Chemistry Of Cooking A Biochemist Explains The Chemistry Of Cooking

[kullatiro]

January 1, 2009 — A biochemist and
cook explains that cooking is all about
chemistry and knowing some facts
can help chefs understand why
recipes go wrong. Because cooking is
essentially a series of chemical
reactions, it is helpful to know some
basics. For example, plunging
asparagus into boiling water causes
the cells to pop and result in a
brighter green. Longer cooking,
however, causes the plant's cell walls
to shrink and releases an acid. This
turns the asparagus an unappetizing
shade of grey.


 You love to cook, but have you
whipped up some disasters? Even the
best recipes can sometimes go
terribly wrong. A nationally recognized
scientist and chef says knowing a little
chemistry could help.
Long before she was a cook, Shirley
Corriher was a biochemist. She says
science is the key to understanding
what goes right and wrong in the
kitchen.
"Cooking is chemistry," said Corriher.
"It's essentially chemical reactions."
This kind of chemistry happens when
you put chopped red cabbage into a
hot pan. Heat breaks down the red
anthocyanine pigment, changing it
from an acid to alkaline and causing
the color change. Add some vinegar
to increase the acidity, and the
cabbage is red again. Baking soda will
change it back to blue.
Cooking vegetables like asparagus
causes a different kind of reaction
when tiny air cells on the surface hit
boiling water.
"If we plunge them into boiling water,
we pop these cells, and they suddenly
become much brighter green,"
Corriher said.
Longer cooking is not so good. It
causes the plant's cell walls to shrink
and release acid.
"So as it starts gushing out of the
cells, and with acid in the water, it
turns cooked green vegetables into [a]
yucky army drab," Corriher said.
And that pretty fruit bowl on your
counter? "Literally, overnight you can
go from [a] nice green banana to an
overripe banana," Corriher said.
The culprit here is ethylene gas. Given
off by apples and even the bananas
themselves, it can ruin your perfect
fruit bowl -- but put an apple in a
paper bag with an unripe avocado,
and ethylene gas will work for you
overnight.
"We use this as a quick way to ripen,"
Corriher said. Corriher says
understanding a little chemistry can
help any cook.
"You may still mess up, but you know
why," she said. When it works, this
kind of chemistry can be downright
delicious.
WHAT ARE ACIDS AND BASES? An acid
is defined as a solution with more
positive hydrogen ions than negative
hydroxyl ions, which are made of one
atom of oxygen and one of hydrogen.
Acidity and basicity are measured on
a scale called the pH scale. The value
of freshly distilled water is seven,
which indicates a neutral solution. A
value of less than seven indicates an
acid, and a value of more than seven
indicates a base. Common acids
include lemon juice and coffee, while
common bases include ammonia and
bleach.
WHY DOES FOOD SPOIL? Processing
and improper storage practices can
expose food items to heat or oxygen,
which causes deterioration. In ancient
times, salt was used to cure meats
and fish to preserve them longer,
while sugar was added to fruits to
prevent spoilage. Certain herbs, spices
and vinegar can also be used as
preservatives, along with anti-
oxidants, most notably Vitamins C and
E. In processed foods, certain FDA-
approved chemical additives also help
extend shelf life.


http://www.sciencedaily.com/videos/2009/0112-chemistry_of_cooking.htm