Transcript Different Ways to Preserve Foods

Different Ways to Preserve Foods:
1. Refrigeration and freezing: these are the
most popular ways. Refrigeration slows
bacteria to a crawl to prevent spoiling.
Freezing stops bacteria action completely. It
can be used on all foods with little effect to
the taste, except for fruit.
2. Dehydration: most bacteria will die when
dehydrated. Drying will change the taste and
texture of the food. Often it will change it
altogether. An example of this would be a
raisin.
3.
Pickling: Is used for meat, fruit, eggs, and vegetables
using salt, acid and vinegar to stop bacterial growth.
Food is soaked in 10% salt water brine, rinsed and stored
in vinegar. This can last for years.
4.
Irradiation: This kills bacteria without changing the food.
Food is sealed in plastic, then irradiated . It will become
sterile and can be stored on a shelf. It doesn’t change
the taste and can prevent spoilage, but is debated
because of the radiation used.
Refrigeration and Freezing
Temperature is measured in degrees on various scales . . .
At what temperature
does water freeze? (And, at the opposite state of matter, at what temperature does
water boil?) Turn to page 15 in your student packet to design an experiment that will
answer those questions on the Farenheit and Celsius scales.
HOW FREEZERS WORK
You'll more quickly understand freezer cooling systems if you think of
their action as "removing heat from the air in the freezer" rather than
"cooling the air in the freezer." All residential freezers work on the same
principle for cooling. They all have:
A compressor
A condenser
A metering device (capillary tube)
An evaporator
Compressor
The compressor is the motor of the cooling system.
It's normally at the bottom of the freezer in the back.
It's almost always black and about the size of a
football. If the freezer is self-defrosting, the
compressor may be behind a thin panel.
The compressor runs whenever the freezer
thermostat calls for cooling (and the defrost timer is
not in a defrost cycle, for self-defrosting units). It is
normally very quiet. When running, it is
compressing a refrigerant that is in a low-pressure
gaseous state to a high-pressure gas.
Condenser
The condenser is a series of tubes with fins attached to
them, similar to a radiator. It's always somewhere on the
outside of the freezer. On many freezers, it is integrated
within the freezer cabinet and is completely out of sight. If
the freezer is self-defrosting it may be:
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A large black grid mounted to the back of the freezer
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Folded and placed under the freezer
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Coiled up and placed near the compressor
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Integrated in the liner of the freezer
If the condenser isn't a big grid on the back of the
freezer, it will always have a cooling fan nearby to
draw room air over the tubes and fins--to dissipate
the heat from the tubes and fins. The high-pressure
refrigerant gas, coming from the compressor, flows
through the condenser and becomes a liquid. As this
occurs, the refrigerant gives off heat. The heat is
conducted away from the tubes by the fins.
Metering device (capillary tube)
The metering device in most household freezers is
a capillary tube, a tiny copper tube. The capillary
tube is attached from the end of the condenser to
the beginning of the evaporator. The capillary tube
controls the pressure and flow of the refrigerant as
it enters the evaporator.
Once the liquid refrigerant has traveled the length
of the condenser, it is forced through the capillary
tube.
Evaporator
The evaporator is always located on the inside of the
freezer. It may be:

Integrated within the walls of the freezer, as in a
chest freezer.

Integrated with the shelves of the freezer, as in an
upright freezer.

Concealed behind a panel on the inside of the
freezer.
When the liquid refrigerant comes out of the small
capillary tube, it's injected into the larger tubes of the
evaporator causing a pressure drop. This pressure drop
allows the refrigerant to expand back into a gaseous
state. This "change of state" -from liquid to gas-absorbs
heat. The gaseous refrigerant travels through the
evaporator tubes, back out of the freezer and down to
the compressor to begin the circulation process again.
Because the evaporator is absorbing heat, it is very cold
to the touch. The coldness causes any humidity in the
air to freeze on the evaporator as ice or frost. The fan
inside the freezer compartment circulates the air to
keep the temperature constant.
Temperature control
Freezers have a thermostat to maintain the
proper temperature. These are usually very
simple devices. When the freezer reaches the set
temperature, the thermostat interrupts the
electricity flow to the compressor, which stops
cooling.
Door seals and hinges
Freezer doors have a seal--a rubber-like gasket attached to
the door. The seal's job is to keep the cool air inside the
freezer and the outside room air out.
The seal is lined with a magnet that runs its length and
width. The magnet helps to hold the door closed and
creates a tight seal. The screws that hold the seal to the
door also hold the door liner in and help to "square" the
door.
The hinges allow the door to swing open. Some hinges also
assist the door in closing. For the door to close properly,
the hinges must be correctly adjusted.
How A Freezer Works Summary
Complete Page 16
In your Student Packet
Foods in the freezer -- are they safe?
Every year, thousands of callers to the USDA Meat and Poultry
Hotline aren't sure about the safety of items stored in their
own home freezers. The confusion seems to be based on the
fact that few people understand how freezing protects food.
Here is some information on how to freeze food safely and how
long to keep it.
What Can You Freeze?
You can freeze almost any food. Some exceptions are
canned food or eggs in shells. However, once the food (such
as a ham) is out of the can, you may freeze it.
Being able to freeze food and being pleased with the quality
after defrosting are two different things. Some foods simply
don't freeze well. Examples are mayonnaise, cream sauce
and lettuce. Raw meat and poultry maintain their quality
longer than their cooked counterparts because moisture is
lost during cooking.
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?
Freezing to 0 °F inactivates microbes -- bacteria - - 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.
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, because it is
dried out, not because it is contaminated or spoiled.
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.
Frozen Food Notes
Use the headings on page 17
In your Student Packet
To gather notes on frozen food.
Clarence Birdseye and the
History of Frozen Food Technology
The history of frozen foods and the Birds Eye® brand is far from
frozen in time: In fact, it continues to this day and into the future.
Though the practice of freezing food has been traced to 1626, Birds
Eye began to take shape in the early 1920s when Clarence
Birdseye noticed that the fish he caught while on a trip near the
Arctic quickly froze. Later, when thawed, the fish tasted as fresh as
if he had just caught them. From that observation history was made.
Clarence had discovered the basis for an entirely new type of
freezing operation that today allows growing populations to enjoy
the freshest, healthiest vegetables available.
The 30's
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Clarence Birdseye launches retail sales of frozen food products in
Springfield, Massachusetts.
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The Postum Company, which later became General Foods Company,
buys Birdsye's patents covering several aspects of food freezing
processes, including package design and a double-plate freezer.
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The Birdseye Frosted Food Co. sells packaged meat, fish, oysters,
vegetables and fruit from low temperature display cases in selected stores.
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Mechanical refrigeration assumes an almost indispensable part of the
food distribution system in the United States.
On March 6, 1930, in Springfield,
Massachusetts, General Foods, via
Birds Eye, conducts what is now called
"the Springfield Experiment" in 18 retail
stores to see how consumers will react
to frozen foods; today, the experiment is
considered the birth of retail frozen
foods. The initial Birds Eye line features
26 items, including 18 cuts of frozen
meat, spinach and peas, a variety of
fruits and berries, blue point oysters and
fish fillets. By May, sales increase
dramatically.
The 40's
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Annual frozen food production rises from slightly over 1.5 billion pounds
to 2.5 billion pounds .

New frozen products are introduced, including puff pastries, hors
d'oeuvres, soups, entrees, french fries, Mexican cuisine, whipped topping,
meat pies, seafood and pizza .
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Foil packaging is used for frozen products.

The Food and Drug Administration gives increasing attention to industry
packing practices and sanitation methods, and begins to establish standards
for frozen food products.
The 50's

Frozen food sales exceed the $1 billion mark.

The introduction of precooked or prepared frozen foods opens up an
entirely new field for industry growth.
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Boil-in bag packaging premiers.
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Swanson introduces the first TV dinner.
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The Association of Food & Drug Officials of the United States (AFDO)
adopts a frozen food handling code.
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Fruits and vegetables are the primary frozen products for foodservice.
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Frozen foods enter the airline market.
The 60's
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The microwave oven is introduced.
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Frozen vegetable mixes become popular.
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Frozen main courses and entrees take off in popularity.
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Frozen food sales soar when astronauts, upon return from landing on the
moon, eat prepared frozen entrees and side dishes.
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McDonald's accepts frozen fish portions and meat patties.
The 70's
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The first computerized supermarket check-out is put in place.
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Bar codes begin appearing on food packaging.
Frozen stir fry vegetables are introduced.
Paper tray packaging is used for oven and microwave cooking.
Burger King decides to use frozen meat patties and other products.
Supermarkets include heated frozen food products at deli counters.
The 80's
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Cook-in-box vegetables and single-serve packages are introduced.
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Frozen ethnic cuisines rise in popularity.
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Frozen low calorie entrees are introduced.
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Frozen low priced entrees premiere.
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Fast-food items are frozen for retail, including hamburgers, french
fries, milkshakes and breakfasts

Lack of freezer space in retail outlets increasingly becomes a problem
for the industry.

Microwave items increase in popularity.
•
Newly designed cryogenic railcar for transporting frozen foods are
introduced.
The 90's

FDA deems frozen fruit and vegetable products to have equivalent or superior
nutrient profiles as their fresh counterparts.
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Almost 60 percent of married women are working as compared with 46 percent
in 1973.
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The Home Meal Replacement trend dominates consumers' buying habits.
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Spicy, ethnic foods hit all-time high in popularity.
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Kids cuisine makes a comeback.
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Consumers eat up family size portions.
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Club stores compete with traditional grocery outlets.
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Irradiation of meat is approved by FDA.
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Hearty portions find new niche.
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Frozen meal starters and one-dish prepared meals make their debut, and have
immediate success.
The 00's
The frozen food industry is limited
only by its imagination…
What do you think is next for the
frozen food industry?
Be as creative or imaginative as
you can.
List your ideas on page 18
of your student packet