Allys isothiocyanate (FEMA# 2034, CAS# 57-06-7; mustard oil) is a colorless oil that is responsible for the pungent taste of mustard, horseradish and wasabi. It is found in mustard, horseradish, cabbage, sauerkraut, milk, beans, cauliflower, and Brussels sprouts. It has a stinging, sulfuric, mustard odor and pungent, sharp, characteristic mustardlike flavor; on dilution it possesses a vegetable note.
Allyl isothiocyanate is naturally produced by hydrolysis of natural rhizome thioglucosides, which are conjugates of the sugar glucose and sulfur-containing organic compounds. This hydrolysis is catalyzed by the enzyme myrosinase, which is capable of hydrolyzing glucosinolates. The hydrolysis occurs when the enzyme is released on cell rupture caused by the maceration of the plant’s rhizome. An example in which sinigrin (CAS# 3952-98- 5) is hydrolyzed into allyl isothiocyanate and its isomer, 1-cyano-2,3-epithiopropane (CAS# 58130-93-1) is shown (F-2).
The unique fl avor of wasabi, for example, is a result of complex chemical mixtures from the broken cells of the rhizome, including those resulting from the hydrolysis— glucose and other methylthioalkyl isothiocyanates (F-3). Additional examples of isothiocyanates used in fl avors can be seen in F-4.