Non-Targeted Analysis of Metabolites in Sake by using Gas Chromatograph - Time-of-Flight Mass Spectrometer (GC-TOFMS)
Introduction
Sake is a Japanese alcoholic beverage made primarily from rice, kome-koji, and water. In addition to alcohol, sake contains amino acids, organic acids, and sugars, which produce a variety of flavors and tastes. Sake is also classified as ‘Daiginjo-shu’, 'Junmai-shu’, and 'Honjozo-shu’, depending on the rice polishing ratio and whether or not distilled alcohol is added and other types of sake are classified as 'futsu-shu’1). Amino acids, organic acids, and sugars in sake are thought to originate from the metabolism of microorganisms such as kome-koji and yeast. Therefore, it may be possible to classify these types of sake by metabolomic analysis.
Gas chromatograph-mass spectrometer (GC-MS) is widely used for metabolomics due to their rich database, easy operation, and high reproducibility of measurements. Measurement targets of GC-MS are volatile compounds. However, derivatization processes such as trimethylsilylation can be used to measure highly polar metabolites like sugars and amino acids. Additionally, in the field of metabolomics, "unknown compounds" that are not registered in the library database (DB) are sometimes detected. In this case, the molecular formula of even an unknown compounds can be determined by using a time-of-flight mass spectrometer (TOFMS) as a mass spectrometer and performing an "integrated analysis" that combines electron ionization and soft ionization2). Furthermore, by using automated structure analysis software named “msFineAnalysis AI” which uses artificial intelligence (AI) to predict EI mass spectra from chemical structures, it is possible to estimate the structural formula3).
In this MSTips, we will report the results of non-targeted analysis of metabolites in sake using gas chromatograph time-of-flight mass spectrometry (GC-TOFMS).