Effects of Drying Methods During “<i>Karebushi</i>” Manufacturing Process on Flavor Compounds

Abstract

This study examined the effects of drying methods on the generation of flavor compounds in Karebushi. First, in order to obtain the primary mold culture product, Eurotium repens (YM-1418) was sprayed on the surface of Hadakabushi and cultured for two weeks. The samples were then dried either under the sun or by a machine (dehydrator). Subsequently, the samples were cultured for another week to produce a secondary mold culture product. The flavor compounds of samples were analyzed using GC-MS. Forty major flavor compounds were identified, and among these compounds, hexanal, heptanal, and octanal were quantified. Results indicated that the different drying methods led to the generation of different flavor compounds, especially of aldehydes. Furthermore, in comparing the sun-drying and machine-drying methods, the former increased hexanal and heptanal, and the extent of these increases was proportional to the duration of sun-drying. We also identified that the production of these aldehydes increased when drying during spring and summer. Next, the increase of these aldehydes was clarified by the UV irradiation test. We revealed that the sun's UV rays were mainly responsible for the remarkable increase in hexanal and heptanal during the Karebushi manufacturing process.