I only use it to make dough. But at the bottom of the bread pan, some oily and black substance comtaminated the dough. I think it should be poisonous. and I throw away the dough. Does anyone has the same poblem? How do I prevent it? Another problem is I can't remove the kneading blade out to wash even I follow the manu to place warm water in the bread pan for 15 minutes. Thanks.