Cold Brewing Coffee

Cold brewed coffee has been available for longer than I have been alive, yet I had not sampled it until last week.  My local roaster was offering for sale the Toddy Cold Brew System for home use.  When I asked him about the merits of the system he simply told me to try a cup at the downstairs cafe.  I always follow his advice and did this time as well.  I had the coffee cold and asked for no ice.  I received about ten ounces of the most delightful cold coffee I have ever enjoyed.  It was fruity, soft and very different than any I have had before.  Makes sense, as cold brewing lowers acidity and caffeine.  I was excited to try making it at home.

I visited the roaster again this week, brought the system home and fired it up.  Only without the fire.  The only heat was generated from my burr grinder, which was designed to grind a half ounce at a time for espresso.  I gave it a rest after each of twelve ounces was ground (the maker suggested twelve ounces of coffee, but said a full pound could be carefully brewed).  The grinding process was a pain and I worried I was shortening the life of the grinder.  

Next time I will have the roaster grind it for me (something I would never do if I meant to brew the coffee over a period of days, but here the whole quantity gets used at once so it seems to be the best approach).

I started the brewing process at 11:00 am.  In my haste, I didn’t consider the twelve hour suggested brewing time.  As it was, I should have let it brew until 11:00 pm, but I am happiest to start sleep at 10:00 or even 9:00 when allowed.  Considered setting the alarm for 11:00 pm, but then I would have wanted to babysit the thing for at least half an hour to make sure it drained and to put it in the fridge when it was done.  I value sleep even more than coffee, so I pulled the plug after ten hours.  

I was relived to see the concentrate draining from the brewing chamber at roughly the pace of espresso draining from an espresso maker.  At that pace, it shouldn’t take long to drain the expected 36 ounces, but I had my doubts.  Some users have reported draining problems.  The system has a polyester filter at the bottom of the brewing chamber which can become clogged if the coffee is ground too finely or if the coffee grounds are disturbed during the wetting process.  If the filter clogs, the user is advised to use a tool to reach through the grounds and scrape the top of the filter.  I pictured the clog recurring repeatedly during the draining process and the whole process becoming generally not fun.

Happily the pace of draining was more or less constant and then stopped after thirty minutes.  No fiddling with the filter.  Having been through one brewing cycle, it is obvious that I should buy the coffee in the afternoon, start the brewing in the evening and drain the system upon waking.

I ended up with 32 ounces of concentrate, rather than the 36 ounces.  Might not seem like much of a difference, but four ounces short means two fewer cups of coffee.  Let me explain.  Our coffee cups hold 6 ounces of coffee.  The system maker suggests diluting the concentrate by a ratio of three to one (that is, three parts water to one part concentrate).  When aiming for six ounces of finished coffee, I’d use 1.5 ounces of concentrate and 4.5 ounces of water.

That said, I preferred the coffee resulting from two parts water to one part concentrate.  Some users even reported preferring a one to one ratio.  I wonder if some new tasters, myself included, wanted stronger concentrations to try to bring back some of the acidity to which they are accustomed.  Time will tell.  My current preference for a stronger concentration might change when I brew for the entire twelve hours.  It also occurs to me that the ambient temperature probably makes a difference with cold brewing.  While hot brewing generally occurs in an 180 degree environment, the temperature of the mix during cold brewing is dependent on the ambient air temperature.  In our home, that can vary considerably.  Maybe cold brewing during the summer requires fewer than twelve hours and during the winter requires a longer cycle.

Lacey and I each had a hot cup this morning (mixed at two parts water to one part concentrate).  We arrived at a hot cup by adding concentrate to the cup and then adding hot water.  I have not done a blind taste test, but for now I will say the end result was not remarkably better than  hot coffee brewed in our french press.  I am guessing that adding hot water can change the flavor of the concentrate in some of the same ways that brewing with hot water would.  You should still have lower acidity and caffeine, but for now I will guess cold brewed coffee might best be enjoyed cold.

Then there is the cost.  Cold brewed coffee is the clear loser here.  Cold brewed coffee mixed at three to one costs $0.50 a cup (beans cost $14.50/pound).   Cold brewed coffee mixed at two to one costs $0.65 a cup.  Hot coffee brewed in the french press costs only $0.36 a cup.  Apples to oranges, but since I did the math, a double espresso costs $0.44 a cup.  Interesting that they are all in the same neighborhood (and so very much lower than the prices paid when others do the work for you), but having done the math and tasted the results, I will not be selling my french press.  I will probably use it for morning coffee and also have a pot of concentrate in the fridge in the summer for cold coffee drinks.  I will never give up my afternoon espresso.  To me, extraction in an espresso machine is by far the best way to enjoy well roasted beans.

I will not give up.  I will continue to fiddle with the cold brew system.  My roaster said they have enjoyed the results from finer ground beans.  This may work in the commercial maker, but it will be interesting to see if draining issues arise when I use finer grinds.  As always, it will be fun to experiment and to share.


10 responses to “Cold Brewing Coffee

  1. Indeed, two things stopped my cold brewing shortly after it started. One was the relatively high bean-to-beverage ratio… as you say, the suggested mix concentration was a little weak for me. The second factor was that the caffeine dose was tangibly MUCH higher, to the extent that I clearly would not be able to function in society when drinking it regularly.

    • Thanks for the note! I think I first heard of cold brewing from you, and when we had that conversation you mentioned the higher caffeine content that resulted. Having bought the system and reading a bit, I noticed the claims of lower caffeine which contradicted your statements. I am glad you wrote, so that we can discuss it more.

      I cannot measure caffeine, so I am relying on the statements from the manufacturer and assertions in this article (

      When the manufacturer and the reporter in the article arrive at lower caffeine contents from cold brewing, I am assuming they are measuring the caffeine in a mix of concentrate and water diluted 1 to 3 (the manufacturer’s recommended dilution). So many variables could affect caffeine content, but let’s start there.

      In the article, the manufacturer claims the finished drink should have as little as 33% of the caffeine of hot brewed coffee (C of HBC). Using this as a baseline, increasing the strength of the finished coffee by using one part concentrate to two parts water should result in 44% of the C of HBC. A one to one dilution would result in 66% of the C of HBC. The caffeine level of cold brewed coffee (C of CBC) doesn’t exceed the C of HBC until you consume it undiluted, at which point you’ be getting 132% of the C of HBC.

      The analysis cited in the article comparing cold brewed coffee to Starbucks found that the C of CBC was 66% of the C of HBC. Much more than the manufacturer’s stated floor for lowest caffeine, but still less than hot brewed coffee. Again, I will assume this result was achieved by measuring C of CBC after mixing one part concentrate and three parts water. With this as a baseline, increasing the strength of the finished coffee by using one part concentrate to two parts water should result in 89% of the C of HBC. A one to one dilution would result in 134% of the C of HBC. Undiluted concentrate would have a whopping 268% of the C of HBC.

      I think I prefer the results of mixing one part concentrate to two parts water. If I assume the manufacturer’s floor of 33% of the C of HBC, at our concentration I will be getting 44% of the C of HBC. If I assume the reporter’s result of 66% of the C of HBC, at our concentration I will be getting 89% of the C of HBC. Either way, the cold brewed coffee delivers less caffeine than I was getting using hot brewed methods (with so many imbedded assumptions as to make these assertions meaningless).

      The big question, then, is were you drinking straight concentrate? Little chance of that as I respect your palette (concentrate is foul) and your research abilities (hard to believe you hacked your way into the production of concentrate without reading that you are supposed to dilute the result). With that off the table, maybe you were simply observing your behavior having consumed concentrate diluted to your preferred taste. On that measure, I might agree that the caffeine content of cold brewed coffee, even after dilution, could be much higher than that in hot brewed coffee. Proof? I read your comment before a cup of cold brewed coffee and was going to simply reply with a request to you to show me some meth (I mean math). With a cup of cold brewed coffee in me, I was surfing all over the net, got out a calculator and a yellow pad and spent an hour composing this tome of a reply! Yikers!

      Luckily I work from home. I will let this buzz subside before I head out into the world (or reply to work email). If you should be willing to put samples of my variously brewed beverages in a super collider (or maybe even the right machine for measuring caffeine) at your work, I would be glad to provide whatever you require.

      Thanks again for your comments!

  2. This was fascinating! I’m always interested in coffee stuff, even though one sip of it makes me a crazy lady. I’ve always heard the cold brew was so amazing. Hmm…

    • Nice to hear from you! Based on two samples (the cafe’s and my one batch), I think cold brewed coffee can be amazing. The cafe’s was. Mine was less so. My main gripe is cost. I am fully on-board with your prescription for increased spending in the food department, but I want to see a return. Until I can make cold brewed coffee taste twice as good as hot brewed coffee, I will be bummed about spending twice as much.

      My friend in Portland (who comments via email) said he has moved to cold brewing and loves it. I didn’t get the sense that he finds it to be way better, but he does enjoy it and pointed out that brewing once a week is easier than every day. I do hate cleaning a french press. I have as much respect for his coffee advice as I do for yours in the vegan cooking and baking realms, which is to say an immeasurable amount, so I will give cold brewing a fair shake before I move the tools to the back of the closet.

      Thanks for writing. Good luck with the upcoming busy times. Hope to see you soon.

  3. Ah, good to read as I drank my morning espresso…was secretly hoping one of my friends would try out some of the cold brew methods and then report back to me. Finally mastered the espresso machine en mi casa. Will have to have you over for a pull!

    • Thanks for writing. Glad you have the espresso machine dialed in. Now the humidity, your beans, your grind, your tamp and a hundred other things will change so that you can master it again every day for the rest of your life!

      I am enjoying the cold brewed coffee here more each day. I am on my second batch. This time I saved by burr grinder and instead ground the beans in a basic blade grinder. I only needed to load the thing 6 times to get the 12 ounces, and ran it each time for nine seconds. It went much quicker and the uneven grind didn’t seem to cause any problems with flavor or draining. The convenience of not having to grind brew and clean up every day is a big plus, so maybe I get over the increased cost. My stomach thinks the decrease in acid is nice, too. If you want to try it but aren’t interested in buying the kit, it should be easy to hack your way into a batch.

      Take care!

  4. I cold brew all summer and I love it.
    I bought one of those felt-esque looking coffee sock things and I only have to filter it once and there’s no sediment. The Gimme! Coffee’s filter all their cold brews twice, once with cloth and once with felt. They use 5LBs of coffee to 4 gallons of water, then dilute it to taste depending on the roast. Tinker accordingly!

    Also, Randy, I’ve got some Gimme! Coffee beans and some new Direct Trade Mocha Joe’s that we should test out in your espresso maker some time soon!

  5. I never even considered diluting the concentrate.

    I used to make espresso, then, use that, but, now, w/ cold-brewing, I have a way to produce the greater overall taste + buzz I want; I only mix whatever coffee (concentrate or otherwise) to make a very sweet (to most people’s taste) mocha – and make it cold.

    The concentrate tastes great, esp. in my alchemy.

    I think your numbers may be right about the caffeine content; I think it may be more than just coffee, alone.

    • Thanks for writing! Using the concentrate to make a mocha is diluting the concentrate, assuming you make a mocha with milk of some sort. You are simply diluting the concentrate with milk rather than water. Or are you saying you can drink the concentrate straight, like an espresso? I’d guess not, as my concentrate is pretty close to undrinkable before dilution.

      I have made a couple more batches since writing this piece and have found that ratios as high as one to one make very wonderful coffee. Even so, at one to one the cost per cup is too high for my comfort. I’d rather just save the cold brew for the summer and mochas (as has been your habit).

      Thanks again for stopping by and dropping a note. Take care.

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