By starting from scratch, you can make sure that your horseradish packs a lasting punch.
Buying prepared horseradish is convenient, but making your own produces better flavor and offers more control.
We figured out a way to ensure that our homemade version packs a wallop and—because the potency of shredded horseradish wanes over time—retains that punch for several weeks.
We do this by adding a small amount of vinegar and warm water to the horseradish when we process it and then adding more vinegar after a 10-minute rest. Here's why the approach works: When you break the cells of horseradish, they release an enzyme called myrosinase, which reacts with another compound to form the pungent chemical allyl isothiocyanate. More isothiocyanate will form if the solution is slightly acidic, hence the small addition of vinegar at the initial blending; like most chemical reactions, this process is hastened by heat, thus the warm water. The 10-minute rest allows the pungency to build, and the final addition of vinegar stabilizes the level of punch, so it is retained over time.
METHOD: Process 5 ounces peeled, chopped horseradish (1 cup) with ½ cup warm water and 1 teaspoon distilled white vinegar in blender until horseradish is as fine as it will get, about 1 minute. Let mixture sit in blender for 10 minutes, then add ½ teaspoon table salt and additional 4 teaspoons vinegar. Blend until combined. Transfer to airtight container and refrigerate for up to 3 weeks.