The pungency of fresh horseradish doesn’t seem to last. Grated right away, it tastes stronger than the prepared stuff in a jar, but over time its flavor fades. Is there a way to preserve that complex heat?
The flavor of the fresh horseradish root is far more vibrant and complex than the jarred stuff.
To see if we noticed the flavor fading, we grated the fresh root and tasted it plain and in tomato juice after two hours, four hours, and overnight. Like you, we found that the more time passed, the milder the flavor.
We did some research and learned that when horseradish is grated (or otherwise cut), its cells rupture, releasing an enzyme known as myrosinase. This enzyme rapidly reacts with another compound to form allyl isothiocyanate, the chemical that provides horseradish with its characteristic punch. But that sharpness is short-lived: Left unchecked, the enzymatic reaction quickly exhausts itself and the condiment loses pungency. We’ve found that commercial prepared horseradish, on the other hand, can last for weeks in the refrigerator without losing its punch. It turns out that the key is the vinegar it’s steeped in. The acetic acid preserves the root’s heat by slowing down the activity of the myrosinase, resulting in a more constant and gradual production of the potent compound allyl isothiocyanate. The upshot: more robust, longer-lasting pungency.
To make the best fresh horseradish and keep it spicy: Once you’ve grated your fresh horseradish, add some vinegar. For an 8- to 10-inch-long horseradish root finely grated on a rasp-style grater (peel it first), add 6 tablespoons of water, 3 tablespoons of white vinegar, and ½ teaspoon of salt. Refrigerated in an airtight container, the mixture will hold the heat for up to two weeks.