Changes in Volatile Compounds during Smoking Process and Evaluation of Major Aroma Constituents of Dried Bonito (Katuo-Bushi)

Abstract

In order to clarify major volatile compounds responsible for the aroma of the dried bonito (Katuo-bushi), volatile compounds produced in each smoking process (boiled bonito meat to katuobushi) were analyzed by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactmetry (GC-O). The volatile compounds identified in boiled bonito meat were aldehydes, ketones, furans, etc. These compounds increased or decreased during smoking process. Pyrazines, phenols and many other compounds did not appear until smoking process. Sulfur-containing compounds (dimethyl sulfide, dimethyl disulfide) showed little change through smoking process. Main odor in boiled bonito meat detected by GC-O provided sulfurous note due to sulfur-containing compounds (dimethyl sulfide etc.) and nutty note of unidentified compounds, probably due to very small amounts of pyrazines. As the smoking process proceeded roasty note of pyrazines and smoky note of phenols appeared and intensified. Sulfurous note derived from sulfur-containing compounds changed little throughout the smoking process. These changes induced in the smoking process will convert the aroma of boiled fish changed into that of dried bonito (Katuo-bushi). Consequently, some ethyl-dimethylpyrazines of roasty note and guaiacol and 4-methylguaiacol of smokey note were considered as main effective volatile compounds causing the aroma of the dried bonito (Katuo-bushi). The sulfur-containing compounds were also important, to develop strong and unique odor.