@Abetillo In the canon, I'm pretty sure he still can't taste anything at this point due to his loss of faith in humanity. He doesn't know what anything tastes like, but it isn't an issue since the food he makes is delicious anyways.
Besides, he properly treats the ingredients. The meat quality mostly resembles that of a frog? make the leg meat the focus. The origin of the meat is a swamp monster? wash it repeatedly and thoroughly to remove any muddy smell and taste. The origin of the meat was a poisonous monster? carefully remove the source of the poison without damaging it, and treat it with detoxifying ingredients just in case. The results aren't random, all aspects are taken into consideration.