Although corn may be preserved by a variety of methods, the convenience of ready-to-use canned corn makes it worthwhile to spend the time pressure-canning it.

Corn is a low-acid food and for safety reasons it must be processed in a pressure canner at specified times and pressures. It is not safe to process corn in a boiling water bath even if it is boiled for several hours. Boiling water never gets above 212 F; the temperature inside a vented pressure canner at 10 pounds (weighted gauge) or 11 pounds (dial gauge) canner is 240 F and is adequate to kill botulism spores.

The exception to pressure-canning corn is when corn is acidified with vinegar to make pickled corn relish. If you do not have a pressure canner, freeze the corn or prepare some jars of pickled corn relish, which can be processed in a boiling water or atmospheric steam canner.

Preserve corn as soon after harvesting as possible. The corn will be best if canned within six hours of being picked. Select tender ears of corn with milky kernels — corn that is ideal for eating fresh. After husking and removing the silk, trim off the ends of the ears to remove small fibrous kernels. Wash corn before blanching.

To prepare whole-kernel or cream-style corn for canning, blanch ears 4 minutes. Cool ears and cut kernels from the cob. For whole-kernel corn, cut kernels from the cob at three-fourths of their depth. Do not scrape the cob. For cream-style corn, cut kernels from the cob at two-thirds their depth and scrape the cob with a knife to remove remaining kernels; combine scrapings with the half-kernels.

Canning directions differ based on style of cut, size of jars, added liquid, and processing time. Whole-kernel corn may be canned in pints or quarts. The high starch content of corn causes it to expand during processing. Pack corn loosely in the jar and allow 1 inch of head space.

To raw pack corn, put whole-kernel corn in jars and cover with boiling water. For hot packs, add 1 cup of hot water for each quart of whole kernel corn, bring to a boil, and simmer 5 minutes. Fill jars with hot corn and cooking liquid. Salt is an optional ingredient in canned corn.

If desired, add 1 teaspoon salt per quart or 1/2 teaspoon salt per pint. Wipe rims of jars with a clean, damp, paper towel, add lids, and tighten screw bands. Process pints of whole-kernel corn for 55 minutes, and quarts for 85 minutes, in a weighted-gauge canner at 10 pounds pressure at altitudes of 1,000 feet or below or in a dial-gauge canner at 11 pounds pressure at altitudes up to 2,000 feet.

In a weighted-gauge canner, increase pressure to 15 pounds at altitudes above 1,000 feet. In a dial-gauge canner increase pressure to 12 pounds between 2,001-4,000 feet, 13 pounds between 4,001-6,000 feet, and 14 pounds between 6,001-8,000 feet.

Because of its increased density, cream-style corn must be packed in half-pint or pint jars only. Hot pack cream-style corn by adding 1 cup boiling water to each 2 cups of corn. Heat to a boil and simmer 3 minutes before packing the hot corn into jars, leaving 1 inch of head space. Process pints or half-pints of cream-style corn for 85 minutes. The long processing time is necessary because of the density of the product.

Remember these points about pressure-canning: Exhaust steam from the canner for 10 minutes before adding the weight or pressure regulator. The process time begins when the desired pressure is reached. Regulate heat to maintain the desired pressure. If pressure goes below the specified pounds, start processing time over. When processing time is complete, remove canner from heat. Do not force cool the canner — allow to air cool naturally. When canner reaches 0 pounds (fully depressurized), remove weight or pressure regulator and wait 10 more minutes to remove canner lid and jars.

Some of the sweeter varieties of corn may turn brown during processing because the very high temperature in the pressure canner may cause the natural sugars in the corn to caramelize. Browning does not affect the safety of the product.

If you have food preservation questions, a home economist is available to answer questions on Wednesdays from 10 a.m. to 2 p.m., by calling 717-394-6851 or writing Penn State Extension, Lancaster County, 1383 Arcadia Road, Room 140, Lancaster, PA 17601.

The Well Preserved news column is prepared by Penn State Extension.

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