Why does my pour-over coffee taste sour?

The perception of sourness in coffee is a diagnostic signal that the brewing process was halted prematurely. Coffee extraction is a sequential process: organic acids and fruity compounds are the most soluble and dissolve first, followed by sugars and, finally, heavier, bitter-tasting compounds. When a cup tastes sour, you have successfully extracted the acids but failed to reach the 'sweet spot' where sugars dissolve to provide balance. A common misconception is that the coffee beans themselves are 'too acidic' or defective. In reality, even high-scoring specialty coffees—often prized for their bright, vibrant acidity—will taste thin, hollow, and aggressively sour if the extraction yield is too low. From a producer's perspective, this is a tragedy of preparation; the complex enzymatic and sugar-browning flavors developed during the drying and roasting phases are left trapped inside the cellular structure of the grounds. To correct this, focus on increasing the extraction efficiency. A finer grind increases the surface area available to the water, while higher water temperatures (ideally between 90°C and 96°C) provide the thermal energy required to dissolve complex carbohydrates. If your technique remains consistent, these adjustments will shift the balance from a sharp, one-dimensional acidity to a nuanced, sweet, and fully developed cup.