These results indicated that the death of yeast cells in sake mash followed by the leakage of the cellular contents increased the DMTS-pp of sake, which was further enhanced by incubation. To confirm this finding, we attempted to kill the yeast cells in sake mash by adding ethanol at a final concentration of 25%. The resulting sake mash was incubated for 2 days at 15°C to promote leakage of the cellular contents into the mash. The MB staining ratio of the sake mash after incubation for 2 days was 100%. Furthermore, the sake mash was centrifuged to obtain a supernatant, which was designated as ethanol-added sake. The increase in A260 values after the addition of ethanol indicated that the contents of yeast cells leaked into the sake ( Table 3). The DMTS-pp of sake samples increased after the addition of ethanol and further increased after incubation for an additional 7 days ( Table 3). When the ethanol-added sake was boiled, the DMTS-pp value increased on day 0, although it did not further increase after incubation. As mentioned above, these results suggested that the yeast cells contained both heat stable and heat unstable compounds that participated in DMTS formation.