How Gross Is Your Coffee Maker?

Ignorance is bliss when it comes to brewing coffee at home. Most java junkies are only concerned with flavor and strength, utilizing their preferred coffee maker and gourmet beans to achieve the perfect cup. Taste is the number one concern among coffee drinkers, after all.

But there's more than just coffee lurking inside those mugs of home-brewed joe, and it's not milk or sugar: It's the residue from your coffee maker, and all the bacteria that comes along with it.

"Germs are present in every corner of our lives," says Donna Duberg, M.A., M.S., an assistant professor of clinical laboratory science at Saint Louis University. "Are there germs in our coffee makers? Yes. Will they make us sick? Maybe, if there are enough of them, and especially if we don't clean our pots often enough."

It's not just the coffee pots that accumulate these germs, either. "Bacteria forms a slick biofilm when grown in moist, dark places, and so do molds," says Duberg, pointing to the coffee maker's water reservoir and piping system as ideal areas for accumulation. "If there is obvious slimy stuff in the coffee maker … this is a good sign there is something growing."

"Coffee mugs are usually [the] worst," adds microbiologist Dr. Charles Gerba. "In our studies, half had fecal bacteria in them. People probably contaminate them when they wipe them out with sponges or cleaning cloths."

Some coffee drinkers, however, point to the fact that coffee itself contains antibacterial properties that neutralize these contaminants. But as Duberg states, "While coffee brewed from roasted beans does have some antibacterial action due to its acidity, there is research which shows that it is only about 50 percent effective in killing bacteria, such as Staphylococcus aureus and Streptococcus mutans, and molds." Duberg also adds that green (unroasted) coffee contains none of these antibacterial compounds.

Even if a certain machine features a built-in water filter, Duberg warns that it won't eliminate germs. "Filtering water through an activated charcoal filter system does not remove organisms — just chemicals and metals, such as lead, depending on the filter."

Running heated water through the machine isn't enough to clean out the bacteria, either. "Water heated in the coffee maker — even the percolator types — is not hot enough to kill most germs," says Duberg. Water needs to reach the boiling point, she explains, and it needs to continue boiling for a full minute in order to kill harmful contaminants.

That leaves only one option: cleaning the coffee maker. Duberg recommends washing the removable components with hot, soapy water and letting them air dry once a week (or more, depending on how often it gets used), or placing them in a dishwasher and running them through the hot/sanitizing cycle. "This will remove the stains, residual oils, and reduce the number of germs," she says.

Then, once a month, run a solution of one part vinegar to one part water through the machine. "Vinegar is five percent acetic acid and actually disinfects the coffee maker, killing almost 100 percent of bacteria and viruses and most of the fuzzy molds," Duberg says. Simply start a cycle with the solution, then stop it halfway through and let the coffee maker sit for an hour. "Turn the coffee maker back on and complete the cycle," instructs Duberg. Once you're done, repeat the process (using the same vinegar solution is fine). Finally, run two cycles of clean water through the machine to get the vinegar out before brewing coffee.

Duberg also recommends preventative measures, such as rinsing the coffee machine's basket to remove any wet coffee grounds as soon as possible, as they have a tendency to grow mold spores which can be very resistant antibacterial compounds.

And don't forget about cleaning drinking vessels — especially at the office. "People don't seem to clean out office coffee mugs very well," notes Dr. Gerba. For the cleanest results, bring drinkware home from work, place it in the dishwasher, and air it dry.

Not only will these sanitation routine yield a cleaner machine, they'll result in healthier coffee, Duberg stresses.

"The goal of cleaning is to keep these bugs down to the lowest level possible, so if they get inside us, our body's defenses can eliminate them before they multiply and make us sick," Duberg says.

To put it bluntly, cleaning the coffeemaker is a chore no one can afford to ignore. Besides, ignorance is only bliss until someone gets sick.