Your coffee machine could be one of the dirtiest parts of your kitchen if not cleaned often. Bacteria, yeast, and mold could be growing in your machine because of irregular cleaning, and those little devils don’t discriminate — it doesn’t matter whether you have a coffee pot, a Keurig, or a fancy espresso machine.
… Researchers say the part of the machine that stores water is the biggest culprit of disgustingness: half of the coffee reservoirs tested contained mold and yeast. The intense heat from the machine will kill some of the bacteria, but it’s not saving you from all of it.