All those good cooks here.. come come teach me....
How to prevent those leafy greens from turning yellow cos of lack
of oxygen huh??
Hey found this..
http://www.findarticles.com/p/articles/mi_m1216/is_n5_v188/ai_12252368
So--why do green vegetables change color when cooked?
At the first blast of heat, in hot water, steam, or fat, green
vegetables get brighter, but with longer cooking the green
fades.
What happens? Heat forces the gases surrounding the vegetable cells
to expand and escape. As a result, you can see the green pigment,
chlorophyll, more clearly. It's rather like fog fading away to let
light reveal the color.
Fried vegetables, as in tempura, cook so quickly they stay quite
green if eaten hot.
Boiled or steamed (including microwaved) vegetables like green
beans, peas, asparagus, broccoli, cabbage, and leafy greens are
ready to eat (tender to tender-crisp) while still brightly colored.
But if you want to serve vegetables cold or reheat them later, you
must stop their cooking with a shock to arrest color change. Drain
vegetables and at once immerse them in ice water until cool; this
stabilizes the chlorophyll. When reheated, the vegetables don't
fade as rapidly as when first cooked. (This is why frozen green
vegetables keep their color longer when cooked.)
Vegetables that take more cooking, like artichokes, lose their
bright color.
Why do green vegetables turn grayish yellow?
Heat is rough on chlorophyll, which is very unstable. One reason
recipes direct you to boil vegetables uncovered is so that
color-destructive gases surrounding the cells can dissipate
rapidly. If you cook vegetables in lots of boiling water, rather
than just a little, heat is distributed faster, and vegetables have
better color because there is less time for chlorophyll to fall
apart.
Green vegetable color fades to olive, then to grayish yellow, as
heat displaces the magnesium atoms in the chlorophyll, shifting its
chemical structure and the color.
Acid has the same visual effect on chlorophyll as heat does. But
another factor is at work. The acid's hydrogen atom replaces the
magnesium in chlorophyll, turning the color to a yellowish
graygreen. This is why green vegetables turn drab if they stand in
a tart dressing for more than a few minutes. To minimize the color
change, dress vegetables just before serving.
What do baking soda and copper pennies do to green
vegetables?
In the past, cooks often added baking soda or copper pennies to
cooking water because they made green vegetables stay brightly
colored.
Baking soda is alkaline (acid's opposite), and because it prevents
hydrogen from replacing magnesium in chlorophyll, the pigment gets
brighter. The negative: soda rapidly breaks down pectin that holds
cell walls together, making vegetables mushy.
Copper coins and unlined copper pans contain free copper or zinc
ions that also replace magnesium in chlorophyll, giving the green
color a bluish cast. The vegetable texture is not affected, but you
might be: eating too much copper sulfate can make you sick.
Why does red cabbage turn blue when cooked?
Red cabbage and other blue-red vegetables are a war zone for two
color pigments, anthocyanins (red) and betacyanins (blue). The red
color needs acid (lemon juice, vinegar) to anchor it; otherwise red
vegetables get the blues. For a little drama, cook red cabbage in a
little water. Then add acid to taste and cook further, watching the
unappetizing blue-purple color shift rapidly to red.
