Three reasons why your cup of coffee tastes bitter

Baristador B70 Espresso Crema

Bitterness can begin with brewing

Have you ever had a cup of coffee that tasted bitter?

Chances are that as long as you are buying quality coffee, the bitterness was ‘created’ by your coffee-making technique.

A lot of research has gone in to what is responsible for reports of bitterness among some coffee drinkers.

According to Thomas Hofmann, a professor of food chemistry and molecular sensory science at the Technical University of Munich, while many people blame caffeine for coffee’s bitterness it really only accounts for 15 percent of the experience.

His research has shown that there are two chemical compounds developed in coffee as a result of roasting that lead people to ascribe bitterness to this beverage but they are also the antioxidants; something that attracts people toward coffee.

A seperate review of research, carried out by McCamey, D. A.; Thorpe, T. M.; and McCarthy, J. P., Coffee Bitterness, in “Developments in Food Science”, found that Robusta beans had higher levels of these compounds than Arabica beans (Baristador coffees are all Arabica).

This latter review also pointed the finger at brewing techniques for amplifying these natural qualities in roasted coffee.

So, what am I doing that’s making my coffee bitter?

Coffee experts agree that the following three principles will cause coffee to taste bitter:

  • Over-extracting your coffee
  • Using water that is too hot
  • Using the wrong grind size

Over-extracting your coffee

This is a trap for young players and I blame all the big name brands in coffee machines.

Over-extraction is when you pass (or ‘espress’) too much water through your coffee grounds.

Basically, once you have extracted your shot of coffee, you should STOP allowing your coffee machine to pass more water through those spent beans.

Once a shot has been extracted, water that follows draws numerous bitter compounds from deep within the grounds, compounds we should NOT be drinking.

So if you are lulled into a false sense of security by your machine which allows you to dial up a long black, you are prescribing yourself a cup of bitterness.

To get a long lack or a longer dose of coffee fo a milk drink (latte, flat white, etc), simply let your machine deposit a shot of coffee into your cup and THEN add some hot water to achieve your desired length.

You will instatly notice a sweeter, milder, more rounded result.

Using water that is too hot

Just like over-extraction, water that is too hot reaches too deeply into our humble coffee grounds and leeches compounds we don’t want to leech.

This is why good cafes never serve scaldingly hot coffee.

It is also why better coffee machines give you control over water temperature.

If your machine wont allow you to dial between 92 and 96 degrees Celsius, you possibly need a new machine.

If you are plunging, allow the kettle to sit for a minute or two after boiling to allow the temperature to reduce before pouring over the coffee grounds.

Another form of over-extraction occurs when you scimp on the dose of coffee you put in your coffee device. This will become more temptiing as coffee prices rise later this year (2011).

However, short-changing your coffee device leads to your coffee extraction running thinner and more bitter much faster than expected. So always fill your coffee basket or use generous scoops when preparing plunger coffee to avoid self-sabotaging your coffee experience.

Using the wrong grind size

Baristador, like most other coffee houses, offers its blends in three different ‘grinds’:
Whole beans – You grind these yourself and must experiment for your optimal grind size to suit your coffee device
Espresso grind – This is a finer grind suitable for espresso machines and stovetop espresso makers (as a standby you can use this grind in a plunger)
Plunger grind – This is a coarse grind just perfect for plunging. You CANNOT substitute this grind for espresso because the water will pass through too quickly.

I hope these notes will help you give your coffee (Baristador or otherwise) a chance to display their unique flavour profiles without being tarred by some coffee-making missteps.

PS Cleaning your coffee equipment VERY regularly will also flush away bitter residues which build up quite quickly.

Yours in the spirit of espresso

Steve Davis


  1. Jonathan says

    Hey Steve. Thanks for the advice. This helped a lot but I still have some lingering questions that are related to my situation. I live in South America, in Ecuador. I’m an American expat and I don’t have plans of going back any time soon. In Ecuador, the coffee that I can buy in the supermarket doesn’t have classifications as to the size of the grind (except for espresso). So I don’t know the optimal grind for the press. I have a cheap little press that I recently bought and began experimenting with, but I still find that the coffee is coming out bitter. I’m not using boiling water, I keep the press clean and I’m using generous amounts of the coffee that I’ve purchased. Do you have any further advice for a beginner? It would be greatly appreciated. I don’t know if you know this, but here in South America, instant coffee drinking is rampant. I’m using the heated water from the water machine to brew the stuff that I bring from home. Please help! I need a better coffee experience!


    • Steve Davis says

      Hello Jonathon, thanks for commenting. When you say ‘press’, I assume you mean a ‘plunger’ or are you referring to one of those older espresso machines in which you ‘press’ down the lever to espress the coffee? If the former, then you will need to look for a plunger grind OR consider buying just the beans and grinding the coffee yourself, coarsely. If the latter, an espresso grind should suffice.
      Part of me wonders whether the blend itself might be at fault? Do you know other people using this blend who get good results? Or could you take some somewhere else to try on different apparatus?
      Finally, how sad that instant coffee is all the rage in a part of the world that is hailed as one of the blessed coffee-growing regions.

  2. says

    Hi Steve, thanks for your advice on causes of bitter coffee.I am Kenyan and a first year student at Kenyatta university ,taking a bachelor of science that is tourism management.I was revising for my end of semester exam then i found some help from your article.Thanks very much and continue with the same.

    • Steve Davis says

      Basil, thank you for your comment. I hope you have done well in your exam.

      I am honoured to hear from someone who lives in the ‘birthplace’ of coffee.

      There is an email heading your way to ask you a couple more questions, if I may.

      Thanks again, Steve


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