Brief boiling, called blanching, softens crisp cabbage while improving the color and tenderness of the leaves. Cabbage requires blanching before you can freeze it because the process slows flavor and color loss. Blanching also makes the leaves easier to handle when you are making cabbage rolls or other recipes that require whole leaves. The leaves develop a brighter color and wrap more easily around the filling after a short dunk it the boiling water.
Remove the outer leaves from the cabbage head and dispose of them. Cut heads into wedges or a coarse shred for freezing, or remove the individual leaves whole for using in cabbage rolls and wraps.
Fill a large pot with water and bring it to a boil. Set a bowl of ice water near the cooking area.
Add up to 1 pound of cabbage wedges or shredded cabbage to the boiling water. Boil wedges for 3 minutes and shredded cabbage for 1 ½ minutes. Use tongs to hold whole cabbage leaves and submerge them individually in the water for only 30 seconds, or just until they begin to wilt.
Remove the cabbage from the water, using a slotted spoon if necessary, and immediately submerge the cabbage in the ice water. Add more ice, if necessary, and allow the cabbage to cool completely.
Drain the cabbage and pat the leaves dry with a towel. Use immediately or transfer to a freezer-safe storage container and store in a 0-degree Fahrenheit freezer for up to 12 months.