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 compressorA condenserA 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:

· A large black grid mounted to the back of the freezer

Folded and placed under the freezer

· Coiled up and placed near the compressor

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.

EvaporatorThe 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 controlFreezers 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 hingesFreezer 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 16In 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.

EnzymesEnzyme 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.

PackagingProper 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 BurnFreezer 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 ChangesColor 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 RapidlyFreeze 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

Clarence Birdseye launches retail sales of frozen food products in Springfield, Massachusetts.

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.

The Birdseye Frosted Food Co. sells packaged meat, fish, oysters, vegetables and fruit from low temperature display cases in selected stores. 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

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 . 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. Boil-in bag packaging premiers. Swanson introduces the first TV dinner. The Association of Food & Drug Officials of the United States (AFDO) adopts a frozen food handling code. Fruits and vegetables are the primary frozen products for foodservice. Frozen foods enter the airline market.

The 60's

The microwave oven is introduced.

Frozen vegetable mixes become popular.

Frozen main courses and entrees take off in popularity. Frozen food sales soar when astronauts, upon return from landing on the moon, eat prepared frozen entrees and side dishes. McDonald's accepts frozen fish portions and meat patties.

The 70's

The first computerized supermarket check-out is put in place.

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

Cook-in-box vegetables and single-serve packages are introduced.

Frozen ethnic cuisines rise in popularity.

Frozen low calorie entrees are introduced. Frozen low priced entrees premiere. 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.

Almost 60 percent of married women are working as compared with 46 percent in 1973. The Home Meal Replacement trend dominates consumers' buying habits. Spicy, ethnic foods hit all-time high in popularity.

Kids cuisine makes a comeback.

Consumers eat up family size portions.

Club stores compete with traditional grocery outlets. Irradiation of meat is approved by FDA. · Hearty portions find new niche.· 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