Freezing Vegetables - College of Agricultural, Consumer and

Freezing Vegetables
Guide E-320
Revised by Nancy C. Flores and Cindy Schlenker Davies1
Cooperative Extension Service • College of Agricultural, Consumer and Environmental Sciences
INTRODUCTION
Fresh vegetables can be frozen quickly and easily during
the harvest season. Whether you freeze purchased or
home-grown vegetables, the keys to a successful product
are using vegetables at the peak of ripeness and freezing
quickly after purchase or harvest.
SELECTION AND PURCHASE
Choose vegetables that are young and tender. Wash well
and rinse twice in fresh water to remove dirt. Trim away
any damaged spots, tough stems, and leaves. Cut into
desired sizes.
Cabbage, cucumbers (unless marinated as a slaw),
celery, cress, endive, lettuce, parsley, radishes, and whole
potatoes (baked or boiled) do not freeze well.
FREEZER FOOD SAFETY
Meat, poultry, fish, and eggs must be kept refrigerated at
or below 40°F, and frozen food must be kept at or below
0°F. If there is a power failure, maintain cold temperatures of the refrigerator and freezer by keeping doors
closed as much as possible. A refrigerator will keep food
safely cold for about 4 hours if it is unopened. A full
freezer will hold its temperature longer than a half-full
freezer for approximately 48 hours if the door remains
closed. During a prolonged power outage, use dry ice or
block ice. Fifty pounds of dry ice should maintain frozen temperatures for an 18-cubic foot full freezer
for 2 days.
Frozen vegetable juices and home and commercially
prepared frozen vegetables that have partially thawed
can be re-frozen if they contain ice crystals and feel
as cold as refrigerated product. Frozen vegetables that
have thawed and been held above 40°F for over 2 hours
(but less than 6 hours) can be re-frozen, but should be
checked for mold, yeasty smell, or sliminess. Discard
any questionable product, and do not re-freeze product
that was allowed to thaw for more than 6 hours.
© Petar Vician | Dreamstime.com
BLANCHING
Although freezing slows the action of ripening enzymes,
it doesn’t completely halt it. Blanching is a quick heat
treatment to inactivate the ripening enzymes in vegetables. This will help to preserves their color, texture, and
flavor for up to 12 months in the freezer.
Except for onions and green peppers, vegetables should
be either water or steam blanched before being frozen.
Some vegetables, such as mushrooms, eggplant, and summer squash, taste better if sautéed briefly in oil, unsalted
butter, or margarine. Chill before packaging, then freeze.
Equipment List
Cutting board and knife
Peeler/corer
Tongs or slotted spoon
Freezer containers or plastic bags
Pot holders x 2
Paper towel roll
Cloth towels x 2
Cooking pot with basket (such as vegetable steamer)
Large strainer in an ice water bath
Accurate timer
Dish soap and scrubber
Respectively, Extension Food Technology Specialist, Department of Extension Family and Consumer Sciences; and County Program Director and Extension
Home Economist, Bernalillo County Extension Office, New Mexico State University.
1
To find more resources for your business, home, or family, visit the College of Agricultural, Consumer and Environmental
Sciences on the World Wide Web at aces.nmsu.edu
Steps for Water Blanching
Place the washed, prepared vegetables in a pot of boiling water.
Use 1 gallon of water for each
pound (about 2 cups) of prepared
vegetables. See Table 1 for recommended blanching times for different vegetables. Start timing the
blanching action when the water
returns to boiling after adding the
vegetables. When the blanching
time is over, remove vegetables and
plunge them immediately into cold
(preferably ice) water for the same
amount of time that you blanched
the vegetables. This cold bath stops
the cooking action.
Steps for Steam Blanching
© Julia Pfeifer | Dreamstime.com
Place 2 cups or about 1 pound of
prepared vegetables in a single layer in a steaming basket
and lower into a pot containing 1 gallon of boiling water.
The vegetables should be above the water. Cover with a
tight-fitting lid and start counting the blanching time
when steam comes up around the pot lid; see Table 1 for
blanching times. Plunge vegetables into an ice water bath.
Microwave Blanching
You can use a microwave oven to blanch small quantities
of vegetables. However, there is evidence that his method does not fully inactivate enzymes and could result in
poor quality over a prolonged storage time. Additionally, there is no time or money saved when microwave
blanching vegetables.
PACKING FOOD INTO
FREEZING CONTAINERS
Blanched vegetables should be drained and fully frozen
before packing into moisture-proof freezer containers
for long-term storage. Blot dry drained vegetable pieces
with a clean paper towel to remove surface moisture.
Spread out vegetable pieces onto a baking sheet lined
with wax or parchment paper and place the baking sheet
in the freezer. Once pieces are completely frozen, transfer to labeled bags or containers.
Both freezer bags and square containers can be
packed economically to conserve space in the freezer.
Fill rigid containers to the expansion line. If you use
zippered freezer bags, lay bags on the counter after filling and press out air. Close zipper bags, leaving about
1 inch open, and use a drinking straw to suck air out
before closing completely. If using a bag with a twist tie
closure, gather the bag edges around a drinking straw
and draw out air before twisting and tying.
A vacuum sealer can be used to package frozen vegetables. Closely follow the manufacturer’s operation
manual for directions. To prevent botulism poisoning,
vacuum-sealed foods must be kept frozen until ready to
use and should be cooked thoroughly before consuming.
Use a moisture-proof freezer pen to label containers
with packing date and contents. When freezing, place
containers in the coldest area of the freezer with about
1 inch around the containers for cold air circulation
until the vegetables are frozen. After containers are fully
frozen, stack them tightly.
Freeze only the amount of food that the freezer
can handle efficiently. A good rule of thumb is 2 to 3
pounds of food for each cubic foot of storage space.
Overloading slows the freezing process and adversely affects the vegetables’ quality, especially corn on the cob.
Make a food inventory and post it on the freezer. List
the date of freezing, the foods, and number and sizes of
containers. Keep a pen close to mark the list as containers are used.
THAWING AND PREPARING
VEGETABLES TO EAT
Except for corn on the cob, vegetables can be cooked
with little or no thawing. Corn on the cob should be
thawed completely before cooking. Greens should be
partially thawed and separated before cooking. Because
the vegetables were blanched before freezing, they will
cook quickly.
When cooking, use the smallest amount of water possible to conserve nutrients. Cook only the amount you
need for the meal. Avoid letting vegetables stand after
cooking because nutrients leach into the cooking water.
Guide E-320 • Page 2
Table 1. Freezing Techniques for Vegetables
Vegetable
Preparation
Blanching Times and Freezing Techniques
Artichoke hearts
Remove all leaves, woody stems, and fuzzy portion.
Wash hearts in cold water and drain.
Water blanch 7 min; drain, pack, and seal.
Asparagus
Wash. Sort by size. Snap off tough ends. Cut stalks
into 2-inch lengths or leave whole.
Water blanch
Small: 1 1/2 min
Medium: 2 min
Large: 3 min
Steam blanch
Small: 2 1/2 min
Medium: 3 min
Large: 4 min
Beans (snap, green, or wax)
Wash. Trim ends. Cut if desired.
Water blanch
Whole: 3 min
Cut: 2 min
Steam blanch
Whole: 4 min
Cut: 3 min
Beets
Wash. Remove leafy tops, leaving 1 inch of stem.
Cook until tender, 25–30 minutes for small beets,
45–50 minutes for medium beets. Cool promptly,
peel, trim tap root and stem. Cut into slices or
cubes.
Broccoli
Wash. Trim leaves. Cut into pieces.
Water blanch 3 min
Steam blanch 3 min
Brussels sprouts
Wash. Remove outer leaves.
Water blanch 4 min
Steam blanch 5 min
Cabbage
Wash. Discard coarse outer leaves.
Water blanch
Wedges: 3 min
Shredded: 1 1/2 min
Steam blanch
Wedges: 4 min
Shredded: 2 min
Carrots
Wash, peel, and trim. Cut if desired; leave small
carrots whole.
Water blanch
Whole: 5 min
Sliced: 2 min
Cauliflower
Discard leaves and stem. Wash head, then break
into florets.
Add 1 tablespoon vinegar to water.
Corn, kernels
Remove husks and silks and trim ends. Wash ears.
Water blanch medium-sized ears, 3–4 ears at a
time, for 4 min. After blanching, cut kernels (about
2/3 depth) from cob, bag kernels, and freeze.
Corn on the cob
Remove husks and silks and trim ends. Wash ears.
Water blanch medium-sized ears for 7 min. Cool
and drain. Wrap ears individually in plastic wrap.
Pack wrapped ears in plastic freezer bags.
Eggplant
Wash, peel, and slice 1/3 inch thick.
Water blanch for 4 min in 1 gallon of boiling water
containing 1 1/2 tablespoons citric acid or 1/2 cup
lemon juice. Alternatively, sauté in oil.
Greens (kale, spinach, etc.)
Select young, tender greens. Wash. Trim leaves.
Water blanch 2 min
Herbs
Wash. Snip or leave on stalks.
For basil only, water or steam blanch 1 min. For
other herbs, blanching is not necessary. Freeze in a
single layer on baking sheet lined with wax paper;
transfer to containers when fully frozen.
Kohlrabi
Select tender, mature stems. Trim ends and peel off
tough bark. Wash. Slice tender centers crosswise,
1/4 inch thick. Leave small roots whole.
Water blanch slices for 2 min, stems for 3 min.
Mushrooms
Wipe with damp paper towel. Trim hard tips of
stems. Sort by size; cut large mushrooms.
May be frozen without blanching. Or, blanch
whole, 5 min; quarters, 3 1/2 min; slices, 3 min.
Or, sauté mushrooms in butter or margarine and
cool quickly.
Okra
Wash. Separate pods 4 inches and shorter from
longer pods. Remove stems.
Water blanch small pods 3 min, large pods 4 min.
Onions, green onions, leeks
• For onions, remove peel and chop.
• For green onions, trim ends, then slice or
leave whole.
• For leeks, make a cut through leaves and bulb. Do
not cut roots. Wash thoroughly.Trim tops. Leave
whole or slice.
May be frozen without blanching. Bag and freeze.
For best odor protection, wrap onions in plastic
warp before putting in bags.
Peas, garden/snow/sugar
Shell garden peas. No need to shell snow or sugar
peas.
Water blanch 1 1/2 min
Water blanch 3 min
Steam blanch 4 min
Steam blanch 3 min
Steam blanch 2 1/2 min
(Continued)
Guide E-320 • Page 3
Table 1. Freezing Techniques for Vegetables (cont.)
Vegetable
Preparation
Blanching Times and Freezing Techniques
Peppers, green/red/sweet/hot
Wash, remove stems and seeds.
Freeze whole, or cut as desired; no blanching
needed. (See NMSU Extension Guide E-311,
Freezing Green Chile [http://aces.nmsu.edu/
pubs/_e/E311.pdf ].)
Potatoes and Jerusalem artichokes
Wash. Peel, cut, or grate as desired. Either cook
in water or sauté grated potatoes in oil. Grated
potatoes for hash browns and mashed potatoes
freeze well.
For new potatoes, water blanch whole potatoes
5 min, pieces 2–3 min.
Sweet potatoes
Wash and dry.
Bake just until tender, then cool, peel, and cut.
Pack in flat layers or roll in lemon juice and brown
sugar. Or, purée with orange juice.
Tomatoes, red and green
Wash and dip in boiling water for 30 seconds to
loosen skins.
Core and peel. Freeze whole or in pieces. Pack into
containers.
Winter squash/spaghetti squash/pumpkin
Wash and remove seeds.
Bake whole or cut in half. Place cut side down on
baking sheet. Cook until tender. Scrape pulp from
rind, or remove rind and cube. For pumpkin, cool
and cut into cubes, then freeze; or mash pulp, cool,
and pack.
Zucchini/summer squash
Wash, trim ends. Cut into slices or strips.
Water blanch 3 min or steam blanch 4 min and
freeze. Or, cover with breadcrumbs and sauté in oil.
Cool and freeze. For sautéed squash, place waxed
paper between slices before freezing.
Original author: Alice Jane Hendley, Food and
Nutrition Specialist. Subsequently revised by Martha
Archuleta, Food and Nutrition Specialist.
Nancy Flores is the Extension Food
Technology Specialist in the Department of Extension Family and Consumer Sciences at NMSU. She earned
her B.S. at NMSU, M.S. at the
University of Missouri, and Ph.D. at
Kansas State. Her Extension activities
focus on food safety, food processing,
and food technology.
Cindy Schlenker Davies is the
County Program Director and Extension Home Economist at NMSU’s
Bernalillo County Extension Office.
She earned her B.S. at Eastern New
Mexico University and her M.A. at
NMSU. Her Extension and public
outreach work focuses on food processing and preservation and food safety.
Contents of publications may be freely reproduced for educational purposes. All other rights reserved. For permission to use
publications for other purposes, contact pubs@nmsu.edu or the authors listed on the publication.
New Mexico State University is an equal opportunity/affirmative action employer and educator. NMSU and the U.S. Department
of Agriculture cooperating.
Revised August 2015
Las Cruces, NM
Guide E-320 • Page 4