Moreover, the preliminary bitter/bitterless classification model in the work of Wiener et al., which is trained on the dataset including the non-bitter flavors and 2,000 diverse molecules selected from ChEMBL database (Gaulton et al., 2012) as the hypothetical non-bitterants, is probably not very promising, since there is no detailed performance evaluation about this preliminary model mentioned in their work, and actually these 2,000 compounds from ChEMBL database are excluded in the model-training to achieve their final best classification model (Dagan-Wiener et al., 2017). Therefore, our work does not take account of the hypothetical non-bitterants in our dataset.