
Horseradish sauce is a prepared condiment built on the grated root of horseradish (Armoracia rusticana) folded into a creamy or vinegared base.
Thick and creamy in texture, with a sharp, sinus-clearing pungency over a vinegared tang; the heat fades on the finish as the volatile oil dissipates, leaving a faint bitterness.
Bartenders spoon or stir a small amount into savoury, tomato-based builds as a pungent seasoning, working it in cold to preserve the volatile heat, since air and warmth blunt its sharpness. It is dosed sparingly and can also be streaked on a rim or garnish for aroma.
Where it is a background accent, another allyl-isothiocyanate source such as mustard or wasabi can stand in, with the creamy body rebuilt from sour cream, mayonnaise or yoghurt and the tang from vinegar or lemon; where its pungent-root character is the featured note, it is essentially not substitutable, as no unrelated ingredient reproduces that sharp mustard-oil heat.
Prepared horseradish
Prepared horseradish is grated root mixed only with vinegar and salt — sharp and unadulterated; horseradish sauce is that same base folded into cream, sour cream or mayonnaise, making it milder and richer. The names are often used loosely for one another.
Wasabi
Both derive their heat from allyl isothiocyanate and hit the sinuses almost identically, but wasabi comes from Eutrema japonicum while horseradish comes from Armoracia rusticana. Much commercial 'wasabi' is in fact dyed horseradish.
The sauce takes its bite from grated horseradish root: cutting the root releases the enzyme myrosinase, which converts the glucosinolate sinigrin into allyl isothiocyanate, the volatile "mustard oil" behind its sharpness. That compound is unstable, so prepared sauces are milder than fresh root; vinegar is added to stabilise the flavour and fix the pungency, while cream, sour cream or mayonnaise gives the sauce its body.
Its pungency is volatile and fades with exposure to air; keep the jar refrigerated and sealed, and expect it to darken, turn bitter and lose sharpness once opened.