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The Color of Meat and Poultry
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I've just opened a
package of fresh chicken and the skin looks blue. Is it safe
to use?
My package of ground beef is dark in the center. Is
this old meat?
The turkey was cooked according to the directions,
but the breast meat is pink. Will it make us sick?
These are just a few of the many questions received at the U.S.
Department of Agriculture's Meat and Poultry Hotline concerning
the color of meat and poultry. Color is important when meat
and poultry are purchased, stored, and cooked. Often an attractive,
bright color is a consideration for the purchase. So, why are
there differences in the color and what do they mean? Listed
below are some questions and answers to help you understand
the color differences.
1. What factors affect the color of meat and poultry?
Myoglobin, a protein, is responsible for the majority
of the red color. Myoglobin doesn't circulate in the blood but
is fixed in the tissue cells and is purplish in color. When
it is mixed with oxygen, it becomes oxymyoglobin and produces
a bright red color. The remaining color comes from the hemoglobin
which occurs mainly in the circulating blood, but a small amount
can be found in the tissues after slaughter.
Color is also influenced by the age of the animal, the species,
sex, diet, and even the exercise it gets. The meat from older
animals will be darker in color because the myoglobin level
increases with age. Exercised muscles are always darker in color,
which means the same animal can have variations of color in
its muscles.
In addition, the color of meat and poultry can change as it
is being stored at retail and in the home (see explanation in
question 5). When safely stored in the refrigerator
or freezer, color changes are normal for fresh meat and poultry.
2. Does a change in color indicate
spoilage?
Change in color alone does not mean the product is spoiled.
Color changes are normal for fresh product. With spoilage there
can be a change in color—often a fading or darkening.
In addition to the color change, the meat or poultry will have
an off odor, be sticky or tacky to the touch, or it may be slimy.
If meat has developed these characteristics, it should not be
used.
3. If the color of meat and poultry changes while
frozen, is it safe?
Color changes, while meat and poultry are frozen, occur just
as they do in the refrigerator. Fading and darkening, for example,
do not affect their safety. These changes are minimized by using
freezer-type wrapping and by expelling as much air as possible
from the package.
4. What are the white dried patches on frozen meat
and poultry?
The white dried patches indicate freezer burn. When meat and
poultry have been frozen for an extended period of time or have
not been wrapped and sealed properly, this will occur. The product
remains safe to eat, but the areas with freezer burn will be
dried out and tasteless and can be trimmed away if desired.
THE COLOR OF MEAT
5. When displayed at the
grocery store, why is some meat bright red and other meat very
dark in color?
Optimum surface color of fresh meat (i.e., cherry-red for beef;
dark cherry-red for lamb; grayish-pink for pork; and pale pink
for veal) is highly unstable and short-lived. When meat is fresh
and protected from contact with air (such as in vacuum packages),
it has the purple-red color that comes from myoglobin, one of
the two key pigments responsible for the color of meat. When
exposed to air, myoglobin forms the pigment, oxymyoglobin, which
gives meat a pleasingly cherry-red color. The use of a plastic
wrap that allows oxygen to pass through it helps ensure that
the cut meats will retain this bright red color. However, exposure
to store lighting as well as the continued contact of myoglobin
and oxymyoglobin with oxygen leads to the formation of metmyoglobin,
a pigment that turns meat brownish-red. This color change alone
does not mean the product is spoiled (see explanation in question
2).
6. Why is pre-packaged ground beef red on the outside
and sometimes grayish-brown on the inside?
These color differences do not indicate that the meat is spoiled
or old. As discussed earlier, fresh cut meat is purplish in
color. Oxygen from the air reacts with meat pigments to form
a bright red color which is usually seen on the surface of ground
beef purchased in the supermarket. The interior of the meat
may be grayish-brown due to the lack of oxygen penetrating below
the surface.
7. A beef roast has darkened in the refrigerator,
is it safe?
Yes, it is safe. The darkening is due to oxidation, the chemical
changes in myoglobin due to the oxygen content. This is a normal
change during refrigerator storage.
8. Can cooked ground beef still be pink inside?
Yes, ground beef can be pink inside after it is safely cooked.
The pink color can be due to a reaction between the oven heat
and myoglobin, which causes a red or pink color. It can also
occur when vegetables containing nitrites are cooked along with
the meat. Because doneness and safety cannot be judged by color,
it is very important to use a food thermometer when cooking
ground beef. To be sure all harmful bacteria are destroyed,
cook all ground beef products to an internal temperature of
160 °F throughout.
9. What causes iridescent colors on meats?
Meat contains iron, fat, and other compounds. When light hits
a slice of meat, it splits into colors like a rainbow. There
are various pigments in meat compounds that can give it an iridescent
or greenish cast when exposed to heat and processing. Wrapping
the meat in airtight packages and storing it away from light
will help prevent this situation. Iridescence does not represent
decreased quality or safety of the meat.
10. What causes grayish or green color on cured
meats?
Exposure to light and oxygen causes oxidation to take place,
which causes the breaking down of color pigments formed during
the curing process. Chemicals in the cure and oxygen, as well
as energy from ultraviolet and visible light, contribute to
both the chemical breakdown and microbial spoilage of the product.
Cure, such as nitrite, chemically changes the color of muscle.
Curing solutions are colored in order to distinguish them from
other ingredients (such as sugar or salt) used in fresh and
cured meat products. For example, cured raw pork is gray, but
cured cooked pork (e.g., ham) is light pink.
THE COLOR OF POULTRY
11. What is the usual color of raw poultry?
Raw poultry can vary from a bluish-white to yellow. All of these
colors are normal and are a direct result of breed, exercise,
age, and/or diet. Younger poultry has less fat under the skin,
which can cause the bluish cast, and the yellow skin could be
a result of marigolds in the feed.
12. What causes the differences in color of raw
ground poultry?
Ground poultry varies in color according to the part being ground.
Darker pink means more dark meat was used and a lighter pink
means more white meat was included (or skin was included). Ground
poultry can contain only muscle meat and skin with attached
fat in proportion to the whole bird.
13. What causes dark bones in cooked poultry?
Darkening of bones and meat around the bones occurs primarily
in young (6-8 weeks) broiler-fryer chickens. Since the bones
have not calcified or hardened completely, pigment from the
bone marrow seeps through the bones and into the surrounding
area. Freezing can also contribute to this darkening. This is
an aesthetic issue and not a safety one. The meat is safe to
eat when all parts have reached at least 165 °F.
14. What color is safely cooked poultry?
Safely cooked poultry can vary in color from white to pink to
tan. For safety when cooking poultry, use a food thermometer
to check the internal temperature. Poultry should reach a safe
minimum internal temperature of 165 °F throughout the product.
For a whole chicken or turkey, check the internal temperature
in the innermost part of the thigh and wing and the thickest
part of the breast. All the meat-including any that remains
pink—is safe to eat as soon as all parts reach at least 165
°F.
15. Why is some cooked poultry pink?
Chemical changes occur during cooking. Oven gases in a heated
gas or electric oven react chemically with hemoglobin in the
meat tissues to give it a pink tinge. Often meat of younger
birds shows the most pink because their thinner skins permit
oven gases to reach the flesh. Older animals have a fat layer
under their skin, giving the flesh added protection from the
gases. Older poultry may be pink in spots where fat is absent
from the skin. Also, nitrates and nitrites, which are often
used as preservatives or may occur naturally in the feed or
water supply used, can cause a pink color.
16. If fully cooked smoked poultry is pink, is
it safe?
Poultry grilled or smoked outdoors can be pink, even when all
parts have attained temperatures well above 165 °F. There
may be a pink-colored rim about one-half inch wide around the
outside of the cooked product. Commercially prepared, smoked
poultry is usually pink because it is prepared with natural
smoke and liquid smoke flavor. |
Last Modified:
January 28, 2008 |
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