Bitterness is often seen as an unwanted quality in coffee, which is why some non-coffee drinkers avoid the beverage altogether. Others may associate bitterness with burnt or ashy notes. However, bitterness is a key component of coffee's complex flavour profile. In fact, it’s an essential part of a balanced brew
Achieving a balanced extraction of flavour is what any skilled barista strives to do with every pour. A well-brewed coffee delivers a harmony of savoury, sour, sweet, and bitter. If your coffee is tasting too bitter, we’re here to help you identify why and how to control it.
Over-Extraction
A common cause of bitter-tasting coffee is over-extraction, which occurs when hot water stays in contact with coffee grounds for too long. This pulls out an excess of bitter compounds that overpower the other flavours, often leaving a dry aftertaste.
When we brew coffee, the extraction process pulls compounds in this order: oil, acid, sugar, and bitter. So we need to aim for the sweet spot just as we begin pulling the bitter compounds.
How to Fix It
Since bitter compounds are the last to be extracted from the coffee, you simply need to control how much you extract. To do this, you might reduce the extraction time or use a lower water temperature.
Grind Size. To reduce extraction time, try using a coarser grind. Larger coffee particles create more space for water to pass through, preventing over-extraction. If your grind is too fine, the particles will pack closely together, causing the water to stay in contact with the coffee for too long.
The ideal grind size will vary between brew methods. French Press coffee uses coarser grinds (see How to brew coffee with a French Press) while espresso uses finer but in any method there is a possibility of brewing with a grind size that is too fine, leading to the bitterness from over-extraction.
Water Temperature. Water temperature plays an important role in the extraction process. If the water is too hot, it can lead to over-extraction. Specialty coffee is rarely brewed with boiling water; most brewers recommend a temperature range of 90ºC–98ºC.
Some machines don’t allow you to change the water temperature, and that’s okay. If you use a brewer like a Moccamaster (see Best Coffee Ratio for a Moccamaster)—or if you can’t adjust your kettle’s temperature—focus on changing the grind size to fine-tune extraction.
Low-Quality Beans
Low-quality beans may be poorly grown, roasted, or stored. A good roaster will sample the best quality from a producer, as well as share as much information about the producer, allowing transparency for customers to make informed decisions when buying a bag of beans.
Poorly stored coffee will see it lose its flavour over time, and unfortunately the bitter compounds are ones that outlast all the other compounds. So you’re likely only going to extract bitterness from stale coffee.
How to Fix It
It’s simple. Don’t skimp on coffee beans. If you’re purchasing cheap and low-quality beans, maybe you should stick to the jar of dirt you mix with milk? Finding high-quality coffee not only rewards you with the full experience, but also helps support a community of farmers and artisans.
High-Quality Beans.
Make sure you’re investing in high-quality beans from dedicated speciality roasters. A great way to find a passionate coffee roaster is if they have won any roasting competitions like the Golden Bean Australasia Roasting Competition. Roasters who constantly seek improvement and feedback from the coffee community are the ones to look out for.
Storing Coffee Beans. Keep your beans in an airtight container away from direct sunlight. This prevents oils and gases from releasing from the beans that are needed to extract a beautiful harmony of flavour.
Water Quality
Did you know that the quality of your water can affect the taste of your coffee? Water with high mineral content can cause over-extraction, while water with too few minerals can lead to a flat or under-extracted cup. Poor water quality can also introduce off-flavours that intensify bitterness.
How to Fix It
Use filtered water to ensure you’re brewing with balanced water. In some coffee competitions, some competitors buy bottled water just to be sure they’re brewing with clean water.
Bitterness is a flavour found in every cup of coffee. Making sure it works in harmony with the other compounds is essential to brewing a delicious cup. By controlling variables like grind size, water temperature, and bean quality, you can achieve a balanced extraction, resulting in a smooth and full-flavoured cup of coffee.
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