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If you’ve ever taken a sip of home-brewed coffee and recoiled at a bitter or sour taste, you’re not alone. While high-quality beans and fancy equipment help, the real key to great coffee comes down to balance in extraction - how water pulls flavor from coffee grounds. When extraction is off, so is your brew. Here’s a quick breakdown of what causes bitter and sour coffee, and how to fix it.
Bitter coffee is a sign of over-extraction, meaning the water extracted too much from the grounds - especially the woody, astringent compounds that are extracted last.
What causes it?
| Cause | Effect on Flavor | Recommended Adjustment |
| Too fine grind | Slow water flow → over extraction | Use a coarser grind |
| Water too hot | Scorches grounds, releases bitterness | Brew at 195°F–205°F (90–96°C) |
| Brew time too long | Overdraws bitter compounds | Adjust to optimal time for your brewing method* |
| Too much coffee | Overpowers the water | Adjust dose and aim for a balanced brew ratio |
Did You Know?
In terms of TDS, bitter brews may creep above 1.45% - 1.50% for drip or pour-over, which can signal over-extraction if the cup tastes harsh.
Caffeine contributes to bitterness but makes up only about 1.2% of a coffee bean's weight. Over-extraction magnifies its impact disproportionately.
*Brew time: Aim for 4 minutes for a French press, 2 to 4 minutes for pour-over, and 5 to 12 minutes for drip depends on the brew capacity and coffee model.
Sour coffee is often due to under-extraction, where water doesn't spend enough time dissolving the coffee’s full range of flavor compounds. This leaves behind acidic or grassy notes that feel sharp and unbalanced.
What causes it?
| Cause | Effect on Flavor | Recommended Adjustment |
| Too coarse grind | Water passes too quickly → weak flavor | Use a finer grind |
| Water too cool | Doesn’t extract enough flavor | Use water between 195-205°F (90-96°C) |
| Short brew time | Not enough contact time | Increase brew time by 10-20 seconds |
| Too little coffee | Brew is too diluted | Use a brew ratio of 1:15 to 1:18 (Coffee to water by weight) |
Did You Know?
For those using a TDS meter, sour or weak-tasting brews often read below 1.15% TDS for filter coffee - indicating under-extraction.
Chlorogenic acids (CGAs) break down into quinic and caffeic acids during roasting. If not properly extracted, CGAs dominate, causing sour or astringent notes.
Even with proper technique, these external variables can lead to bitterness or sourness:
| Factor | Potential Issue | Solution |
| Water quality | Soft or low-mineral water = dull or sour taste | Use filtered waterwith balanced minerals |
| Bean quality | Stale or under-roasted beans | Use freshly roasted beans within 2 - 4 weeks and store properly |
| Dirty equipment | Old oils and residue affect taste | Regular maintenance makes a difference |
A great cup of coffee isn’t about chasing perfection - it’s about balance. When grind size, temperature, time, and ratio come together, you’ll get a cup that’s rich, clean and enjoyable. And if you enjoy experimenting, a TDS meter can help you track consistency, with a target range of around1.15 - 1.35%for most filter-style coffees.
But you don’t need fancy gear to make great coffee - just a little curiosity and willingness to tweak one variable at a time. Taste, adjust, and repeat. Enjoy your coffee the way it should: balanced, sweet, and worth savoring.
READ NEXT: Understanding TDS in Coffee Read More →
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