3P-17 PDF
Non-targeted Metabolomics of Rice Koji with MALDI-IMS
In the field, rice koji quality is determined by experienced sake makers based on visual and structure. Recently, there is rising interest for understanding this attribute scientifically to aid in more effective quality control. While non-targeted metabolomics is an appropriate approach to address this demand, conventional methods using GC-MS or LC-MS cannot visualize distribution of potential metabolites related to koji structure. Matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI-IMS) is considered to overcome this problem. However, since rice koji is a new sample in this field, it is important to develop suitable methods to perform non-targeted analysis of koji as novel application field of MALDI-IMS.
This study focused on sample preparation and matrix application to obtain clear and informative visualization. We found that several factors such as cutting temperature and section thickness, as well as aiding tools to facilitate smooth sectioning were very important to acquire a good quality section. We also performed a preliminary analysis by comparing materials related to koji production such as polished rice and steamed rice to discover interesting compounds from rice koji. One peak at m/z 104.1, later identified as choline, was found to have high intensity and was spread across the koji section.