What Lies Beneath… Your Coffee Machine

New study reveals leftover coffee caught in drip tray promotes bacterial growth

You should probably get around to cleaning that drip tray.

At-home coffee brewers might want to take extra care in cleaning their machines, according to findings from a recent study published in Scientific Reports.

The study found that leftover coffee caught in the drip tray makes for a great breeding ground for certain types of bacteria. Specifically, in studying nine Nespresso machines that have been used for at least one year, between 35 and 67 different types of bacteria were found in the drip trays.

This discovery was surprising to the researchers, as the caffeine in coffee is a natural alkaloid with well-known antibacterial properties. The bacteria found on the machines were not only thriving but breaking down the caffeine without leaving behind a chemical residue.

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These findings are important not only for at-home brewers; caffeine is a big polluter for groundwater and the results of this study can be used to determine whether wastewater has been properly treated. Pinpointing the types of bacteria that thrive in caffeine and break it down will lead to easier decaffeination and newer and better treatments for polluted groundwater.