- 第3日 6月24日（金） P会場（501，502，503）
A number of off-flavor events regarding tap water have occurred across Japan. Fishy smell is the second most common off-flavor in Japan. Its causative substance (hereafter referred to as FX) is still unrevealed to the best of our knowledge. The authors have found one of the causative substances and elucidated its structure partially, but not yet identified it. The number of the candidate structures of the FX was 14 at the moment. Therefore, the objective of this study is to narrow down the number of the candidate structures with a quantum chemical calculation method, the scaled hypersphere search/anharmonic downward distortion following method. A product ion that can be produced quantum-chemically from a specific moiety was successfully explored, indicating that the number of carbon chain of the FX’s alkyl ketone is six. The quasi-equilibrium theory was adopted tentatively to one of the remaining candidates. The number of the candidate structures of the FX was narrow down to five.