Blanching -- boiling vegetables for a specified length of time -- is a simple but necessary task for freezing asparagus successfully. Like all vegetables, asparagus contains enzymes that ensure the asparagus plants mature and develop properly. Without blanching to stop the enzymes, the enzymes remain active, and the flavor, texture, color and nutritional content of the asparagus will be compromised. When properly blanched and packaged, asparagus retains its quality in the freezer for 10 to 12 months.
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Wash the asparagus under running water. Alternatively, fill a large bowl with cold water, then clean the asparagus by swishing it in the water. This method works best if the asparagus is dirty, as swishing it in water removes sand embedded in the tips of the asparagus spears.
Sort the asparagus into batches of small, medium and large spears, as larger spears require more blanching time than small, slender spears. Blanch and pack each size separately. Spears measuring more than 1/2 inch in diameter are considered to be large spears. Small spears are thin and have a diameter smaller than a pencil.
Cut large spears into 1- to 2-inch lengths. You can cut smaller spears or leave them whole.
Bring a large kettle of water to a full boil. Use 1 gallon of water for each 1 lb. of asparagus.
Place the asparagus in a metal basket or steamer. Immerse the basket immediately in the boiling water.
Cover the kettle securely. Set your kitchen timer as soon as the water returns to a boil.
Blanch small spears for 2 minutes, medium spears for 3 minutes and large spears for 4 minutes
Fill a bowl with ice water. When the timer rings, quickly remove the strainer from the kettle, then plunge the asparagus in the ice water. Allow the asparagus to cool rapidly, adding extra ice if necessary. Cooling time is about the same as blanching time.
Drain the cooled asparagus thoroughly. Pack the asparagus in resealable freezer bags or airtight plastic containers.