Why does my cold brew taste acidic?

Cold brew is celebrated for its smooth, low-acid profile, which is a result of the long, slow extraction process using cold water. Unlike hot brewing, which uses heat to rapidly pull out acids and oils, cold brewing relies on time to extract the deeper, sweeter compounds from the coffee. If your cold brew tastes sharp, sour, or unpleasantly acidic, it is a sign that the extraction process was incomplete.

The most common cause of under-extracted cold brew is a grind size that is too coarse. Because cold water is less efficient at extracting flavor than hot water, the coffee particles need to be exposed to the water for a long time. If the particles are too large, the water cannot penetrate them effectively, leaving the inner compounds locked away while only the surface acids are dissolved. Try adjusting your grinder to a slightly finer setting to increase the surface area.

Brewing time is the second major variable. If you are steeping your coffee for less than 12 to 16 hours, you may not be giving the water enough time to fully extract the sugars and oils that balance out the acidity. Experiment by extending your steep time by a few hours. Keep in mind that the ambient temperature of your kitchen can also affect the rate of extraction; if your home is cool, you may need to steep for longer than you would in a warmer environment.

Finally, consider the coffee beans themselves. Some origins, particularly those from East Africa, are naturally high in acidity and bright, fruity notes. While these are desirable in a pour-over, they can sometimes translate to a sharp, citrusy acidity in cold brew that some drinkers find off-putting. If you prefer a more traditional, chocolatey, and low-acid cold brew, look for beans from Brazil, Colombia, or Indonesia, which typically have a heavier body and lower natural acidity.

In practice, treat your cold brew like any other brewing method: adjust one variable at a time. Start by extending your steep time, and if that doesn't resolve the acidity, move to a slightly finer grind. By fine-tuning these parameters, you can achieve the rich, mellow, and refreshing cold brew you expect.