Vegetables that aren't typically stored in the freezer, such as celery and onions, become limp and soggy when frozen improperly. These vegetables undergo a texture change when frozen so they are typically refrigerated for fresh use. Freezing celery and onions does provide a long-term storage option if you use the thawed vegetables in cooked dishes such as a soups or casseroles. The vegetables retain their flavour and the texture loss isn't noticeable after cooking.
Wash the celery in cool water. Choose crisp stalks with few strings for freezing because limp or tough celery doesn't withstand freezing well.
Cut the celery into 1/2-inch or longer pieces. Alter the length of the pieces as necessary, depending on the size of pieces you plan to use in future dishes.
Bring a pot of water to a full boil. Drop the celery pieces in the boiling water, adding no more than 0.227kg. of celery at one time.
Boil the celery for 3 minutes. Remove the celery from the water with a slotted spoon and place it in a bowl of ice water to stop the cooking process.
Drain the celery in a colander. Pat the celery surface dry with a clean paper towel.
Measure 1/2-cup portions of the prepared celery. Wrap the portions in freezer wrap. Place the wrapped packages in a freezer storage bag and remove as much air as possible by pressing down on the bag while sealing. Freeze immediately.
Wash the onion in cool water. Peel the outer skin off the bulb.
Cut the onion into the desired size pieces for using in future recipes. Both diced onions and rings freeze well.
Place 1/2-cup portions into small freezer bags. Press the air out of the bags and seal closed.
Lay the bags in the freezer. Laying the bags flat hastens freezing.
Store frozen celery for up to six months. Onions are best used within six weeks but retain some of their flavour for up to six months.