Improvement of fish sauce flavor by Eurotium herbariorum

Volatile compounds of various commercial fish sauces were collected by a purge-and-trap method and analyzed by gas chromatography (GC) and GC-mass spectrometry. A large amount of dimethyl disulfide (DMDS) and the branched short-chain aldehydes such as 2-methylpropanal, 2-and 3-methylbutanal, with low odor threshold values, were detected in Ika-ishiru (fish sauce made from Japanese common squid internal organs). These compounds increased with the storage of Ika-ishiru and a stinging odor developed. The effects of Eurotium herbariorum on DMDS and aldehyde development in Ika-ishiru were examined. The fungus apparently decomposed aldehydes and DMDS in Ika-ishiru, and changed most of authentic aldehydes into their corresponding alcohols and acids. The lower the abundance of these compounds, the more a desirable aroma developed in Ika-ishiru. Because the free amino acid compositions did not change before or after the treatment with the fungus, it was found to be desirable for the improvement of fish sauce flavor.