University of Missouri Extension

GH1503, Reviewed June 2003

Quality for Keeps: Freezing Vegetables

Barbara J. Willenberg
Associate State Food and Nutrition Specialist
Department of Food Science and Human Nutrition

Frozen foods can add variety to your meals year-round. As with any method of food preservation, following specific guidelines will assure you of high quality, safe food. For additional information, refer to other Human Environmental Sciences guides in the Quality for Keeps freezer series.

Blanching

Blanching, or scalding vegetables in boiling water or steam for a short period of time, is a must for almost all vegetables to be frozen except onions and green peppers. It slows or stops the action of enzymes. Up until harvest time, enzymes cause vegetables to grow and mature. If vegetables are not blanched, or not blanched long enough, the enzymes continue to be active during frozen storage causing off-colors, off-flavors and toughening.

In addition, blanching cleanses the surface of dirt and spoilage organisms, brightens the color and helps retard loss of vitamins. It also wilts or softens vegetables and makes them easier to pack.

Blanching time is crucial and varies with the vegetable and size of the pieces to be frozen. Under-blanching speeds up the activity of enzymes and is worse than no blanching. Over-blanching causes loss of flavor, color, vitamins and minerals. Follow recommended blanching times for specific vegetables.

Cooling

As soon as blanching is complete, cool vegetables quickly and thoroughly to stop the cooking process. To cool, plunge the basket of vegetables immediately into a large quantity of cold water. Change water frequently or use cold running water or iced water. If ice is used, about one pound of ice for each pound of vegetable is needed. Cool vegetables for the same amount of time as they are blanched. Drain vegetables thoroughly after cooling. Extra moisture can cause a loss of quality when vegetables are frozen.

Thawing and using

Follow the guidelines below to keep frozen vegetables safe and preserve their color, flavor, texture and nutritive value:

Other methods of cooking frozen vegetables include steaming, stir frying, pressure cooking or microwaving. Frozen vegetables can be added without thawing to soups or stews. Add them near the end of cooking to prevent texture loss. Many frozen vegetables can be baked in a covered, greased casserole in the oven. Partially thaw and separate pieces first. Although baking time for frozen vegetables varies, the approximate time for baking most partially thawed vegetables is 45 minutes at 350 degrees Fahrenheit. This is not a time- or energy-efficient method, however, unless other foods are being baked in the oven at the same time.

Freezing instructions for specific vegetables

Water blanch diced pieces or strips 2 minutes in 1 gallon of boiling water containing 4-1/2 teaspoons citric acid or 1/2 cup lemon juice. One-third-inch slices should be blanched for 4 minutes. Cool, drain, package, seal and freeze.

Note
Slices to be fried should be packed between sheets of freezer wrap for easy removal.

Note
Do not steam blanch greens.

Note
Small pumpkins can be pierced and baked whole on a tray in an oven or microwave oven until soft. After cooling, peel, remove strings and seeds and mash. Package, seal and freeze.

Table 1
Approximate yield of frozen vegetables from fresh

*As defined by the Missouri Department of Agriculture.

Table 2
Timetable for cooking frozen vegetables**

Time to cook after water returns to a boil.

**Use 1/2 cup lightly salted water for each pint (2 cups) of vegetables with these exceptions: lima beans, 1 cup; corn-on-the-cob, water to cover.

Tips for successful freezing

Types of packs

 

GH1503 Quality for Keeps: Freezing Vegetables | University of Missouri Extension

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