Troubleshooting bitterness and sourness
How to diagnose and correct the most common off-flavors in filter coffee: bitterness and sourness.
- Coffee Basics Nerds
- 1 min read
Understanding the Problems
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Sourness (Under-Extraction):
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Cause: Not enough soluble compounds extracted.
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Symptoms: Sharp acidity, thin body, grassy or lemony notes.
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Common reasons:
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Grind too coarse → fast flow, short contact time.
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Water too cool (<90 °C / 195 °F).
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Brew time too short.
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Under-dosing coffee.
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Bitterness (Over-Extraction):
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Cause: Too many soluble compounds extracted, including bitter alkaloids and tannins.
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Symptoms: Harsh, drying finish, hollow sweetness, lingering bitterness.
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Common reasons:
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Grind too fine → slow flow, long contact time.
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Water too hot (>96 °C / 205 °F).
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Brew time too long.
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Over-dosing coffee.
Corrective Actions
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For Sourness:
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Grind finer to slow flow.
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Increase brew time slightly.
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Raise water temperature.
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Adjust brew ratio (more coffee).
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For Bitterness:
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Grind coarser to speed flow.
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Shorten contact time.
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Lower water temperature.
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Adjust brew ratio (less coffee).
Practical Tips
- Always adjust one variable at a time.
- Taste systematically to isolate the cause.
- Record parameters to avoid repeating mistakes.
Summary
Sourness usually signals under-extraction, while bitterness signals over-extraction. By carefully adjusting grind size, brew ratio, temperature, and time, brewers can move back into the sweet spot for balanced, flavorful cups.