In soups and casseroles, celeriac adds mild flavor, or you can roast or fry it just as you would a potato or carrot. Although it stores well for several weeks in the pantry, you can extend the storage time by blanching and freezing diced or grated celeriac. The white root will oxidize and turn brown if you freeze it unless you take the time to blanch it and treat it with acidic lemon juice to slow down the enzymes that cause discoloration. Frozen celeriac loses its crisp texture so use it in soups, stews and casseroles.
Peel the outer skin off the celeriac root with a vegetable peeler. Trim off the roots and shoots. Cut the remaining root bulb into 1-inch cubes or grate it using the large holes on a vegetable grater.
Bring a pot of water to a full boil using 1 gallon of water per pound of celeriac. Add 1 tablespoon of lemon juice per gallon of water to help prevent the celeriac from browning or discoloring during storage.
Fill a large bowl with ice water as the water comes to a boil. Set the bowl near the pot.
Place the prepared celeriac root in a blanching basket. Submerge the basket in the boiling water for 3 minutes if the celeriac is cubed or 1 minute for cubed celeriac.
Lift the basket from the water and allow the moisture to drain back into the pot. Submerge the basket in the ice water for 1 to 3 minutes or until the celeriac is completely cool. The ice water stops the cooking process so the celeriac doesn't become mushy.
Drain the ice water from the celeriac. Blot it completely dry with a paper towel.
Label a freezer storage bag with the contents and the date on which you are freezing it. Fill the bag to within 1 inch of the seal with the blanched celeriac. Press out any excess air and seal the bag closed.
Freeze the celeriac immediately in a 0-degrees Fahrenheit freezer. Store the celeriac frozen for up to 1 month.
Keep frozen celeriac sealed tightly at all times, or it may absorb flavors and odors from other food in the freezer.
Add the frozen celeriac to soups or other dishes before cooking. You don't have to thaw the celeriac before adding it to the recipe.