Many of the low molecular compounds in fermented food are
odor and taste-active and they constitute the flavor. Sake is a Japanese
traditional alcoholic beverage which is produced by simultaneous
saccharification and alcohol fermentation of polished and
steamed rice by Aspergillus oryzae and Saccharomyces cerevisiae (1).
This multiple parallel fermentation process is unique to sake
brewing and generates various low molecular weight compounds
that constitute the complex flavor of sake. A recent study on sensory
analysis arranged flavor terminology system with 86 terms
representing the attributes independently perceivable in sake (2).
Recently, the declining domestic consumption has become a
serious problem in sake industry thus, there is an ever-increasing
interest and challenge to increase the variety of sake to stimulate
enthusiasm among consumers (3). For example, sake that is rich in
fragrance was made by breeding isoamyl acetate/ethyl caproatehigh
producing yeasts (4,5), while yeasts which have different
productivities of organic acids (an important components of taste)
have also been bred (6,7). However, information about the relationship
between the flavor characteristics and the components
necessary for these studies is limited. Moreover, because the
amount of export has been increasing for the last decade, a method
capable of objectively evaluating the flavor of sake is required.
A lot of effort in the 20th century has focused on the identifi-
cation of 300 compounds in sake, as well as the contribution of
individual components to sake flavor (8e10). However, there are
many attributes of sake that cannot be explained by chemical
compounds. Nowadays, there has been a growing interest in
metabolomics which can detect complex biological changes by
examining variation in total metabolite profiles (11,12). In fact, the
comprehensive approach of metabolomics has been effectively
applied to explain the differences in quality of food samples
(13e15).