Asparagus: Canning, Freezing, Pickling

Selection

Start by selecting young tender spears that are firm, straight, uniformly sized, and with closed, compact tips. If you grow your own asparagus, harvest spears when they are 4 to 10 inches (10 to 25 cm) long. Harvest spears at least every other day to prevent spears from becoming fibrous. It is best to cut asparagus spears below the soil level. Discontinue harvest when spear diameter becomes less than ⅜ of an inch (10 mm).

White or blanched asparagus is grown by shading the spears with mounds of soil or mulch so that sunlight never reaches the plant. White asparagus is more fibrous than green asparagus and has a stronger, slightly bitter flavor.

Storage of Fresh Asparagus

Keep fresh asparagus cold to preserve its tenderness and natural sweetness. Asparagus is best eaten or preserved the day it is purchased or harvested, but will keep up to 3 days if refrigerated. Wrap it in a damp cloth and store it in a perforated plastic bag in the refrigerator. Some people prefer to place bundled stalks upright in 1 inch (2.5 cm) of water in a glass or measuring cup in the refrigerator.

Preparing Asparagus

• Wash thoroughly.
• Sort by size.
• Snap off or trim at least ½ inch from the bottom of each spear.
• Remove scales with a sharp knife.

Freezing

• Cut into even lengths to fit containers.
• Water blanch small spears for 2 minutes, medium spears for 3 minutes, and large spears for 4 minutes. Reduce blanching time for shorter pieces.
• Cool promptly in cold water or ice water, drain thoroughly, and pat dry.
• Package in plastic freezer bags, freezer jars, plastic freezer boxes, or vacuum package. No headspace is necessary. Seal and freeze.
• Spears of asparagus may also be individually frozen before being packaged; this prevents freezing as one mass.

In its fresh state, asparagus has a high water content. As it freezes, the water changes to ice crystals, causing the cells to break down. As a result, frozen asparagus may seem less firm than other frozen vegetables.

Canning

Asparagus is a low-acid vegetable and must be processed in a pressure canner to be safe.

To can asparagus, prepare the asparagus as described above and follow guidelines from the National Center for Home Food Preservation for hot or raw packing. The long processing time and high temperature produce a softer product than fresh asparagus.

Pickled Asparagus

Many recipes for pickled asparagus are available in magazines and on the internet, but keep in mind not all have been research-tested. Pickled products will only be safe if enough vinegar has been added to increase the acidity to a safe level. For a research-tested recipe, try Pickled Asparagus from So Easy to Preserve and the National Center for Home Food Preservation.

Note: the amount of asparagus called for in these recipes allows you to cut off the desired length in order to have nice stems with pretty tips. Leftover stem pieces can be cut and stewed to serve as a vegetable or can be blanched for freezing.

Some additional tips when canning pickled asparagus include:

• Pack asparagus loosely so that adequate vinegar is in the jar.
• Avoid adding large amounts of other low-acid flavoring ingredients such as onion, garlic, and peppers.
• Make sure to use vinegar of 5% acidity.
• Process in a boiling water bath or atmospheric steam canner for safety according to guidelines. Processing is essential for the safety of the product.

The high salt concentration in this recipe will cause the asparagus to shrivel at first, but will plump up as it sits. The asparagus will float at first, but then will settle a little.

References

Andress, E.L. & Harrison, J.A. (2020). So Easy to Preserve. University of Georgia Cooperative Extension.

Hirneisen, A., LaBorde, L., McDonald, S., McGeehan, N., Reed, S., & Zepp, M. (2022). Preserving Food at Home Resource Guide. Penn State Extension.

LaBorde, L., Zepp, M., & Hirneisen, A. (2023, June 8) Let's Preserve: Freezing Vegetables, Penn State Extension.

The National Center for Home Food Preservation. University of Georgia.