Do you wash your coffee pot every morning, or rinse and reuse the next day? What about the inside of the machine? Do you occasionally run a pot of water or vinegar through? Whether you use a single-use coffee-maker or a traditional multicup machine, they can be difficult to clean, so the rinse-and-reuse method is common. Because coffee is acidic, it should prevent the growth of bacteria. Right?
Actually, there are bacteria that are not only resistant to the acidity of coffee, but they also use the caffeine as an energy source. Moreover, these bacteria are able to quickly repopulate the machine after rinsing alone, and bacteria continue to grow in number and diversity the longer the machine is in use. To avoid unwanted contamination of our beverages with harmful bacteria, be sure you clean your coffee machines, inside and out, frequently following the manufacturer’s instructions.
Source: Vilanova C, Iglesias A, Porcar M. The coffee-machine bacteriome: Biodiversity and colonization of the wasted coffee tray leach. Sci. Rep. 2015;5:1–7. DOI: 10.1038/srep17163.