1. Extraction temperature matters

Hot brew (regular coffee): When you brew with hot water (90–96°C), you extract a wide range of compounds quickly — acids, oils, caffeine, sugars, and tannin-like compounds. This is what gives hot coffee its brightness, bitterness, and complex aroma.

Cold brew: With cold water (4–20°C), extraction is much slower and selective. Acids and bitter compounds dissolve far less, while sugars and caffeine still extract over time. That’s why cold brew tastes smoother, sweeter, and less acidic, even if it’s strong.

2. Chemical profile

Hot brew cooled down: If you take a normal pot of coffee and let it cool, you still have all the acids and bitter compounds that hot water pulled out. As it cools, oxidation kicks in, making it taste harsh, sour, and “stale.”

Cold brew: Because it never got hot, many of those sharp acids and bitter elements were never extracted in the first place. And since it’s brewed without heat, it oxidizes more slowly, staying smooth and stable for days.

3. Mouthfeel and use

Hot-brew-then-cooled = sharper, often unpleasantly sour and bitter.

Cold brew = rounder, chocolatey, low-acid, often described as “silky.” It also works great as a concentrate, for mixing with milk or as iced coffee.

So the short answer: Cold brew and cooled-down coffee are chemically and sensorially different drinks. One is smooth and sweet because cold water never pulled out the harsher stuff. The other is just regular coffee that’s lost its heat — and often its charm.