What does a great cup of coffee mean to you?
Chances are you’ll be thinking of words like “smooth”, “velvety” and “aromatic”. What you definitely don’t want is a cup of Joe that leaves you screwing up your face like you’ve sucked on a lemon.
So if you’ve ever asked yourself, “Why does my coffee taste bitter?” – don’t despair! We’ll take a tour of the causes and explain what you can do about them.
Read on, and be prepared to make bad coffee a thing of the past.
Bitter, sour or just nasty?
There are plenty of things that can get in the way of a great cup of coffee. If you’ve got hard water, it can leave a sediment in your cup.
Brewed coffee left in the open air can quickly go stale. Fail to extract the flavors from your beans properly and you’ll be stuck with a sour taste.
Bitterness, though, is something quite different. It’s the kind of flavor that makes you pull a face and put down your cup. And it’s the result of one specific flaw in the brewing process: over-extraction.
To understand what that means, let’s take a look at the basic chemistry of coffee making.
The right chemistry
About 28 per cent of the mass of a coffee bean will dissolve in water. The rest is cellulose and plant fibres. It’s the simple process of adding water that turns those beans into your favorite drink.
Different flavors are extracted from the coffee bean at different stages in the brewing process. And not all of those flavors are good. What you’re aiming for in the perfect brew is all the good flavors with none of the bad.
If you don’t take enough flavor from the bean, your coffee will be under-extracted. It will taste sour and perhaps even salty.
Over-extracted coffee, on the other hand, will release bitter-tasting compounds into the water. Horrid!
So how do you guard against over-extraction?
Get the temperature right
Brewing your coffee with the right temperature water is crucial to avoiding bitterness. The hotter the water is, the quicker it will break down the coffee bean. That means there’s an all-important relationship between water temperature and brewing time.
If the water is too hot it can scald the beans. It will also release the different compounds that affect flavor very quickly. That means it will be hard to avoid the bitter substances released later in the brewing process ending up in your cup.
The ideal temperature for coffee brewing is generally accepted to be just below boiling point. Aim for between 195 and 205 degrees Fahrenheit.
Of course, there is also the option of cold brew. Because this uses cold water to extract the flavors of the bean, the brewing time is much longer. You should aim for a minimum of 24 hours.
If you have the patience to wait, you’ll be rewarded with deliciously smooth coffee. You won’t have to worry about bitterness – and as an added bonus, it’s easier on sensitive tums.
Don’t leave it too long
Leaving hot coffee to brew for too long has much the same effect as water that’s too hot: a bitter taste.
The right brewing time will depend on a number of factors: brewing style, water temperature and grind size. The perfect extraction time in an espresso, for example, will be much shorter than for a drip coffee.
That’s because in espresso the water is passed through the grounds at very high pressure, extracting flavors more quickly. In drip coffee, the water needs to be in contact with the grounds for much longer.
There’s one easy way to avoid getting your brewing time wrong: use a tried and tested recipe. This YouTube recipe shows the importance of timing in making pour over coffee.
The daily grind
The size of your coffee grounds has an important part to play in getting the perfect flavors. The smaller the grounds, the faster the flavors will be extracted.
Different grind sizes suit different brewing styles. For a French press, you’ll need a coarser grind, whilst for Turkish coffee it needs to be very fine.
But whatever style you use, make sure the water isn’t in contact with the coffee for too long. If it is, the result will be bitter flavors.
This YouTube video shows the effect of grind size on extraction time. It also explains what the combination of those two factors means for the taste of an espresso.
The right mix
The ratio of water to coffee in your brew is also very important for flavor. Strictly speaking, it’s coffee strength that’s affected here. The more coffee you put in the same amount of water, the stronger it will be.
But that’s not the whole story. In a stronger brew, also you’ll have more caffeine – and caffeine can have a bitter flavor.
It’s also worth mentioning the coffee itself. Individual varietals will have different flavors, and different roast profiles will affect those too.
And then there are the two basic coffee types, Robusta and Arabica. Robusta beans have a more bitter flavor. Make a coffee with a high ratio of Robusta beans to water, and you’ll end up with a bitter drink.
It’s worth mentioning that this doesn’t have to be a bad thing. In Vietnamese coffee, the bitterness of local Robusta beans is balanced with condensed milk for delicious results.
The National Coffee Association recommends a “golden ratio” of one to two tablespoons of coffee grounds for every six ounces of water.
Ready to brew?
We hope you’ve enjoyed our overview of the different factors that can lead to bitter coffee. As we’ve seen, it’s important not to look at any one of these in isolation.
Water temperature, grind size, brewing style and extraction time all combine to produce the flavors in your cup.
Whether you prefer punchy espressos or creamy lattes, we hope we’ve helped you understand how to get great results. Here’s to the end of bitter coffee!
My name is Kathy Gallo, Editor of Daily Cupo, a Coffee buff. The guide you find here is designed exactly for you, and it is our hope that you find it not only interesting but also actionable.