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Is Frozen Food Safe?
Food stored constantly at 0 °F
will always be safe. Only the quality suffers with lengthy
freezer storage. Freezing keeps food safe by slowing the
movement of molecules, causing microbes to enter a dormant
stage. Freezing preserves food for extended periods because it
prevents the growth of microorganisms that cause both food
spoilage and foodborne illness.
Does Freezing Destroy Bacteria & Parasites?
Freezing to 0 °F inactivates
any microbes -- bacteria, yeasts and molds - - present in
food. Once thawed, however, these microbes can again become
active, multiplying under the right conditions to levels that
can lead to foodborne illness. Since they will then grow at
about the same rate as microorganisms on fresh food, you must
handle thawed items as you would any perishable food.
Trichina and other parasites can be destroyed by sub-zero
freezing temperatures. However, very strict
government-supervised conditions must be met. It is not
recommended to rely on home freezing to destroy trichina.
Thorough cooking will destroy all parasites.
Freshness & Quality
Freshness and quality at the
time of freezing affect the condition of frozen foods. If
frozen at peak quality, foods emerge tasting better than foods
frozen near the end of their useful life. So freeze items you
won't use quickly sooner rather than later. Store all foods at
0° F or lower to retain vitamin content, color, flavor and
texture.
Nutrient Retention
The freezing process itself
does not destroy nutrients. In meat and poultry products,
there is little change in nutrient value during freezer
storage.
Enzymes
Enzyme activity can lead to
the deterioration of food quality. Enzymes present in animals,
vegetables and fruit promote chemical reactions, such as
ripening. Freezing only slows the enzyme activity that takes
place in foods. It does not halt these reactions which
continue after harvesting. Enzyme activity does not harm
frozen meats or fish and is neutralized by the acids in frozen
fruits. But most vegetables that freeze well are low acid and
require a brief, partial cooking to prevent deterioration.
This is called "blanching." For successful freezing, blanch or
partially cook vegetables in boiling water or in a microwave
oven. Then rapidly chill the vegetables prior to freezing and
storage. Consult a cookbook for timing.
Packaging
Proper packaging helps
maintain quality and prevent "freezer burn." It is safe to
freeze meat or poultry directly in its supermarket wrapping
but this type of wrap is permeable to air. Unless you will be
using the food in a month or two, overwrap these packages as
you would any food for long-term storage using airtight
heavy-duty foil, (freezer) plastic wrap or freezer paper, or
place the package inside a (freezer) plastic bag. Use these
materials or airtight freezer containers to repackage family
packs into smaller amounts. It is not necessary to rinse meat
and poultry before freezing. Freeze unopened vacuum packages
as is. If you notice that a package has accidentally been torn
or has opened while food is in the freezer, the food is still
safe to use; merely overwrap or rewrap it.
Freezer Burn
Freezer burn does not make
food unsafe, merely dry in spots. It appears as grayish-brown
leathery spots and is caused by air reaching the surface of
the food. Cut freezer-burned portions away either before or
after cooking the food. Heavily freezer-burned foods may have
to be discarded for quality reasons.
Color Changes
Color changes can occur in
frozen foods. The bright red color of meat as purchased
usually turns dark or pale brown depending on its variety.
This may be due to lack of oxygen, freezer burn or abnormally
long storage.
Freezing doesn't usually cause color changes in poultry.
However, the bones and the meat near them can become dark.
Bone darkening results when pigment seeps through the porous
bones of young poultry into the surrounding tissues when the
poultry meat is frozen and thawed.
The dulling of color in frozen vegetables and cooked foods is
usually the result of excessive drying due to improper
packaging or over-lengthy storage.
Freeze Rapidly
Freeze food as fast as
possible to maintain its quality. Rapid freezing prevents
undesirable large ice crystals from forming throughout the
product because the molecules don't have time to take their
positions in the characteristic six-sided snowflake. Slow
freezing creates large, disruptive ice crystals. During
thawing, they damage the cells and dissolve emulsions. This
causes meat to "drip"--lose juiciness. Emulsions such as
mayonnaise or cream will separate and appear curdled.
Ideally, a food 2-inches thick should freeze completely in
about 2 hours. If your home freezer has a "quick-freeze"
shelf, use it. Never stack packages to be frozen. Instead,
spread them out in one layer on various shelves, stacking them
only after frozen solid.
Refrigerator - Freezers
If a refrigerator freezing
compartment can't maintain zero degrees or if the door is
opened frequently, use it for short-term food storage. Eat
those foods as soon as possible for best quality. Use a
free-standing freezer set at 0° F or below for long-term
storage of frozen foods. Keep a thermometer in your freezing
compartment or freezer to check the temperature. This is
important if you experience power-out or mechanical problems.
Length of Time
Because freezing keeps food
safe almost indefinitely, recommended storage times are for
quality only. Refer to the freezer storage chart at the end of
this document, which lists optimum freezing times for best
quality.
If a food is not listed on the chart, you may determine its
quality after defrosting. First check the odor. Some foods
will develop a rancid or off odor when frozen too long and
should be discarded. Some may not look picture perfect or be
of high enough quality to serve alone but may be edible; use
them to make soups or stews. Cook raw food and if you like the
taste and texture, use it.
Safe Defrosting
Never defrost foods in a
garage, basement, car, dishwasher or plastic garbage bag; out
on the kitchen counter, outdoors or on the porch. These
methods can leave your foods unsafe to eat.
There are three safe ways to defrost food: in the
refrigerator, in cold water, or in the microwave. It's best to
plan ahead for slow, safe thawing in the refrigerator. Small
items may defrost overnight; most foods require a day or two.
And large items like turkeys may take longer, approximately
one day for each 5 pounds of weight.
For faster defrosting, place food in a leak proof plastic bag
and immerse it in cold water. (If the bag leaks, bacteria from
the air or surrounding environment could be introduced into
the food. Tissues can also absorb water like a sponge,
resulting in a watery product.) Check the water frequently to
be sure it stays cold. Change the water every 30 minutes.
After thawing, cook immediately.
When microwave-defrosting food, plan to cook it immediately
after thawing because some areas of the food may become warm
and begin to cook during microwaving.
Refreezing
Once food is thawed in the
refrigerator, it is safe to refreeze it without cooking,
although there may be a loss of quality due to the moisture
lost through defrosting. After cooking raw foods which were
previously frozen, it is safe to freeze the cooked foods. If
previously cooked foods are thawed in the refrigerator, you
may refreeze the unused portion.
If you purchase previously frozen meat, poultry or fish at a
retail store, you can refreeze if it has been handled
properly.
Cooking Frozen Foods
Raw or cooked meat, poultry
or casseroles can be cooked or reheated from the frozen state.
However, it will take approximately one and a half times the
usual cooking time for food which has been thawed. Remember to
discard any wrapping or absorbent paper from meat or poultry.
When cooking whole poultry, remove the giblet pack from the
cavity as soon as you can loosen it. Cook the giblets
separately. Read the label on USDA-inspected frozen meat and
poultry products. Some, such as pre-stuffed whole birds, MUST
be cooked from the frozen state to ensure a safely cooked
product.
LOOK FOR THE
USDA OR STATE MARK OF INSPECTION
Poultry Seal
The inspection mark on the
packaging tells you the product was prepared in a USDA or
State-inspected plant under controlled conditions. Follow the
package directions for thawing, reheating, and storing.
Power Outage in Freezer
If there is a power outage,
the freezer fails, or if the freezer door has been left ajar
by mistake, the food may still be safe to use. As long as a
freezer with its door ajar is continuing to cool, the foods
should stay safe overnight. If a repairman is on the way or it
appears the power will be on soon, just don't open the freezer
door.
A freezer full of food will usually keep about 2 days if the
door is kept shut; a half-full freezer will last about a day.
The freezing compartment in a refrigerator may not keep foods
frozen as long. If the freezer is not full, quickly group
packages together so they will retain the cold more
effectively. Separate meat and poultry items from other foods
so if they begin to thaw, their juices won't drip onto other
foods.
When the power is off, you may want to put dry ice, block ice,
or bags of ice in the freezer or transfer foods to a friend's
freezer until power is restored. Use an appliance thermometer
to monitor the temperature.
When it is freezing outside and there is snow on the ground,
it seems like a good place to keep food until the power comes
on; however, frozen food can thaw if it is exposed to the
sun's rays even when the temperature is very cold.
Refrigerated food may become too warm and foodborne bacteria
could grow. The outside temperature could vary hour by hour
and the temperature outside will not protect refrigerated and
frozen food. Additionally, perishable items could be exposed
to unsanitary conditions or to animals. Animals may harbor
bacteria or disease; never consume food that has come in
contact with an animal.
To determine the safety of foods when the power goes on, check
their condition and temperature. If food is partly frozen,
still has ice crystals, or is as cold as if it were in a
refrigerator (40 °F), it is safe to refreeze or use. It's not
necessary to cook raw foods before refreezing. Discard foods
that have been warmer than 40 °F for more than 2 hours.
Discard any foods that have been contaminated by raw meat
juices. Dispose of soft or melted ice cream for quality's
sake.
Frozen Cans
Accidentally frozen cans,
such as those left in a car or basement in sub-zero
temperatures, can present health problems. If the cans are
merely swollen -- and you are sure the swelling was caused by
freezing -- the cans may still be usable. Let the can thaw in
the refrigerator before opening. If the product doesn't look
and/or smell normal, throw it out. DO NOT TASTE IT! If the
seams have rusted or burst, throw the cans out immediately,
wrapping the burst can in plastic and disposing the food where
no one, including animals can get it.
Frozen Eggs
Shell eggs should not be
frozen. If an egg accidentally freezes and the shell cracked
during freezing, discard the egg. Keep an uncracked egg frozen
until needed; then thaw in the refrigerator. It can be hard
cooked successfully but other uses may be limited. That's
because freezing causes the yolk to become thick and syrupy so
it will not flow like an unfrozen yolk or blend very well with
the egg white or other ingredients.
Freezer Storage Chart (0 °F)
Note: Freezer storage is for quality only. Frozen foods remain
safe indefinitely.
Item Months
Casseroles 2 to 3
Egg whites or egg substitutes 12
Frozen Dinners and Entrees 3 to 4
Gravy, meat or poultry 2 to 3
Ham, Hotdogs and Lunchmeats 1 to 2
Meat, uncooked roasts 4 to 12
Meat, uncooked steaks or chops 4 to 12
Meat, uncooked ground 3 to 4
Meat, cooked 2 to 3
Poultry, uncooked whole 12
Poultry, uncooked parts 9
Poultry, uncooked giblets 3 to 4
Poultry, cooked 4
Soups and Stews 2 to 3
Wild game, uncooked 8 to 12
October 2005 |
