Cooling coffee rapidly without dilution

Question

I like iced coffee when the weather is hot, and I like to drink it black (or nearly black) and undiluted. What is a good setup for cooling freshly brewed coffee quickly, without a lot of hassle? I'm talking about normal brewed coffee, not cold brew.

At Starbucks, they seem to put ice in your cup and then pour coffee directly over the ice. This works, but it uses a lot of ice, and by the time you're done drinking it, the melting ice has started to dilute the coffee. You also just can't fit very much coffee in a cup this way, because so much space is taken up by the ice.

I've tried putting a whole bunch of water in a big pan, then sticking a thin-walled metal cup in the water and pouring the coffee into the cup to cool. This cools the coffee rapidly at first, but then the cooling process gets extremely slow. I think part of the problem is that the conduction and convection processes are slow, and also that the water's heat capacity isn't super huge, compared to the heat of melting of ice.

I homebrew beer, and to cool my wort, I have a coil of copper tubing that I insert into the pot and run water through from a garden hose. This is pretty efficient, but works for a quantity orders of magnitude greater than a cup of coffee. It uses a huge amount of water.

Below is a method that I'm currently messing around with. The pan of water is to take the initial heat off of the coffee and make sure the coffee is cool enough so that I don't melt a hole through the plastic parts or release bad chemicals into the coffee from the plastic. I then put some ice in the ziplock bag and stick it in. After a few minutes I can take the cup out of the pan. The ice melts, and then I replace it with fresh ice. This setup seems not too bad, but still kind of slow and wasteful. It uses up a lot of ice. I can wash and reuse the bag.

Is there a better way to do this? I'm fantasizing about weird gadgets such as an aquarium pump sending pre-chilled vodka or ice water through a closed loop of tubing. Or maybe putting pieces of brass or copper in the freezer.

Answer 1

If done right, you can use a combination of ice and hot beverage that will ensure that the ice cubes have melted almost completely once you have reached an equilibrium, i.e. a cold drink.

For my go-to ice tea, I use one full tray of ice cubes in my jug and pour the freshly brewed tea plus some sugar syrup and lemon right over it. In ratios, I need two parts of ice per three parts hot tea (by weigh) and end up with small ice cubes floating around. A little less ice would still give me a cool drink, but not ice cold, so depending on your preference, work from there.

This ratio also helps when calculating increased coffee strength - use 60-70% more coffee in your brew if your plan to dilute by pouring over ice. If you are using coffee ice cubes (hint: great way to not throw away leftover coffee), use your preferred ratio.

Time to do it:
Under seven minutes fror my iced tea (boil water, brew tea, add ice, simple syrup and lemon to the jug while the tea is steeping, pour tea over the ice, stir vigorously until the ice is melted, done), under two for iced coffee with my espresso machine (heat up machine, grind coffee, tamp, lock portafilter, add a cube or two of ice to cup, draw a double shot, done).

The difference to freezing coffee ice cubes is that it requires preparation (and they do get stale after a while) while I always have generic plain ice cubes in the freezer. I will however admit that coffee ice cubes in cold milk also makes for a nice summer drink.

Answer 2

Make ice cubes out of coffee.

Depending on how you brew your coffee, you might even have some surplus coffee from time to time. Just pour it into an ice cube tray.

Then put the coffee ice cubes into your freshly brewed coffee, as usual.

Answer 3

I'm a scientist not a cook, but this is how I would do it.

Conductive cup for the coffee. A thin-walled aluminium is best, but steel works reasonably ok. Glass or porcelain just insulates too well. (consider an empty cola can, that's about as thin-walled as aluminium containers get)
Put it in a container with crushed ice.
Add salt to the ice.

The crushed ice promptly becomes an ice slushy with liquid water at temperatures down to -20C, and with all the thermal benefits of ice's latent heat of fusion (the heat it wants to absorb when melting)

It should cool one cup of boiling water(coffee) down to about 2C in under 30 seconds,
and about 2 minutes later you have a solid block of iced coffee.

At least it does that for a lab specimen that needs to be cooled urgently.

Answer 4

Have you considered whiskey stones?

They are ice cold stones used in whiskey for the same purpose (to cool and drink whiskey without diluting the whiskey). You keep them in the freezer and use them exactly like ice.

Answer 5

You can get ice cubes covered in heat resistant, food grade plastic. I think they are called “plastic ice cubes”.

Answer 6

Use a metal (drink) shaker

I like ice coffee myself, and use the following near-rapid approach, which requires ice but without (too much; dependent on step 2) dilution:

1. Brew the coffee
2. Let it cool/cool it (see below) down to luke warm-ish
3. Add ice to a metal shaker and instantly pour over the luke-warm coffee
4. High tempo shake
5. Pour out the cold coffee without the ice

For me step 2 is quite simple as I make strong moka brew mixed wih a quite a lot of oat milk at fridge-temperature, but I guess a large glass (wide cross section) or a bowl could be a good intermediate stop for your warm coffee to reach luke-warm. You could also keep your metal shaker (the large part) in your freezer, and use it as the luke-warm mechanism before going into the shake-with-ice stage:

• 2.a. Bring out the shaker from freezer
• 2.b. Pour the warm coffee into the cold shaker
• 2.c. Clean your brewing accessories while the shaker itself warms up whilst the coffee in it cools down. Be careful that the shaker may become very warm, though, depending on how much coffee you are making
• 2.d. Pour the luke-warm coffee to another container (e.g. serving glass) and wash the shaker with some cold water just so it’s not warm when you add the ice to it
• 3 to 5: As above.

The key here is that a metal shaker is a great conduction of heat, and we are using the this property of the metal shaker in several of the steps above (quickly cool shaker in freezer > cool hot coffee in shaker > quickly re-cool shaker with cold water > mix ice into the conductive environment of the shaker > cool luke-warm coffee into cold coffee).

Answer 7

You wrote in your question:

At Starbucks, they seem to put ice in your cup and then pour hot coffee directly over the ice. This works, but it uses a lot of ice, and by the time you're done drinking it, the melting ice has started to dilute the coffee. You also just can't fit very much coffee in a cup this way, because so much space is taken up by the ice.

jmk responded in a comment:

If you don‘t like the dilution make the Coffee you want to cool twice as strong.

You responded in a comment:

Re the idea of doubling the strength of the brew, I think the main problem with this is that the dilution gradually increases while you're trying to drink your coffee.

Here's my suggestion: brew coffee twice as strong, and chill it with plenty of ice. After the coffee and the ice have mingled for about 30 seconds or so, strain the ice out and discard it.

By my calculations, if you mix coffee at 80 °C (176 °F) with an equal amount of ice at 0 °C (32 °F, freezing), the result will be diluted coffee at 0 °C (which is, of course, as cold as liquid coffee can get). The chilling will happen very rapidly, especially if you stir the mixture. Any excess ice will just remain as ice. If you then strain the ice out, this will obviously prevent the ice from diluting the coffee any more.

If you want to avoid diluting the coffee at all, put the coffee in a thin-walled metal cup and put the cup in an ice water bath. Make sure there's enough water to conduct the heat rapidly, and enough ice to keep the water bath ice-cold.

Yeah, both of these methods will consume a lot of ice. But you can make ice fast enough to chill all the coffee you want, can't you? If you can't, then the problem isn't the usage of ice; it's the capacity of your freezer.

Answer 8

What I have found most effective for this purpose is to keep a 0.5l water bottle in the freezer. Then I pour the coffee in a bowl, and put the frozen water bottle (with the cap closed) inside the hot coffee.

This way the coffee is cooled down quickly, without any dilution.

Obviously you should be careful that the outside of the water bottle is very clean before using it, anything stuck on the outside with end up in your coffee.

Answer 9

You seem to have gotten pretty close as you stated in your question

I've tried putting a whole bunch of water in a big pan, then sticking a thin-walled metal cup in the water and pouring the coffee into the cup to cool. This cools the coffee rapidly at first, but then the cooling process gets extremely slow. I think part of the problem is that the conduction and convection processes are slow, and also that the water's heat capacity isn't super huge, compared to the heat of melting of ice.

You could easily improve on that by changing a few things:

• add ice and salt to the water in your big pan. The ice obviously drops the water temperature, but adding salt will make it drop even further through freezing point depression:
  • −20 °C can be achieved with a 1:3 mass ratio of sodium chloride (table salt) to ice.
• add the coffee to the thin walled metal cup, and stir it. The coffee in contact with the cup walls cool down faster, so stirring moves the warm coffee closer to the cold metal walls.
• additionally, move the cup around or stir the ice+salt+water (best if not with the same spoon you're stirring your coffee! maybe just move the cup...) to ensure the coldest water is in contact with your cup.

These tips should help you speed up the cooling process without adding much cost.

Answer 10

There are products specifically designed for this purpose. For example, I owned for sometime the following iced coffee maker. It has a large thermal reservoir that is kept in the freezer ready for use, so that the hot coffee is chilled as it is poured into the flask.

Answer 11

The same way many people cool their tea - with a saucer!

Pour some of the coffee into a saucer (or lift some with a spoon) and then drizzle it back into the cup from a height of 1-2 inches (a taller mug can help prevent splashing.) You could also use a second mug in a pinch.

The coffee will break into droplets as it falls, vastly increasing the surface area in contact with air, and rapidly bringing the droplets very close to room temperature. Those droplets then cool the bulk of the coffee when they mix back in. Repeat until you reach your desired temperature.

This is sometimes called "saucering" and I learned about it from this answer over on the Physics StackExchange. Another answer on that question features quantitative measurement showing its effectiveness (the variant with a spoon, at least.)

In my own experience, I use this method to get fine adjustment to my tea temperature. I've found my tool of choice (the tea infuser) cools my large 14oz mug of tea about 1-2C each time I raise it and let tea drip from the bottom. Since I can perform this action about once per second, it's a very effective way to cool the tea quickly, especially since I can do it absentmindledly while doing other tasks.

Answer 12

Try to make a bigger batch, freeze it, then thaw when needed.

No idea if this will affect the taste, but with proper packaging (like maybe freezer bags with all the air removed) I can't see a reason why it should. Certainly worth a taste test at least.

Big advantage is that heat is WAY easier to produce than cold. Thaw it in a pot or a microwave, and stop just before it has completely molten. Voila, 0°C coffee in five minutes.

Answer 13

Here's a wacky approach -- get a commercial freezer plate like they use to make Turkish ice cream. Do whatever you do to quickly cool the hot coffee to room temp, and then drizzle it onto the freezer plate and scrape it into a mug. You can include sugar, honey, milk, etc to make ice cream, too. It's expensive and silly, but you'd be a hit at kids' parties and craft fairs.

Answer 14

Another scientist here — you could buy one of these Cool Down Drink glasses. This is the commercial version of the DIY salt-water eutectic mentioned above.

In between the walls of the glass is a material (I'm guessing salt-water mix, but it might be something else) that takes a lot of energy to melt, and has a freezing point of -4 degrees. Just keep it in the freezer, then take it out and pour your coffee in, rinse, refreeze, etc.

The company show some cooling curves here too.

Answer 15

Could you try to use dry ice? The CO2 would sublimate and leave the coffee undiluted.

Answer 16

I use pots and pans to cool hot coffee. You need two of them. Pour the hot coffee into one, put the other under cold water from the tap. Wait a min or two until the pot with the coffee warms up. Then pour out the cold water from the sink pot, and dump the coffee into it. Put the warm pot under the cold tap. Repeat until it's cool, usually takes 3-5 swaps. This gets it to cold-tap temp in minutes, at which point ice doesn't water it down too bad.

You can rinse the last pot and put it back on the rack/cupboard; coffee is water-soluble and so it doesn't need washing. You can also throw in a handful of spoons or forks to increase thermal capacity and heat transfer surface area. I often add all our spoons to the pot while its brewing; they come out hot, which means the coffee is colder before I even start my pan games.

Answer 17

You could filter the coffee over frozen ball bearings. A little experimentation with the size and depth of the bearings would be in order. Pour the coffee over the top, let it drain through a screen at the bottom (a small mesh food strainer would probably be enough. No dilution, clean-up is easy and it would essentially be ready at any time. Just keep a supply of bearings in the freezer.

Answer 18

As a fellow homebrewer, I too use a copper immersion chiller to cool my wort.

The problem with immersion chillers is the same as with ice baths (which is also a common homebrewing technique). The cold water immediately next to the vessel quickly absorbs the heat and then stops cooling. You need something to circulate the water. I swirl my immersion chiller around in my boil pot, but that's awkward and still takes a long time. You also mentioned that the immersion chiller uses a huge amount of water. I have the same issue with mine.

I suggest trying a counterflow chiller instead, which uses a tube within a tube. The drink flows one way through the inside tube and the cold water flows the other way through the outside tube. This provides two major advantages:

1. More rapid cooling.
2. You get more homebrew gear! (that may be reason enough by itself)

Counterflow chillers can be purchased as a whole unit, but they're also pretty easy to make yourself. Search online for various designs.

Examples:

https://byo.com/project/build-a-counterflow-wort-chiller/

https://www.homebrewtalk.com/threads/diy-counterflow-wort-chiller-build.537126/

A copper tube inside a garden hose works pretty well. Use an aquarium pump to pump the beverage and hook a hose up for cool water. For extra powerful cooling and water savings, use a second aquarium pump and a cooler full of ice water to circulate the water.

Another similar and simpler option would be to pump the hot beverage through your immersion chiller and drop the immersion chiller in a cooler of ice water. An aquarium pump could recirculate the beverage through the chiller or you could use a gravity feed with two pots.

For a small scale test, you could make a mini immersion coil with some 1/4" copper tubing and gravity feed from a pot on the counter to a cooler full of ice water on a chair to a pot on the floor. No pumps required!

And I'm saying "aquarium pump" because you mentioned in the original post. Find a food grade pump from your local homebrew shop. Aquarium pumps from the hardware store won't be sanitary and may not be able to handle the heat.

And think of how your beer will benefit from more rapid cooling!

Answer 19

Lots of great ideas and fun things to try on the weekend, but if you want minimal hassle before work try a casserole pan filled with ice and water and an bread pan to pour the coffee in. From your picture, it appears that the coffee is significantly higher than the chilling medium. Using a wider pan means more surface area between the coffee and ice water.

I'll make coffee, pour it into the bread pan and add ice water around it, and by the time I'm ready to make breakfast the coffee is room temp or below. Certainly some dilution there but not enough that I've ever noticed. I have an ice maker so the extra ice isn't really a concern for me - I pour the melted ice and water into my kettle for tomorrow's brew.

Answer 20

2 options:

• Cold Brew: This is my preference as there is more caffeine, less acidity, and a preferable taste to me. Although this is a different brewing method and will create a different flavor profile.

• Technology: HyperChiller Long Lasting Beverage Chiller, For Alcohol, Juice, Coffee, Hc2

Answer 21

The coffee nerds (me included) have this figured out and is quite simple depending what kind of coffee you are making, since you never said what kind you are doing I am gonna explain the two more common ignoring cold brew since you already said is not an option.

For filter/immersion coffee you can just use ice but take in mind the water in the ice for your recipe, if you use 300ml of water use 150ml of ice and 150ml of water. Here is a video by James Hoffmann explaining it. Just remember that once it is chilled you can just add more ice and it won't dilute it much.

For espresso there are various ways but most dilute it but there are gadgets like this one that help with that but of course you need to make quite a lot of coffee, or you can use one of those cups with some kind of gel inside that you put on the freezer and cool your drinks without diluting.

Answer 22

I make a big pitcher of iced coffee on hot days. I add hazelnut creamer, so it's already cooled a bit after that, and I take some out for my first glass and cool that with plastic fake ice cubes (which I will swap out for frozen ones as the water in them melts). Then I put the pitcher in the fridge for later.

I wonder how well it would work to place a serving in the freezer for a short time until cooled enough for your taste.

Answer 23

The simplest way seem to be: pour your coffee into something with high thermal conductivity, and high thermal heat capacity, which you have pre-chilled to the target temperature.

An extreme example would be a 1 foot cube of stainless steel with a hole in it. A more practical example already exists:

Domestic ice-cream makers

These work on exactly this principle, you pre-chill a heavy base in the freezer and then add ice-cream ingredients. It has sufficient thermal capacity you do not need to return it to the freezer to make ice-cream, you just stir as it chills.

Put coffee in and Bob is your uncle.

Answer 24

My aunt had a genius idea, her whole family only likes drinking iced coffee in the mornings. They have a big, closed-off pitcher of cold coffee in fridge. They brew more coffee each morning and when everyone finishes their cup or 2 of iced coffee, they add the coffee from the new pot into the pitcher, refilling it, and place it back in the fridge. They had a family of 6 who all drank coffee (pretty big pitcher) and they never had a problem with running out of cold coffee to make nice iced coffee's with. No issue with dilution or settling either. Whenever they saw the pitcher less that half full, someone would just brew another pot in preparation to dump in.