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Food Preservation – Freezing
Introduction and Basic Information
Quick Freezing
(Resource: Cooking with Understanding, Nichols, H.L. Jr., North Castle Books, 1971.)
Quick freezing usually does less damage to the flavor and texture of properly prepared and packaged
food than any other method of preservation.
Fast freezing creates many fine crystals; slower freezing produces fewer but larger ones. Small
crystal formation gives a better texture, is less likely to rupture cell membranes of food, and it damages
the food less. Care should be taken to freeze food quickly.
Ice Formation – An Explanation
When water freezes, its molecules arrange themselves in crystals. As the crystals form, they
seed, or draw other molecules of water, separating them from other substances that are in combination
with the water. As the water molecules separate and freeze, the water is drawn from the cells of the food,
and as the water molecule leaves the cell, it punctures or tears the cell wall, damaging it by pulling the
water molecule through it. Quick freezing makes smaller crystals that do less damage. Quick freezing
also is more likely to freeze the molecules in place and give less time for them to separate and move
through cell walls.
Rules to Ensure Quick Freezing
1.
Place food in a freezer that maintains the temperature of 0 F during the freezing period.
2.
Do not put packages to be frozen in the door compartment of an upright freezer, as they are
usually several degrees warmer than the interior.
3.
Packages larger than a quart are not advisable. Small packages freeze faster than large ones.
4.
Wrapping in foil slows freezing somewhat.
5.
If placing several unfrozen packages in the freezer at the same time, put them in different areas
of the freezing compartment.
6.
Refer to the freezer instructions book for the pounds of fresh material it can freeze in one
batch. If information is not listed, assume you can freeze twice as many pounds as the freezer's
rated capacity in cubic feet.
7.
Follow quick freezing rules with meat. It will decrease the amount of runoff that occurs when
the meat thaws out.
Freezing Foods
1.
Always use quality foods.
2.
Don't overestimate your needs.
3.
A rapid turnover is important! Use a STORAGE CHART to keep a record of what you put in
your freezer, when you put it in, and the date by which the food should be removed.
4.
Preserve quality by:
a. Proper handling before freezing
b. Good packaging
c.
Storage at temperature no higher than 0 F
d. Proper handling and cooking after removing from freezer
Rules for Packaging Freezer Foods
Packages for freezing must give adequate protection against moisture and vapor losses or color, flavor,
and texture will deteriorate.
1.
Choose the size of container that will hold enough food for its use. 2. Select containers or
wrappings based on how you will handle the food when it is thawed for serving (e.g., meat loaves
in casserole dishes, bread to be reheated in aluminum foil, etc.)
2.
When filling containers, keep in mind that liquids expand when frozen. Always allow 1/2" head
space at the top of the cartons.
3.
Never use scotch tape or common gummed paper tapes to seal freezer packages. These
tapes loosen at low temperatures. Use freezer tape for sealing and labeling.
4.
To keep foods at the peak of freshness, they must be completely sealed to keep out air. When
the food surface is exposed to air, evaporations form of freezer bum-takes place.
How to Prevent Freezer Burn
1.
Use a cover that fits tightly. When in doubt, seal the edges with freezer tape.
2.
When using aluminum foil, shape it around the food.
3.
When ice cream has been left in a container, smooth off the surface and place a sheet of foil
directly over the ice cream.
4.
When using cellophane or plastic freezer bags, force out the air and use a twister around the
bag to keep out the air.
Wrapping Materials
Good wrapping materials are moisture-vaporproof or resistant. For most solid foods such as
meat, cake, pie, and bread, use freezer weight paper such as aluminum foil, cellophane, pliofilm, or other
transparent film. Polyethylene bags may be used for baked goods such as bread and cookies. To give
form to shapeless plastic bags, put them in paper cartons, then fill and freeze.
Liquid-packed foods may be packaged in heavily waxed cartons, glass freezer jars, and plastic
or aluminum containers. Choose a size that holds enough for one meal-quart containers hold 4-6
servings; pints, 2-3. Use only containers with wide top openings so the food does not have to be thawed
completely to remove it from the container. Some prepared foods like meat pies and casserole dishes
may be frozen in the containers in which they were prepared, ready for reheating at time of use.
Seal frozen food containers or packages with freezer locker tape, not general utility tape. Freezer locker
tape may also be used as a label on hard-to-mark wrapping materials.
Label jars, cartons, and packages with china marking pencil or soft crayon, available at stationery stores.
Be sure to DATE the package and IDENTIFY the contents.
How to Wrap for Freezing
Packaging With Freezer Sheet Material - the Drugstore Wrap.
1.
Place food in the center of the wrapping. Have enough length to overlap. Bring edges together
evenly above food.
2.
Fold edges over and over until fold is flat against the food. Press out air.
3.
Fold side edges; seal with freezer locker tape. Label plainly with contents and date.
Packaging in Rigid Container
Place food in container. Seal rigid food containers by adjusting the lids as required for the type
of package used. Casseroles made of ovenproof material can be covered and then sealed with freezer
tape. Label with contents and date.
Packaging in a Polyethylene Bag
Polyethylene bags are especially durable. Some are manufactured especially for freezing.
They can be sealed by twisting the tops and securing with soft twine or rubber binders. If using bags with
a zip-lock, be sure to expel as much air as possible before sealing. Label with contents and date.
Meats and Baked Goods
Meat can be frozen raw, cooked, or half-cooked because it has no problem of spoiling due to enzyme
action. Baked goods can be frozen as is for the same reason.
Fruits
Types of Preservatives Used to Stop Oxidation
1.
Sugar - Sugar helps slow enzyme damage and is desirable and often essential to counteract
acid flavors is some fruits.
a.
Dry method - 1/2 to 1 cup of sugar to a pound of fruit.
b.
Syrup - in general, thick or heavy syrups are used with high acid fruits. Medium and thin
syrups are used with lower acid fruits.
2.
ASCORBIC ACID - is added to sugar in the proportion of about 1/4 teaspoon to the cup and
mixed well before putting on the fruit. If it is added to the syrup, it is necessary to wait until the
syrup is cool and ready to use.
Vegetables
Vegetables must be partially cooked (blanched or scalded) before freezing to destroy enzymes and
prevent the deterioration they can cause.
Most enzymes are destroyed by keeping food at 212 F (boiling temperature) for a period varying from 50
seconds to 2 minutes depending on the vegetable. There are several ways to accomplish this:
a.
Water blanching
b.
Steam blanching
c.
Chilling
d.
Full cooking