Is "sour" espresso a roasting defect - or a brewing error?

Discuss roast levels and profiles for espresso, equipment for roasting coffee.

#1: Post by GDM528 »

In the context of pulling espresso, can sourness be traced back to the roast - or it largely just a tuning problem with the shot?

Made a dumb mistake at a coffee shop recently: bought a bag of well-regarded professionally roasted coffee; seemed like a safe bet... then ordered a shot of espresso from their professional barista of the same roast I just bought... It was OMG-sour, Third Wave-run-amok-sour. Note to self: try a shot first, then buy the bag... or not.

At home, I was able to tamp it down a bit but never able to fully vanquish the sourness. This left me wondering how they pulled off this roast. If somebody were to ask me for a sour roast, I wouldn't know what to do. Not that I ever want to roast sour espresso, but if I can learn exactly how to make it that way, I can be better at avoiding it.

It was a City roast specifically meant for espresso, but there is also a version roasted for drip - perhaps that's a clue. Are greens suitable for drip/pour-over potentially too acidic/sour for espresso?

They call it a "S.O. Blend" (isn't that an oxymoron?) from Central/South America and Africa. Are greens from Africa more prone to sourness?

They use a big-batch drum roaster, so perhaps the drying time and browning phase was protracted. If I completely caramelize all the sugars, can the reduced sweetness lead to sourness?

And finally, is this just a shot-tuning problem for both the barista and me? Should I have kept going with a hotter brew temp, finer grind, slower pull, lower brew ratio?

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#2: Post by Jeff »

I think it can be both. There's certainly an art to being able to roast coffee well. I'm far from an expert (OK, my roasting skills suck), but my guess is that either direction from "medium" is more of a challenge to do well. Luca recently wrote that he believed that roasters adopting newer technology let them be more consistent in their roasting. I agree that doesn't make them better, but does let them better understand and control the process. Today's "medium" is the "light" of a decade ago. That unfortunately doesn't mean that all roasters have mastered the craft.

Luca also mentioned that he understood that Tim Wendelboe's "espresso" roast is now lighter than his "filter" was some time ago. I've had both with the same green and both are significantly lighter than typical US practice for filter. They're both enjoyable as espresso. It is mainly that the "espresso" is a little easier to extract well.

On the brewing side it is just as challenging. 10-15 years ago, it was rare that there was a single-origin espresso as an option, even in roastery's cafe in San Francisco. Baristas would look at me funny when I asked if they had pulled some single-origin filter offering as espresso. These were baristas with full-on handlebar mustaches and tattoos. Not that appearance means anything, but it seems that was near the peak of barista as a craft. Since then it feels like it has slowly become more of a service. I no longer trust a cafe to highlight what a coffee is capable of.

I'd cup what you've got in front of you. If it is sour, then it is at least partially in the roast. If you get a reasonable balance, then the question becomes whether to just enjoy it as filter or try to tackle it as espresso.

Light-roast espresso is, to me, a different drink than classic espresso. If you're expecting the kind of flavor balance of a typical "chocolate and nuts" espresso, it is very different. As much as some call it "battery acid" in comparison to what they are used to, a lot of the classic espresso blends taste burnt and overwhelmingly bitter going the other way around.

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#3: Post by baldheadracing »

Just an anecdote:

There's a roaster (that I won't name as I haven't had their coffee in years) whose every roast that I've had would curdle milk. Extremely hard-to-grind beans that were probably dropped a very few seconds into first crack. One of their coffees had "Quince" as a tasting note. (Quince fruit is extremely tart.) The owner of a local café that pulled a shot of that coffee for me (after multiple attempts) used an MVP Hydra with long pre-infusion. It was good and interesting so I bought a bag. At home to match the Hydra shot I had to use a (known-good) sloped single basket, dose 6g, grind very fine to get a long pre-infusion, and pull around 6 bar max to get about 30g out on a manually-retarded spring lever (Elektra Micro Casa a Leva). On the pump machines that I had back then - battery acid and pucker/shrivel your mouth sourness; undrinkable sink shots. On the Elektra - an explosion of not-so-sweet forest berries coupled with pleasing acidity and a hint of Quince in a tea-like drink.
-"Good quality brings happiness as you use it" - Nobuho Miya, Kamasada

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#4: Post by luca »

Yeah, as Jeff and Craig have said, it's a bit "how long is a piece of string"?

Whether or not something is a "defect" or an "error" depends on your expectations and your frame of reference. The specialty coffee world has become bigger and more diverse, and you'll see that people reject basically any "rule" that you put in place as to what is defective or what is not. Which is to be expected - most people that write about coffee write about what they have to sell, and you can hardly expect they will be critical about it: they'll just tell you about what they think are the good aspects and stay silent about the bad. OK, that's fine, but the corollary of this must be that it's perfectly legitimate to decide what you like and what you don't.

So let's take it as a given that this coffee is too sour for you. I suppose it's probably marginally more likely to be roast than brew, but, as Jeff has said, fixing that as a roast defect will probably create other problems; often bitterness, sometimes dulling of aroma, sometimes astringency, sometimes imposing toast type aroma on top of everything else. So you have to pick your poison. Personally, I'll take high acidity over any of those other things any day of the week, and I don't think that standard espresso roasts are enjoyable. YMMV.

But let's look at things practically, in terms of "what are you going to do?" You have the coffee already, so changing the roast is out of the question, so we might as well look at brewing. One thing that you can obviously do is to look at your water and supplement carbonates and any other anions that will buffer the protons. This does make a difference, and I think 3WW espresso formula has something like 3x as much buffer as their regular formula. Because, of course, you have so much less water in espresso than in filter coffee, so you need a much higher concentration of anions to have the same buffering capacity.

Next, the orthodox thinking seems to be that the acidity is super easy to extract, but other things are not. So basically, the idea goes, as soon as you have a little liquid making it through, you're going to have a lot of acidity. I don't know how much I really buy this; it probably doesn't hold true in all scenarios, but there are a few things to look at:
1. Look at your extraction yield. Some burrs and some baskets simply give you extraction yields that might 14% or 16% instead of the 22% to 24% that will probably taste better with lighter roasts. But if your coffee has been roasted to bake out the acidity, you might find that increasing extraction yield increases extraction of the undesirable characteristics of these roasts.
2. Look at your shot style. There are basically two approaches: you can go with an oozy slow flow rate shot where maybe you can keep it so concentrated that the strength sort of overwhelms the acidity. Or you can go with a faster, turbo style shot, where you are trying to have a weaker, but higher extracted, shot where you bring out more aroma to counteract the acidity. Again, there are stylistic choices, and you have to be a grownup and acknowledge that you don't just get to tick "yes" on everything in the desirable traits column. If you go for the show flow rate shots, you are going to sacrifice the distinctive aromas of the green for generic chocolatey type flavours. If you go for the turbo style shots, you are going to give up strength. Choose.
3. Temperature. I'm not overly au-fait with using temperature to control acidity, but it may be non-linear. Try super cold, too. Like 80C. Again, you pretty much can't change things in isolation. You may find that super cold temperatures mitigate the acidity but also leave the shot flavourless.

On your other questions:
1. SO blend sounds stupid to me. It actually sounds like it is a blend of things from the same origin. Like if you did two roasts from the same origin and blended them, or if you had two different coffees from the same farm. Or maybe two farms in the same country.
2. Green from Africa often has high acidity. But why not ask the question "are greens from outside Africa more prone to have dull and lifeless acidity?"
3. AFAIK, acidity varies inversely with total roast time, at least in regular roast parameters. So whatever you are surmising about sugars, sounds like you are probably using it as a proxy for roast time. And I'm probably using total roast time as a proxy for some subset of roast time; like if you spent an additional minute with the BT below 100c, maybe that would have zero impact on acidity, for example.

FWIW, yeah, I've had roasts that I've regarded as too light for espresso.

Anyway, there are a few thoughts.
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#5: Post by Milligan »

Would perhaps one say it is a combination? Picking a high acidity coffee and cupping for sour/tart then roasting lighter to accentuate that characteristic would certainly lead to a sour espresso if one was trying to get that.

I'd think the easiest path to sourness would be by brewing (we can all dial in a sour shot with any bean by cutting it short), but to have a shot that is innately sour and hard to dial out the sourness without losing character would have to be a deliberate green and roast choice, correct?

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#6: Post by Peppersass »

Yes, it can be both.

If the roast was properly developed, you or the barista should be able to tune the espresso parameters to minimize or eliminate sourness. For medium and light-medium roasts, this usually amounts to one or more of the following: grind finer, reduce dose, pull longer, increase temperature. For light and very light roasts, you may have to resort to grinding extremely fine and using long, slow preinfusion and possibly reducing dose, pulling longer and increasing temperature.

If the roast was underdeveloped (and likely very light), the above techniques may not eliminate sourness, no matter what you do. Essentially, the bean isn't fully cooked and the sugars haven't been carmelized. You won't get any sweetness and probably the cup will be sour. But usually there will be other tell-tale flavors (roast defects) reveaing that the problem is the roast and not the extraction: grassy, vegetal, hay-like, bread-like, etc. If you're tasing those flavors, it's the roast.

If you want to avoid these roast defects, make sure the roast is fully developed. With my Ikawa Pro V3, I've found that the Espresso I profile works well for most coffees, but I always drop manually rather than using the profile's roast end time. Since it's often difficult to hear or properly mark the beginning of first crack, I focus on total time and drop temperature. If the roast turns out to be too light and underdeveloped, I'll increase the drop temperature, which will increase total roast time. If the roast is a little too dark and the acidity and sweetness I'm looking for are missing, I'll drop sooner at a lower temperature.

If you can't fully extract a properly developed light roast due to limitations of your espresso equipment, roast a little darker.

In my experience, African coffees do tend to be more acidic than coffees from most other regions, but I wouldn't characterize it as sourness, and I don't think that underextracting them results in any worse sourness than underextracting any other coffee. With enough experience pulling shots, you can tell the difference. To me, "acidity" means brightness, which is something I seek and really like in a coffee, whether it's pulled as espresso or filter. I'm more of a fruit guy than a chocolate and nuts guy, though a little of the latter is fine as long as the former is most prominent. If the taste is unpleasant (mouth-puckering lemon juice), then it's an extraction or roast issue.

Astringency is another thing not to confuse with sourness. Sometimes a little astringency is a good thing. For example, Kenyan coffees often finish with a bit of blackberry-like astringency that's characteristic of the varietal. But in many cases astringency is a mouth-puckering roast defect that can be easily confused with sourness.

I don't agree that it's easier to avoid sourness with espresso than filter. I think it's the opposite. Light and very light roasts are generally easier to extract as filter because the water contact time is almost 20x the water contact time of espresso. To pull these roasts as espresso you'll probably have to resort to the advanced techniques described above. Further, with espresso being about 10x more concentrated, any sourness is going to be greatly amplified.

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#7: Post by Almico »

I'm not a big fan of light-roasted espresso so I really don't have a dog in this, but as far as SO blends go, I would guess most SO coffees are blends. Not necessarily blends of terroir, but certainly blends of variety. And coffee variety has much more to do with the characteristics of a coffee than the country where it was grown.


#8: Post by tompoland »

Assuming its brew (which I would guess is most of the time) here's a quick troubleshooting checklist (make sure your machine is clean first ... VERY important).

Too acidic or sour then try:
a. decrease grind size (make your grind finer)
b. increase ratio of grams in, to grams out
c. try a darker roast bean
d. reducing the dose in the basket if too full (five cent test)
e. check for scale build up in your machine (if in doubt, descale it like a demon)
f. the last variable to change is temperature. Increase brew temperate (if can't adjust then ensure your machine has fully warmed up)
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#9: Post by ojt »

Good old disccussion on sour vs "traditional", "third wave" vs traditional, etc. Or at least this very easily gets to that point. There sure is a trend now, and has been for a good while(?), favoring lighter roast and fruitier taste notes.

I personally seek those bright acidic tastes. I have yet to find an origin / bean that would not be suitable for espresso. Only a couple of times have I found a roast that I deemed almost too light for espresso. Most light roasts, even those deemed "nordic light" are actually in my opinions quite a bit in the "omni roast" regime, meaning to me that I can extract them well in both espresso and filter without too many tricks.

I have some limitations with my Pavoni + Kinu combo, mostly because of the Pavoni, even if I've gotten pretty good at it. In my experience one of the key factors in extracting the very light roasts is increasing preinfusion time and even using the "blooming" technique. It tones down the acidity. Temperature is a bit of a separate factor in my opinion but the lighter roasts do tend to need a higher temperature, but not always. I think the grind and the brew time, or amount of water, are more important.

Some roasts have been really under developed and had grassy vegetal taste notes no matter how I prepared them. In those cases it is the roast, not brewing technique. A good idea given above is to either cup the coffee, or just make a frenchpress of it, or any other brew method, or all of them. Testing different methods gives an idea of the potential of the coffee. If for example the coffee is under developed you will get the grassy taste with all methods. If it just tastes a bit bright in frenchpress you know it's OK but might need to extract more in espresso.

Anyway, just my experience.

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#10: Post by bean2friends »

My first experience with a coffee I bought for espresso, because it was marketed as espresso. I also noted that there were a number of folks here on HB who really liked it. So, when I got it and saw how light it was, I had serious doubts. And, my first taste of it, I didn't like. Well, I had it now, what to do? I wasn't going to pitch it. Finally based on advice I gleaned here about what to do I turned up the heat quite a bit. Normally, I brew my espresso at 93C. I turned it up to 97C and found I liked this cup very much. It was unlike anything I've ever had as espresso, but I'd buy it again.