Meat+Poultry - December 2019 - 76

M E AT P E R S P E C T I V E S

Consumers are looking
for a certain color when
they are purchasing
ground beef, whether it's
packaged or sold fresh.

oxygen present, the
myoglobin pigment is
in the deoxymyoglobin
state, and when there
is atmospheric oxygen
present, the pigment
is in the oxymyoglobin
state. When there are
low partial pressures
of oxygen present - too
much for the formation of
deoxymyoglobin and too
little for oxymyoglobin to
form - the iron in myoglobin
will oxidize and the brown
pigment, metmyoglobin, will
appear. This transition is easy
to observe when beef steaks
are first vacuum packaged where
they may be initially red, followed
by the development of the brown color, and
ultimately, they become purple in color. The
type of muscle, its postmortem age, and even
quality grade may impact the transition from
purple to red with a stop through brown. If
steaks are frozen when they are in this brown
stage, the steaks are likely to remain there
making them less appealing to most customers.

BROWN INTERIOR
Why is the interior of the meat brown in color
when the exterior is red? This is a very common concern by purchasers of fluff-packaged
PVC-overwrapped ground beef. Many of these
calls/emails over the years have focused on
the thought that unscrupulous retailers have
taken fresh ground beef and layered it over
the old ground beef, so that consumers would
be tricked into purchasing old product. This
is definitely not the case. The answer to this
phenomenon is that while the exterior of the
ground beef is exposed to atmospheric oxygen
resulting in the full development of oxymyoglobin, the interior portion with the low partial
pressures of oxygen introduced through the
grinding process encourage the formation of
metmyoglobin. Therefore, the outside is red
and the inside is brown.

PREMATURE BROWNING/
PERSISTENT PINKNESS

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COOKED COLOR
Another concern that we hear about relates
to color changes after meat is cooked. We
expect that adequately cooked meats will have
the characteristic browned color. What we do
not expect is that once cooled, red color that
resembles a rarer degree of doneness sometimes occurs. The compounds responsible for
development of the brown color are somewhat
reversible, especially under refrigeration, and
create a red/pinkish color. So, when one slices
chilled roast beef, there can be a red/pinkish
color, even if it was thoroughly cooked before
chilling.

Reiser

Two other color problems occur in ground
beef. These problems are caused by differ-

ent conditions and result in different quality/
safety concerns. The first condition is referred
to as premature browning. When high-oxygen
(approximately 80 percent) modified atmosphere packaging began being used in caseready programs, it was discovered that ground
beef, when cooked, would begin to turn brown
at temperatures far lower than those degrees
of doneness most commonly related to safe
consumption. It was discovered that this high
concentration of oxygen caused some oxidation of the myoglobin to occur, and when the
cooking process started, ground beef would
turn brown well ahead of the normal process
most consumers associate with fully cooked
beef. This is one reason why USDA's cooking
guidelines urge consumers to use thermometers rather than cooked meat color to assure
that proper lethality temperatures are met.
The second condition is called persistent
pinkness. This problem is found in ground beef
patties that are adequately cooked to appropriate internal temperatures or combinations of
time and temperatures to ensure safety, but the
patties still have pinkish-to-red-colored centers
appearing that they have not been cooked
thoroughly or correctly. Persistent pinkness is
most often associated with patties that have
been manufactured from beef that has higherthan-normal pH, and with the seasonality
associated with the occurrence of dark cutting
beef, persistent pinkness usually follows
along. This condition is troublesome because
the patties have been cooked to appropriate
lethality temperatures, but they appear to be
undercooked, which causes consumers to
complain and often return hamburgers to the
counter at quick-service restaurants.

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Meat+Poultry - December 2019

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