In our “Truth About Bitterness” series, we have explored the many and varied factors causing unpleasant bitterness in a cup of coffee. We hope we have helped you to identify coffees with “good” bitter flavours, which of course need to be in perfect balance with sweetness and acidity. All of the causes of “bad” bitterness we have identified so far, such as coffee defects and low acidity are traced to the supply side. They all have something to do with the quality of the coffee itself or the roasting process. In contrast, the final “truth” about bitterness starts in your own kitchen…
A dirty coffee machine is one of the most common culprits; it can impart bitterness to a cup of coffee made from even the very best of beans. We can't blame this problem on the beans or the roaster, but only ourselves! Luckily, it's a very easy to solve the problem of a dirty machine and redeem your barista-at-home credentials.
WHY DIRTY MACHINES MAKE BITTER COFFEE
All coffee machines, including modern capsule machines, get dirty with use. You can wipe down the outside and wash all the removable parts as often as you like, but inside the machine are various unreachable parts. With regular use, these inner parts of a machine collect and become coated with coffee residue and coffee oils that build up and become increasingly rancid. These rancid oils impart nasty, bitter flavours into every cup of coffee you brew.
HOW TO CLEAN A CAPSULE MACHINE
Cleaning all the removable and outer parts of a coffee machine simply requires hot, soapy water and a sponge. To tackle the inner parts of a machine, consult the instruction manual or manufacturer’s website.
REMOVE RESIDUE TOO!
In addition to regular cleaning and maintenance of your coffee machine, we have an additional tip for keeping bitterness out of your cup: Remove the residue left behind by the previous brew every single time you make coffee.
Every cup of coffee you brew leaves behind traces of coffee oils that quickly become rancid. Without flushing or washing away the residue, you can impart slight but noticeable bitter notes into an otherwise delicious cup of coffee. Simply run a shot of plain water – with no capsule in place – through the machine before brewing a pod. Doing this every time keeps all traces of bitter, rancid coffee oils out of your cup!