Comparative Aroma Extract Dilution Analysis of Changes in Aroma Components of Seasoned Soy Sauce Prepared from Soy Sauce and Mirin during Heating

An investigation using Aroma Extract Dilution Analysis (AEDA) applied to the aroma concentrate of a model heated seasoned soy sauce, prepared from soy sauce and mirin, revealed 36 aroma peaks, and 32 compounds were identified or tentatively identified from the detected peaks. Among them, 3-(methylthio) propanal was the most dominant compound, showing the highest Flavor Dilution (FD) factor, followed by 4-hydroxy-2,5-dimethyl-3(2H)-furanone, 5(or 2)-ethyl-4-hydroxy-2(or 5)-methyl-3(2H)-furanone, and 3-hydroxy-4,5-dimethyl-2(5H)-furanone. While most of the identified compounds have already been reported, 2,3-dihydro-5-hydroxy-6-methyl-4(4H)-pyranone was identified in the seasoned soy sauce for the first time. A comparative AEDA study of the unheated and heated seasoned soy sauces revealed that approximately half of the aroma peaks were detected at FD factors that were 16-fold higher in the heated seasoned soy sauce, while the remainder showed equal or highly similar FD factors. This indicated that the heating history of the seasoned soy sauce as well as the materials employed are important in the aroma of heated seasoned soy sauce, and a limited number of aroma components are related to changes in the seasoned soy sauce aroma by heating. Finally, relative quantitative analysis of aroma active compounds, i.e., Strecker aldehydes, furanone/pyranones, and phenols, in the seasoned soy sauce heated for different times revealed that only a few components greatly increased during heating and these might be important for the changes in the seasoned soy sauce aromas with different heating times.