Vegetables Color Problems When Cooking
Vegetables are such a vital part
of our diet, it is important to know how to prepare it correctly and as many
varieties as possible. After all, you need to keep eating your greens to keep
you healthy. Most people don't get nearly the recommended amount of vegetables
each day, but now lack of knowledge can't be your excuse!
Cooking changes a vegetable's texture, flavor, color, and
nutrient content. High temperatures make vegetables tender and enhance flavor.
In addition, cooking usually makes vegetables safer to eat by killing microbes.
Overcooking, however, will cause
texture, flavor, color, and nutrient content to deteriorate.
1)
The key to cooking vegetables is to make
the tissue tender without making it too soft. You can determine whether a
vegetable is done by testing a piece during cooking. Most vegetables should be
tender but still firm. Color can also indicate whether a vegetable is done. Green
vegetables are overcooked if they turn an olive green. Delicate leafy
vegetables require only a few minutes to cook, while stem and root vegetables
may require more time.
2) Quick cooking
and the least exposure to water or
other fluids are recommended.
3)
Acidic ingredients, such as citrus juice, tomatoes and vinegar, should be
withheld during the very last minutes to help avert color loss.
4)
The firm cellular structures of some vegetables are vulnerable to both heat and
acids. Raw green vegetables are less affected than cooked vegetables because
their protective cell walls have not been exposed to heat. If green vegetables
are cut into small pieces to
facilitate faster cooking, this may help retain the phytochemical chlorophyll.
5) Chlorophyll
is the source of their bright green color pigment present in all green
vegetables such as asparagus, green beans, broccoli,
peas, and spinach. Chlorophyll is destroyed by acids, such as lemon juice and
vinegar, and by baking soda. Prolonged cooking or overcooking causes bright
green vegetables to turn a drab olive green. Steaming is the most preferred
method for cooking because steam cooks food rapidly, lessens the loss of
nutrients and flavor, and does not break up delicate vegetables.
6)
Potatoes and onions may turn a brownish-yellow when cooked with alkaline ingredients, such as egg whites,
or in certain metal pots, such as aluminum
or iron. This reaction may be due to
the flavonoids in potatoes and onions, plant substances with antioxidant
properties. An acidic ingredient, such as cream of tartar, lemon juice or
vinegar, may be added to help neutralize the alkaline environment in which
these vegetables are cooked and prevent discoloration.
Flavones are the white
pigments found in potatoes, onions, cauliflower, and the white parts of
celery, cucumbers, and zucchini. Cook these vegetables for a short time to avoid
loss of nutrients, flavor, and color. Overcooking
and hard water turn white vegetables a dull yellow or gray.
7)
Acidic tomatoes, chili peppers and/or onions may also help to prevent avocadoes
from turning brown in guacamole. Other
colorful photochemicals, or plant compounds that undergo the
effects of cooking, include anthocyanins,
betalains and
carotenoids:
8) Carotenoids
are the yellow and orange pigments found in carrots, corn, sweet potatoes,
tomatoes, and winter squash. These pigments are very stable to acids and heat,
but loss of color, nutrients, and flavor occurs with overcooking.
9) Anthocyanins,
found in ruddy cherries, red and purple grapes, red cabbage,
walnuts and wine, tend to lose their color rapidly during cooking. Like bright
green vegetables with chlorophyll, fruits and vegetables with anthocyanins
should be quickly cooked with little
exposure to water or other fluids.
Anthocyanins are the red
pigments found only in a few vegetables, such as beets and red cabbage.
These red pigments react very strongly to acids and alkalis. Acids make
anthocyanins brighter red, and alkalis turn them a blue or blue-green color. So
a small amount of acid gives red beets and red cabbage a bright red color. This
is why red cabbage is often cooked with tart
apples. Because acids toughen vegetables and prolong cooking time, in
recipes that call for lemon juice, tomatoes, or other acids, add only a small amount at the beginning of
cooking and the remaining toward the end after the vegetables have become
tender. Since anthocyanins dissolve easily in water, cook these vegetables
quickly in as little water as needed.
10)
Red cabbage loses its color and turns green in some sauces because of two
chemical reactions: one that produces a blue pigment and one that produces a
yellow pigment. When these two pigments combine, they produce a blue-green
color. To prevent this reaction, a little acidic
lemon juice or vinegar may be added to the cabbage. Likewise, a little
acidic buttermilk or yogurt may be added to cherries or
walnuts during baking to help prevent their discoloration.
11) Betalains,
found in purple-red beets, rapidly stain other ingredients. To prevent
staining, once beets are cooked, they should be carefully dried and added last
to other ingredients. If beets are marinated in an acidic ingredient, such as
lemon juice or vinegar, it may darken their color.
The reverse is true with grapes: the longer grapes are immersed
in a sauce or dressing, the greater the chance that they will lose their color.
12) Carotenoids,
found in brightly colored orange and red fruits and vegetables, such as
carrots, tomatoes, pumpkins and sweet potatoes, generally retain their color
unless they are overcooked.
Basic Cooking Methods to Prevent Color
Changes in Vegetables
General Procedures:
1) Use as little water as possible, with the exception of strong-flavored
vegetables like cabbage.
2) Cover yellow, orange, and red vegetables. Do not cover green and white
vegetables.
3) Cook vegetables as quickly as possible to soften fibers and
retain nutrients, color, and flavor.
4) Drain vegetables, but save
the cooking water because it contains nutrients and flavor. Use the water
in soups, sauces, and gravies.
5) Season vegetables before serving. Use salt and high-fat sauces
and butter sparingly.
6) You should stop cooking vegetables when they become tender.
Desired tenderness varies depending on the vegetable. Winter squash, eggplant,
and similar vegetables are properly cooked when they turn soft, but most
vegetables are best when cooked very briefly or until they are crisp tender. At
this stage vegetables maintain their maximum flavor, color, and nutrients.
Using Microwave
Oven to Cook Vegetables
1) Vegetables cook quickly and easily in the microwave oven.
Only a few tablespoons of water are needed and microwaving preserves the
nutrients, color, and texture of most vegetables. Always cover vegetables in the microwave. To microwave vegetables:
2) Place evenly cut vegetables in a ceramic dish. Add 2 tablespoons
of water to fresh vegetables. Frozen
vegetables usually require no extra water.
3) Cover the vegetables and cook on high until fork tender. Halfway
through the cooking cycle, stir the vegetables.
Steaming is a
Good and Healthy Option
1) This method can be used for both pressurized steam cookers
and range-top steamers which contain a perforated basket over a pot of boiling
water. Pressurized steamers are not
recommended because it is too easy to overcook the vegetables.
2) If you use a pressurized steam cooker, follow the manufacturer's
instructions. For range-top cooking, bring 1 to 2 inches of water to a boil in
a saucepan.
3) Arrange vegetables in shallow, even layers in a perforated
pan or basket for cooking.
4) Insert pan or basket into steamer or saucepan and cook until
fork tender for most vegetables. Follow guidelines for preserving color,
texture, and nutrients.
5) Use 2-Tiered 6-quart capacity steamer that creates instant
steam for preparing all kinds of food like Oster
Food Steamer.
In summary, heat may cause bright green vegetables to lose
their color during cooking. In
order to preserve the color of vegetables, it is better to shorten the cooking time; use
tap water, which is a little alkaline; plunge
the vegetables into ice water to halt the cooking process and then reheat
briefly; or add a little protective
seal of fat or oil right after cooking. This may be a bit of olive oil or
butter. The use of an acidic ingredient in a sauce or dressing should be withheld until the very last minute,
since the acid may further break down the cell walls. To make your cooking
easier use the recommended cooking times below:
Recommended
Cooking Times for Common Vegetables
|
Vegetable
|
Steam
|
Microwave
|
Blanch
|
Boil
|
Other
|
|
Artichoke, whole
|
30 to 60
|
4 to 5 each
|
not
recommended
|
25 to 40
|
not
recommended
|
|
Artichoke, hearts
|
10 to 15
|
6 to 7
|
8 to 12
|
10 to 15
|
Stir-fry 10
|
|
Asparagus
|
8 to 10
|
4 to 6
|
2 to 3
|
5 to 12
|
Stir-fry pieces 5
|
|
Beans, green
|
5 to 15
|
6 to 12
|
4 to 5
|
10 to 20
|
Stir-fry 3 to 4
|
|
Beans, lima
|
10 to 20
|
8 to 12
|
5 to 10
|
20 to 30
|
not
recommended
|
|
Beets
|
40 to 60
|
14 to 18
|
not
recommended
|
30 to 60
|
Bake 60 at 350°F
|
|
Broccoli, spears
|
8 to 15
|
6 to 7
|
3 to 4
|
5 to 10
|
Blanch, then bake
|
|
Broccoli, flowerets
|
5 to 6
|
4 to 5
|
2 to 3
|
4 to 5
|
Stir-fry 3 to 4
|
|
Brussels sprouts
|
6 to 12
|
7 to 8
|
4 to 5
|
5 to 10
|
Halve; stir-fry 3 to 4
|
|
Cabbage, wedges
|
6 to 9
|
10 to 12
|
not
recommended
|
10 to 15
|
Blanch leaves, stuff and bake
|
|
Cabbage, shredded
|
5 to 8
|
8 to 10
|
not
recommended
|
5 to 10
|
Stir-fry 3 to 4
|
|
Carrots, whole
|
10 to 15
|
8 to 10
|
4 to 5
|
15 to 20
|
Bake 30 to 40 at 350°F
|
|
Carrots, sliced
|
4 to 5
|
4 to 7
|
3 to 4
|
5 to 10
|
Stir-fry 3 to 4
|
|
Cauliflower, whole
|
15 to 20
|
6 to 7
|
4 to 5
|
10 to 15
|
Blanch, then back 20 at 350°F
|
|
Cauliflower, florets
|
6 to 10
|
3 to 4
|
3 to 4
|
5 to 8
|
Stir-fry 3 to 4
|
|
Corn, on cob
|
6 to 10
|
3 to 4
|
3 to 4
|
4 to 7
|
Soak 10; bake at 375°F
|
|
Corn, cut
|
4 to 6
|
2 per cup
|
2 1/2 to 4
|
3 to 4
|
Stir-fry 3 to 4
|
|
Eggplant, whole
|
15 to 30
|
7 to 10
|
10 to 15
|
10 to 15
|
Bake 30 at 400
|
|
Eggplant, diced
|
5 to 6
|
5 to 6
|
3 to 4
|
5 to 10
|
Bake 10 to 15 425°F
|
|
Greens, collard/mustard/turnip
|
not
recommended
|
18 to 20
|
8 to 15
|
30 to 60
|
Stir-fry mustard greens 4 to 6
|
|
Greens, kale/beet
|
4 to 6
|
8 to 10
|
4 to 5
|
5 to 8
|
Stir-fry 2 to 3
|
|
Kohlrabi
|
30 to 35
|
8 to 12
|
not
recommended
|
15 to 30
|
Bake 50 to 60 at 350°F
|
|
Mushrooms
|
4 to 5
|
3 to 4
|
not
recommended
|
3 to 4 in broth or wine
|
Stir-fry or broil 4 to 5
|
|
Onions, whole
|
20 to 25
|
6 to 10
|
not
recommended
|
20 to 30
|
Bake 60 at 400°F
|
|
Onions, pearl
|
15 to 20
|
5 to 7
|
2 to 3
|
10 to 20
|
Braise in broth 15 to 25
|
|
Parsnips
|
8 to 10
|
4 to 6
|
3 to 4
|
5 to 10
|
Bake 30 at 325°F
|
|
Peas
|
3 to 5
|
5 to 7
|
1 to 2
|
8 to 12
|
Stir-fry 2 to 3
|
|
Peppers, bell
|
2 to 4
|
2 to 4
|
2 to 3
|
4 to 5
|
Stir-fry 2 to 3
|
|
Potatoes, whole
|
12 to 30
|
6 to 8
|
not
recommended
|
20 to 30
|
Bake 40 to 60 at 400°F
|
|
Potatoes, cut
|
10 to 12
|
8 to 10
|
not
recommended
|
15 to 20
|
Bake 25 to 30 at 400°F
|
|
Spinach
|
5 to 6
|
3 to 4
|
2 to 3
|
2 to 5
|
Stir-fry 3
|
|
Squash, sliced
|
5 to 10
|
3 to 6
|
2 to 3
|
5 to 10
|
not
recommended
|
|
Squash, halves
|
15 to 40
|
6 to 10
|
not
recommended
|
5 to 10
|
Bake 40 to 60 at 375°F
|
|
Squash, whole
|
not recommended
|
5 to 6
|
not
recommended
|
20 to 30
|
Bake 40 to 90 at 350°F
|
|
Tomatoes
|
2 to 3
|
3 to 4
|
1 to 2
|
not
recommended
|
Bake halves 8 to 15 at 400
|
|
Turnips, whole
|
20 to 25
|
9 to 12
|
not
recommended
|
15 to 20
|
Bake 30 to 45 at 350°F
|
|
Turnips, cubed
|
12 to 15
|
6 to 8
|
2 to 3
|
5 to 8
|
Stir-fry 2 to 3
|
|
Zucchini
|
5 to 10
|
3 to 6
|
2 to 3
|
5 to 10
|
Broil halves 5
|
Try your newly acquired knowledge at this
recipe:
Keep yourself healthy
and happy cooking! :-)
