3,4-Dihydroxy-3-hexen-2,5-dione (DHHD) was identified in a thermally treate
d mixture of cysteamine and fructose. GC/MS and C-13-NMR measurements revea
led that its flavor activity is present only in the open chain form, while
the cyclic species was shown to be completely odorless. The flavor quality
of DHHD was similar to that of 4-hydroxy-2,5-dimethyl-3(2H)-furanone (furan
eol) and its odor threshold was determined to be 10 mug/l in sunflower oil.
NMR measurements, however, showed that the odor-active open chain tautomer
is present only in aprotic solvents, such as oils, while the cyclic, odorl
ess tautomer (diacetylformoin) is immediately formed in aqueous solution.