All vegetables contain enzymes that enable the vegetables to mature. Freezing slows this maturing, or aging, process but does not stop it. Blanching (scalding vegetables in boiling water or steam for a short time) stops the enzyme action that can cause loss of flavour, colour, and texture in frozen vegetables. Blanching also cleans the surface of the vegetables, brightens the colour, and softens the vegetables making them easier to pack for freezing.
Follow blanching times carefully. Underblanching encourages enzyme activity and is worse than not blanching at all. Overblanching results in loss of flavour, colour, and nutrients.
Use a blancher with blanching basket and lid, a pasta pot with fitted strainer and lid, or a large pot with a wire basket and lid.
Bring 1 - 2 gallons (4 - 8 L) water to a vigorous boil and leave over high heat throughout the blanching process. A large amount of water is used so the water will resume boiling quickly after the vegetables have been added. Do not add salt unless otherwise specified.
Blanch 2 cups of vegetables for every 1 gallon (4 L) of water. Place prepared vegetables in a basket or strainer and lower into vigorously boiling water. Cover pot with a lid.
Begin timing immediately (see SPECIFIC DIRECTIONS FOR FREEZING VEGETABLES for blanching times). Blanching water may be reused several times, adding more water as needed.
Some vegetables may be steam blanched.
Use a pot with a tight lid and a basket that holds vegetables above the water at the bottom of the pot.
Bring water to a vigorous boil with the lid on the pot. Leave pot over high heat throughout the
blanching process. Do not add salt unless otherwise specified.
Place only enough vegetables to form a single layer in the basket, so that the steam reaches all surfaces quickly. Place the basket in a pot over boiling water. Cover pot with a lid.
Begin timing immediately (see SPECIFIC DIRECTIONS FOR FREEZING VEGETABLES for blanching times).
Blanching water may be reused several times, adding more water as needed.