freezing fruits and vegetables at home. 2 adapted from: cooperative extension service college of...

Freezing Fruits and Vegetables at Home

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Adapted from: Cooperative Extension Service College of Family and Consumer Sciences University of Georgia

MARTHA SMITH PATNOAD, MS, CP-FSCE FOOD SAFETY EDUCATION SPECIALIST401-874-2960mpatnoad@uri.edu

NICOLE RICHARD, MSRESEARCH ASSISTANT401-874-2977nicolerichard@uri.edu

DEPT OF NUTRITION AND FOOD SCIENCESUNIVERSITY OF RHODE ISLAND

8/2010

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Advantages of Freezing Many foods can be frozen. Good natural color, flavor and

nutritive value retained. Texture usually better. Takes less time Easy to do Foods can be frozen in any

quantity

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How Freezing Affects Food Textural Changes

The water in food freezes and expands.

Ice crystals cause the cell walls of fruits and vegetables to rupture, making them softer when thawed.

Some vegetables with very high water content do not freeze well: celery, lettuce, some tomatoes.

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How Freezing Affects Food

To prevent color and flavor changes, as well as loss of some nutrients, enzymes should be controlled

Enzymes are small proteins in foods that start or help with reactions, such as those that cause browning, off-flavors, ripening, mushiness, etc

. Are slowed down but not destroyed during

freezing.

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How Freezing Affects Food

Enzymes in Vegetables Are destroyed by blanching which is

a quick heat and quick cooling

Enzymes in Fruits Usually controlled the addition of

sugar and antioxidants such as ascorbic acid ( vitamin C) or ascorbic acid mixtures

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How Freezing Affects Food

Fluctuating Freezer Temperatures Ice in food thaws a little and then

re-freezes Ice crystals get bigger each time. Food becomes mushy as large ice

crystal growth damages cells Moisture is pulled out of the food Other quality losses speeded up due to

higher temperatures. Moisture Loss

Freezer burn – tough and dry, but safe.

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General Freezing Guidelines

1. Freeze foods at 0oF or lower. 24 hours in advance of freezing large

quantities of food, set freezer at -10oF or lower

2. Keep work areas, containers, utensils clean

3. Follow established directions.4. Freeze foods immediately after prep.5. Do not overload freezer

Freeze amount that will freeze in 24 hours (2 to 3 pounds of food per cubic foot).

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6. Pack already frozen foods together to prevent thawing

7. Place unfrozen foods in contact with surfaces and in coldest parts of freezer

8. Leave space around packages so cold air can circulate.

9. Arrange frozen foods so that the foods frozen longer can be used first

10. Check thermometer

11. Time of storage- 1 year at 0 F

Freezing Guidelines, cont.

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Packaging

Moisture-vapor resistant Prevents transfer of moisture and air in and out of

the package

Durable and leak-proof Does not become brittle and crack at low

temperatures Resistant to oil, grease or water Protects foods from absorption of “off”

flavors or odors. Easy to seal and label.

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Packaging

Rigid Containers Plastic freezer containers. Wide-mouth canning/freezing jars.

Good for liquids or soft, juicy, or liquid-packed foods.

May be reusable. Hold their shape and can be

stored upright.

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Packaging

Bags Wraps

» plastic (such as polyethylene) » heavy-duty aluminum foil » laminated paper- “freezer paper”

Good for firm, non-juicy foods.

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Packaging Vacuum Sealers

- Always defrost in the refrigerator

- Cut several holes in the

plastic so

environment in

the bag is not

“air-free”

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Packing Foods

Food must be cool

Pack in serving size quantities.

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Packing Foods to be Frozen

Pack foods tightly – Avoid trapped air (oxygen)

Allow for headspace as food may expand except: uneven vegetables like broccoli and asparagus

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Packing Foods- Sealing

Use tight lid on rigid containers Keep sealing edges clean and dry. Use freezer tape over

seams of looser-fitting covers.

Trapped food or liquids in sealing area will freeze, expand, and loosen seal.

Always label with date and contents

Press all air from bagged foods. Except for headspace.

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Freezing Fruits

Frozen in many forms – Whole, sliced, crushed, juiced.

Best quality – Optimum maturity and freshness. Immature or overripe both produce lower

quality when frozen. Wash and work with small amounts at a time

to preserve best quality.

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Preventing Fruit Darkening

Ascorbic acid ( Vitamin C)

Heating the fruit

Ascorbic Acid Mixtures-“Fruit Fresh” and others- Have some other added ingredients.-Follow package directions to obtain

correct strength

Do not work as well: Citric acid Lemon juice Sugar syrup Salt/vinegar solution

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Sweetened Packs for Fruit

Sugar Syrup Pack Better texture. Not needed for safety. Fruits should be covered with

syrup. Place crumpled water-resistant paper

in top of container.

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Preparing Peaches in Syrup

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Sweetened Packs for Fruit

Sugar Pack Sliced soft fruits (strawberries, peaches,

etc.) make their own syrup when mixed with the right proportion of sugar.

Layer fruit and sugar in bowl or pan. Allow mixture to stand 15 minutes to

make juice or “syrup” before packaging.

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Unsweetened Packs for Fruit

Dry Pack Good for small whole fruits

such as berries that don’t need sugar.

Simply pack into containers and freeze.

Or may be frozen individually, in single layer, on a tray first. “Tray pack” – next slide

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Dry Tray Pack for Fruit

Fruit pieces may be frozen individually, in single layer, on a tray first.

Freeze until firm then package in rigid container or bag.

Will pour out of container easily when frozen.

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Dry “Tray” Pack for Fruit Can remove only the amount needed at one

time. Fruit pieces retain shapes. Fruit pieces do not “clump” as when packed

directly into containers or with sugar syrup.

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Unsweetened Packs for Fruit Pectin Syrup

Good for strawberries and peaches. Mix 1 package powdered pectin and 1 cup

water. Bring to boil, boil 1 minute. Remove from heat, cool and add 1-3/4 cups more water.

Water or Unsweetened Juice Packs Texture will be mushier. Color poorer. Freezes harder, takes longer to thaw.

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Sugar Substitutes

May be used in the pectin syrup, juice or water packs.

Or could be added just before serving. These do not help with color retention

or texture, like sugar does. Use amounts on product labels or to

taste.

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Freezing Vegetables

Select young, tender, high-quality vegetables.

Sort for size and ripeness. Wash and drain before removing skins or

shells. Wash small lots at a time, lifting out of

water. DO NOT SOAK. Work in small quantities, preparing as

directed.

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Preventing Flavor and Color Changes in Vegetables

Blanching

Primary method to destroy enzymes for vegetables.

Will also soften hard veggies to make packaging easier.

Will also remove some microorganisms. Under-blanching can be harmful; it will

stimulate enzymes and not destroy them. Check required blanching times for each food.

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How to Blanch Vegetables

Use specific directions.

Work in small quantities.

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How to Blanch Vegetables

In Boiling Water Use blancher with lid or a

kettle with basket and lid. Have 1 gallon water per 1 lb. of vegetables. Place vegetables in blanching basket. Lower vegetable into vigorously boiling

water. Put lid on. Water should hardly stop boiling or return to a boil within a minute.

If water keeps boiling, begin timing immediately. Otherwise, wait for water to come back to a boil.

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How to Blanch Vegetables

Steam Blanching Use kettle with tight lid and basket. 1” to 2” of boiling water in bottom

of pan. Vegetable should be in a single

layer in basket. Start timing when covered.

Takes 1-1/2 times longer than water blanching. Check times, however, for each food.

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How to Blanch Vegetables

Microwave Blanching Not widely recommended at this time. May not be effective – enzymes not

inactivated completely by uneven heating. Usually does not save time.

Have to do very small quantities. If you have directions from a source you

trust, try small quantities at first and see if you like the quality after a period of frozen storage.

This is not a safety issue, as long as frozen food is always stored frozen, but improper blanching will affect quality.

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How to Blanch Vegetables

After blanching in water or steam, cool immediately in cold water.

Change water frequently or use running water or iced water (1 lb. ice per 1 lb. vegetable).

Cooling time should be the same as the blanching time.

Drain thoroughly.

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Types of Pack for Vegetables

Dry Pack Pack after the vegetables are

blanched, cooled, and drained. Pack quickly, pushing air out of

package as you work towards top.

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Types of Pack for Vegetables

Tray Pack After draining, spread pieces in a

single layer on a shallow pan. Freeze firm. After first hour, check often. Package quickly, pushing air out as

you work.

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Disclaimer and Credits Disclaimer:

Trade and brand names are used only for information. The Cooperative Extension Service, University of Georgia College of Agricultural & Environmental Sciences and College of Family & Consumer Sciences, and the U.S. Department of Agriculture do not guarantee nor warrant published standards on any product mentioned; neither does the use of a trade or brand name imply approval of any product to the exclusion of others which may also be suitable.

Document Use: Permission is granted to reproduce these materials in whole or in part for

educational purposes only (not for profit beyond the cost of reproduction) provided the author and the University of Georgia receive acknowledgment and this notice is included:

Reprinted (or Adapted) with permission of the University of Georgia. Andress, E.L. 2003. Freezing fruits and vegetables at home (slides). Athens, GA: The University of Georgia, Cooperative Extension Service.

This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.