Visualization of Phospholipids and Glucose in Rice Koji Using Microscopic Mass Spectrometry Imaging

Introduction

Rice koji is one of the most critical elements in sake brewing. Its main role in sake brewing is thought to be the supply of digestive enzymes which decompose starch and proteins. It is also well known that the composition of the finished rice koji has a large influence on sake quality (taste and aroma). Until now, however, evaluation of the quality of rice koji have often depended on the experience of the chief brewer. This suggests that scientific knowledge is insufficient, and there is still room for development in this area.v When the chief brewer evaluates the quality of rice koji, the physical structure of the koji, that is, its external appearance and texture, seems to be an index of quality. In past research, the internal structure of rice koji was investigated using the scanning electron microscope, but until recent years, little progress has been made in research on evaluating the relationship between the structure and composition of rice koji. Because the Shimadzu iMScope imaging mass microscope enables simultaneous observation of the structure and component distribution of samples, in this Application Note, we applied the iMScope to the field of fermentation, and attempted to visualize the structure and component distribution of rice koji.

April 1, 2021 GMT