3 reasons Why your coffee tastes bitter and burnt, and how to fix it

Coffee is bitter and there is no getting around it and will always be present in some concentration in your cup of coffee. There are many flavour compounds in coffee that give rise to bitterness, with the main culprit being our very good friend, caffeine. However, if you believe your brew is excessively bitter, there are a number of reasons why this could be.

Dark roasted coffee

If your coffee is darkly roasted and glistening with oil on the surface of the bean, this is likely why your coffee is tasting excessively bitter and burnt. Over-roasting coffee beans essentially turn the cellulose fibres into carbon – the same thing as the char on your food when barbequing.

dark roasted coffee
Above: darkly roasted coffee with a sheen of oil on the surface

To make darkly roasted coffee taste better, you’ll want to limit the level of extraction (how much flavour your pull out from the coffee), potentially under-extracting the coffee on purpose.

There are a number of ways to limit the level of extraction including:

  • Reducing the amount of water used to brew the coffee. For espresso, you’ll want to be in ristretto territory. For filter coffees, you’ll want to use around 14g of water to every gram of ground coffee
  • Reduce water temperature. For espresso, this may not be easily achieved. If you have a PID, you can easily set the machine for a lower brew temp, aim for 85 to 88 degrees Celsius. If your espresso machine is a heat-exchanger, you’ll need to adjust the pressure-stat so the boiler around 0.7 bar. For filter coffee, allow the kettle to come off the boil and let it sit for 3 minutes before using it. If you have a modern electronic temperature adjustable kettle, set it for 80-85 degrees Celsius.
  • Grind your coffee coarser. This will limit the amount of surface area accessible to the water for extraction.
  • Brew faster – the less time the coffee is in contact with the water for, the less flavour you can draw out. For percolation methods like espresso and paper filtered coffees, this will tie in with the previous point, as a coarser grind setting will cause a shot/draw-down time. For immersion methods like plunger/French press, set a timer for 2 minutes and end the brew.

Dirty coffee equipment

When was the last time you cleaned your coffee equipment with specially formulated coffee cleaning detergents?

For espresso machines in a commercial setting, we recommend you backflush with detergent daily after service. For home baristas, every fortnight (two-weeks) should be sufficient to keep your espresso tasting clean and vibrant.

If you own a batch brewing/auto-drip style machine, we recommend the same cleaning schedule as above for espresso machines. Clean everything that comes into contact with brewed coffee until they’re sparkly clean such as the basket and carafe.

Clean your coffee grinder

Regular maintenance of your coffee grinder will keep your coffee drinking experience as tasty as possible. If you feel comfortable doing so, disassembling your grinder and cleaning the burrs and grinding chamber of stale ground coffee will ensure your coffee tastes as good as it should.

For cafes, this should be done on a weekly basis to ensure there is no major oil and superfine coffee build up in the grinding path and on the burrs. At home, every 3 months should do. Your cleaning regime will obviously depend on the volume of coffee you are grinding.

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