Warm water extracts different flavors from the beans than cold water does. Also, some of those flavors will evaporate away when the warm coffee cools down. (Look up volitile organic compounds if you're interested in the science)
this post was submitted on 19 Aug 2025
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Other comments have already gone into it, but it's a different extraction process leading to a different flavour profile. The biggest difference AFAIK is that there are many acids in coffee that are highly soluble in hot water, but much less so in cold water. Typically this makes cold brews less astringent and sour and more smooth and kind of mellow.
I hate when i ask a coffee shop if they have cold brew and they say, "we can make it iced for you."
Gtfo like thats the same
Absolute facepalm moment.
This is why my wife gets a stomach ache from brewed coffee, but will absolutely destroy a jug of cold brew.
- 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.
- 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.
- 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.
It also doesn't really help that there are things like "Japanese cold brew", where you do a hot pourover into ice. Allegedly, the fact that it gets immediately cooled by dripping into ice means that volatiles get cooled and remain in the coffee instead of evaporating away, but I dont know if I buy that it would be a noticeable difference vs. just adding ice after brewing is done.
Not sure where I found a recipe but it's amazing for cold brew coffee
Ingredients
8 ounces whole coffee beans
8 cups (2 quarts) water, preferably flitered
Instructions Grind the coffee beans into a coarse grind. Grind the coffee beans in a coffee grinder until they are coarsely ground. Depending on the capacity of the coffee grinder, you may need to grind the coffee in batches. The goal is a coarse grind about the size of demerara or raw sugar.
Combine the ground coffee and water in the jar. Pour the ground coffee into a 3-quart jar or pitcher. Add the water.
Stir to incorporate. Gently stir the coffee with the water until well-blended. The coffee will float to the top as it sits, but don’t stress about that — just make sure all of the coffee gets wet.
Steep the coffee overnight in the fridge. Cover and refrigerate the cold brew for at least 18 hours or up to 24 hours.
Strain the coffee concentrate. Line a fine-mesh strainer with cheesecloth and set it over a large measuring cup. Slowly pour the coffee concentrate through the strainer. Depending on the size of your strainer, you may need to strain the coffee in batches. Fight the temptation to squeeze or press the coffee grounds in the cheesecloth.
Transfer to the cold brew to a clean jar for longer-term storage. Once strained, transfer the coffee to clean, airtight jars for long-term storage. Cover and refrigerate for up to 2 weeks.
Make your iced coffee. To serve, fill a glass with 1 cup ice cubes. Pour 1/2 cup the cold brew over the ice, add 1/2 cup cold water, and stir to combine. Add sweet cream or half-and-half if desired and enjoy.RECIPE NOTESStorage: Undiluted cold brew will last for up to 2 weeks refrigerated; diluted cold brew will last 2 to 3 days refrigerated.
Following.
Technically there are differences, as other have pointed out. In practice it tastes like cold coffee anyway.
Hot coffee in a pot gets a weird flavour after half hour, and when your pour milk in it it gets a grey tinge to the normal brown colour. Maybe a food science person can explain what happens to coffee
cold brew does extract differently. but yes, it's also generally old even when fresh. the stronger i brew it the less stale it tastes to me, so I wind up with a very high brewing ratio of something like 6:1 or less. and i like to drink it neat :-)
As stated in other comments, it's different than an old pot. But, the reason I've stopped drinking cold brew is that the flavor DOES remind me of old coffee. I'm much happier with an iced Americano.