Unmasking Sour Coffee: Expert Tips and Fixes
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Unmasking Sour Coffee: Expert Tips and Fixes

Whether you’re a newcomer to the world of specialty coffee or a seasoned aficionado, you’ve likely encountered a sour-tasting coffee at a coffee shop or in your own kitchen. If you’ve ever wondered why your coffee tastes sour and how to fix it, you’ve come to the right page.

Sour coffee is an unfortunate experience that can leave you questioning everything. Is this what specialty coffee is supposed to taste like? Am I brewing it wrong? Did the barista mess up? or even worse.. am I supposed to enjoy the sourness? Recognising that sourness is not ideal and understanding why it happens is the first step to improving your specialty coffee experience.

Recognising Sour Coffee

To identify sour coffee, it’s essential to understand the basic taste categories: sweet, salty, sour, bitter, and umami. Sour coffee has a distinct sharpness that is immediately noticeable, often hitting the sides of your tongue and leaving an unpleasant aftertaste. This sharpness can create a puckering sensation in your mouth, similar to sucking on a lime. Unlike the balanced acidity that adds brightness and complexity to a good cup of coffee, sourness overwhelms the palate and detracts from the overall flavour experience. Recognising these characteristics is the first step.

Acidity vs. Sourness: Understanding the Difference

Acidity in coffee is often misunderstood. While sourness is an undesirable flavour, acidity is a positive attribute that adds vibrancy and complexity to your coffee. Think of acidity as the effervescence in a sparkling water; it brings life and excitement to the drink.

The Role of Acidity in Coffee

Different types of acids contribute unique notes to the coffee, which essentially aids in enhancing overall taste. Here are the main acids found in coffee:

  • Citric Acid: Found in lemons, limes, and oranges, citric acid imparts bright citrus notes to coffee.
  • Malic Acid: Present in green apples, this acid adds a crisp and tart quality.
  • Phosphoric Acid: Common in soft drinks, phosphoric acid gives a sweet and tangy flavour.
  • Acetic Acid: Similar to the sharpness of vinegar or sour beer, acetic acid can add a bite to the coffee.
  • Lactic Acid: Found in milk and yoghurt, lactic acid contributes a creamy and smooth acidity.
  • Tartaric Acid: Present in grapes and bananas, tartaric acid adds a fruity and wine-like character.

Different coffee-growing regions with their own unique terroirs and growing altitudes produce coffee with varying levels of acidity. For instance, Brazilian coffee tends to have lower acidity, resulting in smooth, nutty flavours. In contrast, East African coffees, such as those from Kenya, are known for their high acidity and fruity, zingy profiles.

I know what you’re thinking.. What about that citric acid? Isn’t that what makes my coffee sour?
Great question! 

Citric acid similar to that found in lemons and oranges, adds a refreshing citrus note to coffee, contributing to its complexity and brightness. When balanced correctly, this acidity enhances the coffee’s flavour, making it vibrant and lively. However, if the coffee is subpar and/or not brewed with precision, the citric acid can become overwhelming, shifting from pleasant acidity to unpleasant sourness.

Think of citric acid in coffee like the lemon juice in a perfectly made guacamole. When used in the right amount, lemon juice brightens and enhances the flavours of the avocado, cilantro, and other ingredients. But if you add too much lemon juice or don’t balance it with the other ingredients, the guacamole becomes overly sour and loses its creamy, rich texture. Similarly, properly balanced citric acid brings out the best in coffee, while imbalance leads to an unpleasant experience.

Why Your Coffee Tastes Sour: Common Causes

  1. Under Extraction The extraction process dissolves acids, sugars, oils, and other flavour compounds from the coffee beans. If your coffee is under-extracted, it means the brewing process didn’t allow enough time for these compounds to dissolve, resulting in a sour taste dominated by unbalanced acids.
  2. Under Roasted Beans Roasting transforms green coffee beans into the flavourful brown beans we love through a complex chemical reaction known as the Maillard Reaction. If the beans are under-roasted, they don’t develop the necessary flavours, resulting in sour and earthy notes. Under-roasted coffee is exceptionally challenging to correct and balance. It often results in a sour and watery cup, or a bitter and astringent brew lacking complexity and texture, making it difficult to achieve anything pleasant.
  3. Stale Coffee Beans Over time, coffee beans degrade, losing their aromatic oils and breaking down the sugars and acids that contribute to a balanced flavour. Stale coffee often tastes sour and harsh, and this is much harder to fix. The beans have lost their essential qualities, resulting in a brew that’s flat and unappealing. So, ensure you use freshly roasted beans to avoid this issue.

Simple Solutions to Fix Sour Coffee

  1. Grind Finer Coarser coffee grounds take longer to extract, often leading to under-extraction. Grinding your coffee finer ensures a more complete extraction, balancing the flavours and reducing sourness.
  2. Increase Brew Time If adjusting the grind size isn’t an option, try increasing the brew time. Extending the brew time allows more flavour compounds to be extracted, leading to a more balanced cup.
  3. Adjust the Coffee-to-Water Ratio Tweaking the coffee-to-water ratio can make a significant difference. Increasing the amount of water used helps dilute overly concentrated sour notes, creating a more balanced brew.

Choose the Right Beans

Be cautious of light or lighter roasts that are often misrepresented as medium roasts, particularly from roasters who do not prioritise flavour development. These coffees can be challenging to balance, often resulting in a subpar brew.

It’s also advisable to use coffee within 2-4 weeks of the roast date for optimal freshness. Coffee beyond four months from the roast date can taste stale unless it has been adequately frozen.

Select coffee beans that align with your taste preferences. If you are sensitive to sour notes, opt for beans from regions like Brazil, Sumatra, or Central America, which tend to have lower acidity. Additionally, blends specifically roasted to reduce acidity can be a great choice.

At Specialty Batch, we offer a variety of coffees with detailed tasting notes to help you find the perfect match. Don’t hesitate to ask for recommendations based on your flavour preferences.

For more expert coffee insights and to explore our range of carefully curated beans, visit Specialty Batch today.

Considered as one of the region’s pioneers in specialty coffee education and Dubai cafe culture development, Ryan Godinho is an Australian entrepreneur who is accredited as the country's first SCAA AST and National Coffee Championships Coordinator. He is a frequent contributor to Forbes and Entrepreneur Magazines and also holds a postgraduate Certificate of Advanced Studies in Coffee Excellence from Zurich University (ZHAW).


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