Shocking Espresso

Some things inherently sound like bollox. That espresso can be “shocked” is one of those things. It sounded so much like bollox that I bleated out such via twitter a little while ago and was met with a certain amount of people who agreed, and a certain amount who didn’t.

My error was in assuming it was bollox before actually testing it properly. Because sometimes things that sound like bollox… aren’t.

So briefly here was my test, which I did three times.

19g coffee, reaching about 30g beverage weight and 19% extraction in about 30s.

Incidently, the coffee was Hasbean’s (excellent!!) Bolivian Finca Bolinda.

Each shot was split. On one side over 32g of ice, and on the other into an empty (but otherwise identical) glass.

After brew 68g of cold water was added to each glass, followed by 32g of ice into the shot brewed into the empty glass.

Both beverages were allowed to sit for 10 minutes to thermo-equilibrate before tasting.

Tasing was a combination of sipping from the glass and slurping off a cupping spoon.




27 thoughts on “Shocking Espresso

  1. Jesse says:

    Curious about dilution. Would like to know what you find out about pulling shot into milk versus over ice with milk added.

    • Is there a reason I would want to find out about that? I mean, the whole shocking thing was about brewing directly on ice having some mysterious effect…

  2. I call shenanigans on this test because it may be flawed. The idea is to mimic what happens in a cafe, when an order for an iced americano or cappuccino (or iced espresso) comes in. Not many cafes leave coffee to sit and cool down for 10 mins.

    Would suggest this instead.

    a) Slow cool down shots: brew into cold ceramic; pour into secondary, serving vessel. Set aside.

    b) Fast cool down shots: brew directly onto ice. Stir. If ice cubes completely melt, you haven’t added enough ice.

    c) Take slow cool down espresso, add once ice cube, stir till dissolved. Add more ice to more or less match volume of the fast cool down.

    Sample. Right away. When I brew espresso this way (or a cafe brews onto ice directly) I get definite and unpleasant metallic notes. I’ve been able to recognize it in Vancouver cafes for years now without even seeing the brew process – I can taste when they brew directly onto ice.

    • The idea is not to mimic what happens in a cafe, but rather to ascertain whether brewing espresso directly over ice results in an effect commonly referred to as “shocking”.

      I think my test as outlined is sufficient to establish that.

      • But the “don’t shock espresso” thing was born out of serving iced espresso, americanos, cappuccinos etc at cafes.

        Plus, I don’t know very many coffees that doesn’t change flavours as they cool (slowly); Coffees sometimes dramatically change (for worse many times, for better sometimes) on the cupping table over a 10-15 minute tasting session. Add in the dilution you’re doing, and again, I call shenanigans on this test. Who knows -perhaps you found a way to overcome the metallic shock – dilute and age the coffee brew a bit. 🙂

        But the “shock” taste comes from an intensely rapid cooling, followed by a rapid serving to the customer, followed by a rapid first sip (esp. on a hot day). Maybe I’m particularly sensitive to it, but I taste it very often when cafes do their iced brewing this way (even if I haven’t seen the brewing process), and years ago when I tried these tests myself, I was able to test it as well.

        Perhaps I was biased thinking, okay, look for a metallic taste. But I’d say the same to you, Mr. Bias against any kind of difference 😀 We need true double blind tasting, and more closely mimicing what happens in a cafe.

  3. @Mark (taking this out of inline reply as it’s going to be one word per line) – double blind – yes – fine, except if you are biased at there being no difference. In any case I was not biased. I was quite happy to be proved wrong and I’ve outlined a simple method which others can replicate and say if they find different.

    I don’t believe the time is an issue. I think it is more important that the drinks are tasted at the same temp – which we know influences the taste.

    • I still think, to be ultimately fair to what many folks have tasted in the cup, you should do the same (or similar) tests that people who claim to taste a difference have done. That was my main point 😀

  4. Also want to add that, if memory serves correctly, Chris Davidson (the guy who instilled this idea in me in the first place) said the shock happened primarily because of crema (all those concentrated oils) at 95Cish falling and impacting sub-zero ice cubes in great density (compared to brewed coffee with the lower concentration of oils per ml) that causes the metallic twang taste. His theory (again IIRC) was the rapid temperature change to the oils shocked their taste into something less pleasing.

    This was why the metallic shock wasn’t evident in brewed coffee, but was in espresso brewing, when both are done onto ice.

  5. Freeze 60ml of water, pour one shot over that and another into 60ml of water from the espresso hot tap. Allow them to both reach room temp again.
    Would this not be a more stable test? The espresso in your test was poured into cold water. I don’t feel the myth is ice specific, it is more to do with accelerated change in temp of espresso by pouring it over something cold.
    I do like the experiment you did, something I have been doubting and I would like to see the myth debunked.


    • Crema has a much lower density of oils because it is just a foam of the coffee underneath it. Per gram of liquid crema (if we removed the suspended material) you’d see the same amount of foam as you would in the brewed liquid because they are essentially the same thing.

  6. Ice shocks espresso. It’s not bollocks. It’s absolutely true.
    It’s also true that ice sometimes doesn’t shock espresso.
    It depends on the espresso. I think it has to do with the choice of coffees, and/or the roast, because I’ve definitely experienced both results, and it definitely had to do with the coffee in some way.

    My hypothesis has been that it might be that dry-processed coffees to blame. I never got around to testing it very much though, which brings us to only one possible conclusion: Dave, you are bollox.

    • What you describing is not then intrinsic to the ice / espresso process.

      You may be getting some kind of off-taste, but your conclusion that the espresso is “shocked” by ice does not seem well thought out.

  7. AndyS says:

    Nice job of testing this, David — although it’s unlikely that one experiment will put the issue to rest.

    I assumed the reason for the off-flavor in ice “shocked” espresso (a silly expression) was that near-instant cooling retained more CO2 in solution than would otherwise remain. The CO2 lowers the pH and alters the flavor perception. (I don’t know this, it’s just a theory).

    It is possible that letting the beverages sit for 10 minutes allows some of the excess retained CO2 to come out of solution and therefore mitigate the off-flavor; I admit this is wildly speculative.

    It would be interesting to taste the ice “shocked” espresso immediately to see if you notice anything different. If you taste nothing unusual, perhaps your espresso is “bolder” than most and doesn’t “shock” so easily. (How’s that for a scientific explanation?)

      • AndyS says:

        1. Same test as you did, but wait only a minute (serving time in a cafe) before tasting. Don’t stress about the temperature difference, just try and look for “shocked” off-flavors.
        2. You might also try it with very fresh coffee, which presumably has a bit more CO2 in it than your normal beans.

        I just compared two sides of a split shot, one side pulled over a 22g ice cube, the other side diluted with 22g of water. After waiting for them to reach approx room temperature, I didn’t not taste any weird off flavors in the iced side. The coffee was a really nice Intelly Burundi that was 3 weeks out of the roaster. For this little test, bollox.

  8. J says:

    very interesting! What about the other spectrum – the hot shock?

    A hypothesis/myth is that an Americano where hot water is poured on top of the espresso “shocks” it (or burns the oils in the espresso), while pouring the espresso on top of the hot water is more allowing (probably with pouring up the water first, you let the hot water rest)..

    have you done that test already?

  9. Howard says:

    Re: The ‘Hot Shock’:

    Definitely this makes an enormous difference! I do this every barista course I teach and everybody – even a coffee newbie – can immediately tell not only that there is a difference, but that water first is very definitely better than the other way round (and I don’t say a word until they’ve decided for themselves!).

  10. J says:

    Howard, I thought so.. This test must be more relevant as well, since I don’t understand in what context anyone would dream of pouring espresso on top of ice 😉

  11. factchecker says:

    One of the interesting articles I read on the internet about the topic, its a shame most folks randomly ask questions a few times and don’t cover the topic, the idea came about when espresso is served in a cup that isn’t cold to prevent it from cooling, however nick and others may have used that excuse because of the ghetto latte misnomer, in which patrons do espresso over ice and add mikk, an americano iced would dilute the espresso and likely cool it more slowly , however this would also allow for gases to escape since molecules are moving, the ghetto latte is a myth, orginally espresso is served hot with steamed milk, the pricing based on the amount of steamed milk which can vary in size and area, a latte which is milk really generally would be the most expensive beverage then say a macchiato, coffee shop owners then decided to remove the steamed milk, and call any espresso beverage over ice with any amount of milk a “iced latte”, is a shot of espresso with non-steamed milk a latte, no so how could it be a iced latte, let alone a macchiato.

    It may be hard to test, perhaps an alternative to ice should be used, maybe a cool can surrounded by dry ice, too exotic? but then espresso machines are already exotic and techniques maybe not so but even still you get the concept, I think it depends on the barista, timing,type of coffee, amount of ice,etc

    • chris says:

      your head spins. mouth moves before engagement. more thought than substance. slow down, think….you may be on the right track?

  12. John says:

    Espresso immediately over ice makes it VERY bitter. I order and make iced lattes all the time. Try this test and you will see a huge difference:

    The right way to make an iced latte is to pour the espresso into chilled milk, then add ice. The latte will will be chocolaty and delicious.

    The wrong way to make an iced latte is to have ice in the milk, or even worse just ice and add milk last. The latte will be extremely bitter and taste like ass. I can always tell when it was made this way, and I return the drink and ask for it made properly.

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