Freezing is an excellent way to preserve fresh vegetables. The quality of frozen vegetables depends on the quality of the fresh products and how they are handled from the time they are picked until they are ready to eat. It is important to get the product from the Garden to the freezer in as short a time as possible. It is important, also, to start with high-quality vegetables, as freezing will not improve the product’s quality.
Blanching and prompt cooling are necessary steps in preparing practically every vegetable, except herbs and green peppers, for freezing. The reason is that heating slows or stops the enzyme action. Enzymes help vegetables grow and mature. After maturation, however, they cause loss of quality, flavor, color, texture and nutrients. If vegetables are not heated enough, the enzymes continue to be active during frozen storage and may cause the vegetables to toughen or develop off-flavors and colors. Blanching also wilts or softens vegetables, making them easier to pack. It destroys some bacteria and helps remove any surface dirt.
Selecting Freezing Containers
Select containers best suited to the vegetable. Square or rectangular flat-sided containers make the best use of freezer space. Good quality moisture- and vapor-proof packaging materials made of glass or rigid plastic are best. They prevent drying of the food during freezer storage. Moisture- and vapor-resistant bags and waxed cartons designed for freezing also retain satisfactory quality.
Selecting and Preparing Vegetables
Use vegetables at peak flavor and texture. When possible, harvest in the cool part of the morning and freeze within two hours. Wash vegetables thoroughly in cold water, lifting them out of the water as grit settles to the bottom of the washing container. Sort by size for blanching and packing.
Most vegetables may be blanched in boiling water or steam.
Blanching in Boiling Water
To blanch vegetables in boiling water, bring at least 1 gallon of water to a rapid boil in a blancher or large kettle with a lid. Lower a pound of prepared vegetables placed in a metal basket or cheesecloth bag into the boiling water and cover with a lid. Start counting time as soon as the vegetables are in the boiling water. Keep heat on high for the total blanching time.
Follow the recommended blanching time for each vegetable. Under blanching may stimulate enzyme activity and could be worse than no blanching. Prolonged blanching causes a loss of vitamins, minerals, flavor and color.
Heating in steam is another way to blanch vegetables. Steam blanching takes somewhat longer than water blanching but helps retain water-soluble vitamins.
To steam vegetables, bring 1 to 2 inches of water to a rolling boil in a kettle with a tight-fitting lid and a rack that holds a steaming basket or cheesecloth bag at least 3 inches above the bottom of the kettle. Put a single layer of vegetables in the basket or bag so steam can reach all parts quickly. Place the basket or bag on the rack in the kettle, cover and keep heat on high. Start counting steaming time as soon as the lid is on.
Other ways to heat particular foods before freezing include heating pumpkin, sweet potatoes and winter squash in a pressure cooker or oven; heating mushrooms in fat in a fry pan; and simmering tomatoes on a range.
After vegetables are heated, cool quickly and thoroughly to stop the cooking. To cool vegetables heated in boiling water or steam, plunge the basket of vegetables immediately into a large quantity of cold water that is 60 degrees Fahrenheit or below. Change water frequently or use cold running or iced water. Use about 1 pound of ice for each pound of vegetables. It takes about as long to cool the food as to heat it. When vegetables are cooled, remove from the water and drain thoroughly.
There are two basic packing methods recommended for frozen vegetables: dry pack and tray pack.
To dry pack, place the blanched and drained vegetables into meal-sized freezer bags or containers. Pack tightly to cut down on the amount of air in the package. Leave 1/2-inch head space at the top of rigid containers and close securely. For freezer bags, fill to within 3 inches of top, twist and fold back top of bag, and tie with a twist tape or rubber band about 1/2- to 3/4-inch from the food. This allows space for the food to expand. Provision for head space is not necessary for foods such as broccoli, asparagus and Brussels sprouts that do not pack tightly in containers.
To tray pack, place chilled, well-drained vegetables in a single layer on shallow trays or pans. Place in freezer until firm, then remove and quickly fill labeled bags or containers. Close and freeze immediately. Tray-packed foods do not freeze in a block but remain loose so that the amount needed can be poured from the container and the package closed.
Labeling and Storing
Label packages with the name of the product and the freezing date. Freeze at once at 0 degrees Fahrenheit or lower. Because speed in freezing is important for best quality, put only as much unfrozen vegetables into the freezer at one time as will freeze in 24 hours, usually 2 to 3 pounds per cubic foot of freezer capacity.
For quickest freezing, place packages at least 1 inch apart against freezer plates or coils. After vegetables are frozen, rearrange packages and store close together. Most vegetables maintain high quality for 12 to 18 months at 0 degrees Fahrenheit or lower. Longer storage will not make food unfit for use, but may impair quality.
It is a good idea to post a list of the frozen vegetables near the freezer and to check off packages as they are used.