Volatile compounds in fermented and acid-hydrolyzed soy sauces

Volatile compounds in fermented and acid-hydrolyzed soy sauces were isolated and analyzed using solvent extraction and solid-phase microextraction. Quantitatively, alcohols and esters were dominant in the volatiles of fermented soy sauce, whereas heterocyclic compounds, including pyrazines and furans, and acids were relatively abundant in the acid-hydrolyzed soy sauce. The odor-active compounds were also evaluated. The major odor-active compounds of fermented soy sauce were acetic acid, furfuryl alcohol, 2-methoxyphenol, benzeneethanol, benzoic acid, butyric acid, 2-ethyl-4-hydroxy-5-methyl-3(2H) furanone, and 2-methylbutanal, whereas acetic acid, 2-methoxyphenol, formic acid, benzoic acid, 2,5-dimethylpyrazine, 2,6-dimethylpyrazine, butyric acid, 2,6-dimethoxyphenol, 3-hydroxy-2-methyl-4H-pyran-4-one, 2-acetyl-5-methylfuran, 2,5-dimethyl-3-ethylpyrazine, and 2-methylbutanal constituted the major odor-active compounds of acid-hydrolyzed soy sauce.