Fromthe vacuumdistilled volatiles ofshoyu, a neutral fraction was obtained. Shoyu was also directly extracted with dichloromethane and then the extract was separated into ten (A~J) fractions. The J fraction was a neutral one. The J fraction was further separated into twelve fractions by liquid column chromatography. All fractions obtained were analyzed by gas chromatography and combined gas chromatography-mass spectrometry. Consequently, 142 components were identified, 82 of which have not been reported previously as volatile constituents of shoyu. The identified compounds were 37 hydrocarbons, 22 alcohols, 22 carbonyls, 22 esters, 12furans, 6 sulfurous compounds, 1 pyrone, 5 phenols, 1 furanone, 1 acid, 1 lactone and 12 other compounds.Fromthe results of quantitative analysis and organoleptic evaluation, phenylacetaldehyde is considered to be most important in the neutral fraction.In the previous papers,1~5) the authors reported that 131 flavor components were identified in shoyu and that 4-hydroxy~2(or 5)-ethyl-5(or 2)-methyl-3(2i/)-furanone (abbreviated as HEMF,tautomers ratio: ca. 3 : 2) was the main and the most important constituent of the characteristic flavor of shoyu. In these Studies, the basic, acidic I, acidic II and neutral fractions were obtained from the vacuumdistilled volatiles ofshoyu, and the volatiles in the basic3) and acidic5} fractions have been investigated. It was also reported that the direct extract of shoyu with dichloromethane was separated into ten (A-J) fractions5) in order to cover the components that were not obtained by the above method. This work was concerned with the identification of many components in the uninvestigated fractions of shoyu; i.e. the volatile neutral fraction and the neutral J fraction from the direct extract with dichloromethane. Some components contributing to the odor of the neutral fraction were also discussed.
MATERIALS AND METHODSShoyu. Commercially available Japanese genuine fermented shoyu (pH 4.8) was used for the following experiments.Separation of a volatile shoyu flavor concentrate into acidic, basic and neutral fractions. Four fractions (basic, acidic I, acidic II and neutral) were obtained from the vacuumdistilled volatiles by the method described in the previous paper.5) All concentrations and pH adjustments were carried out at a temperature of below 50°C.Separation of a shoyu flavor concentrate (CH2Cl2 extract) into ten fractions. The direct dichloromethane extract, 19.5g, was obtained from 40 liters of shoyu. The extract was fractionated into ten (A~J) fractions by the method described in the previous papers.4'5] The A and B fractions were basic; the C~I fractions were acidic and the J fraction was neutral. All concentrations and pH adjustments were carried out at a temperature of below 50°C. The weight ratio of each fraction to total extract was calculated; the basic ones were 27%, the acidic ones were 57%and the neutral one was 16%.
