Sour Tasting Coffee Roast - Why?


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May 26, 2018
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I have a limited number of roasts under my belt, with my Behmor 1600 Plus. I completed a roast Saturday PM and made a cappuccinio this Sunday AM. I encountered sour notes. I am trying to determine whether this was due to: a) the coffee being too fresh (needs to rest 3 days?), or my roasting profile, or the end roast, or my barista technique (doubtful).

FYI, I have fairly good espresso technique and consistancy (been pulling regularly quite tasty shots, using roasted coffees acquired from a local coffee roaster), so I am confident that the sour notes are not due to my barista skills (although I do know barista techniques to correct for sour notes, which I have not yet employed). FYI, the shots ran within a reasonable time and looked good through my bottomless PTF.

The Roast was ended as either a Full City + or Vienna, based upon been colour and appearance (using the SweetMarias roasted bean photo chart). I used Brazil Bourbon Santos (50%, Samatra Mandheling (25%) and Guatemala Antigua (25%), blended prior to roasting. Total of 110g coffee. The roast profile ended up something like this, using a thermocouple probe placed close to the drum:

1 lb buttom setting on P5, to set to manual, all to allow full time flexibility.

On P5
- 3 min elapsed - 210 F
- 5 min elapsed - 280 F
- 5:49 elapsed - 300 F
- 8:49 346 F - possible FC (I am hard of hearing)

So went to P4 for Roast Development
- 10:30 still hovering at 348F

So went to P5
- 10:48 to 13:14 peaking at 385F
- SC at 13:14
- Hit “Cool” - 2 minutes in Behmoor with door closed
- then stopped and transfered to collander with airblower (clean shop vac in reverse), for rapid cool down.

Roast had sour notes. Just didn’t like the flavour.

FYI, had this same coffee blend from the same coffee roasting company, with the Brazil ordered as “medium roast”, the Sumatra ordered as “dark” and the Guatemala ordered as “dark”. So 50% medium and 50% dark. And liked the taste. Nice complexity. Nice sweetness. No sour notes.

Also FYI, the blends I have been ordering have tended to be darker. Likely Vienna to French in these blends. Yet I have had “medium” roast blends from another local roaster and quite liked those.

Please comment on the roast profile. And the reasons for the “sourness”.

Thanks for you

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Hey there... welcome to the forum. Sourness is often caused by too weak of extraction - the first thing I would try to troubleshoot by increasing the amount of coffee a few grams. Its at least a parameter to play with if you experience sourness. Coffee lets off a LOT of CO2 just after roasting. Watch your shots, when coffee is pressurized in the portafilter it will often come out fizzy/fast due to the extra gas when 'too fresh'. Each coffee takes a different amount of time to mature in flavor, I find I like coffees at least 3-5 days off roast date. For example, my espresso blend taste best to me after about 5-7 days. Looking at your roast data it does appear your roast stalled a bit around FC. Simply meaning it stayed at the same relative temp for a period of time, you want to avoid that as well as temp spikes. IMO the 2 degrees from 8:49 > 10:30 is a long time at the same temp. Stalling can cause some odd flavors in your roast. The best advice is to taste it every day to see how it taste. I think overall you have a good grasp of the basics of roasting.
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Thanks for your fulsome advise, Musicphan. Will be re-tasting that coffee, and roasting some fresh coffee, this weekend.

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It should also be noted that sour notes in coffee speaks often to under-roasted coffees. You mention SC at 13:14, do you have the temp recorded there?
Also what was your dump/end temp? Understanding the Behmor cooling cycle, just curious about the end temp.
If coffee is under produced it will taste sour because the fruity acidity comes out first. ... However, for these sour notes to taste good in a cup of coffee, they need to be balanced with the sweetness and even some bitter notes that develop later in the brewing process.