Michigan State University Extension
Preserving Food Safely - 01600032
1/2 tsp. canning or pickling salt 1/4 tsp. powdered ascorbic acid
YIELD: About 2 half-pints
PROCEDURE: The pungency of fresh horseradish fades within 1 to 2 months, even when refrigerated. Therefore, make only small quantities at a time. Wash horseradish roots thoroughly and peel off brown outer skin. Peeled roots may be grated in a food processor or cut into small cubes and put through a food grinder. Combine ingredients and fill into sterile jars (see directions below for sterilizing jars) leaving 1/4-inch headspace. Seal jars tightly and store in a refrigerator.
To sterilize empty jars, put them right side up on the rack in a boiling-water canner. Fill the canner and jars with hot (not boiling) water to 1 inch above the tops of the jars. Boil 10 minutes at altitudes of less than 1000 ft. At higher elevations, boil 1 additional minute for each additional 1000 ft. elevation. Remove and drain sterilized jars one at a time.