A traditional Japanese alcoholic beverage, sake, contains several oligosaccharides, which are associated with the taste of sake; however, little is known about the specific molecular species and concentrations of oligosaccharides in sake. Here, we developed an analytical method using hydrophilic interaction liquid chromatography time-of-flight/mass spectrometry (HILIC-TOF/MS) which successfully detects the oligosaccharides in sake. A series of oligosaccharides with successive degree of polymerization (DP) values up to 18 were identified in sake for the first time, which we have named sake oligosaccharides (SAOs). The concentrations of the SAOs with DP = 3-8 were estimated to be in the range of 200-2000 ppm. Quantitative analysis of 6 different sake samples for SAOs with DP = 2-8 and the other saccharides showed that the amount of each SAO differs significantly among the sake samples. Enzymatic digestion analysis suggested that the SAOs are probably branched maltooligosaccharides in structure, which are resistant to beta-amylase. (C) 2017, The Society for Biotechnology, Japan. All rights reserved.