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Sour Espresso (Cappuccino) from Recent Roast: Why?
JCafe
Folks

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 your help.

Appreciatively

JCafe

PS

Just ordered a “HeatSnob” so I can better see my roast profiles, and understand what I am doing right or wrong. Also ordered Scott Rao’s book.
ChicagoJohn
A "sour" taste typically comes from organic acids, and as a roast proceeds beyond the end of first crack at gradually decreasing rate-or-rise, the acids are degraded, the acidic tastes decrease and the sweeter tastes increase -- until you get into second crack at least. It sounds to me like your roast may have been terminated on the light side, and you could try extending the time and a higher final temperature.

Temperatures will tend to be method and device dependent, the important thing being repeatability. That said, I'm using an air roaster, hitting 350°C at around 7:30, seeing first crack in the 380 - 395°F range starting at around 9:30 and roasting a medium level to 410°F at about 13:30. The temperatures you cite are quite a bit lower but may be typical for the Behmor 1600. Maybe roast color would be a better indicator of where you've ended up than absolute temperature.

Another thing I've noted is that at equivalent coffee:water ratios, espresso extracts a lot more acid from a roast than drip does. For a very light roast I did recently, I got a pH of 5.3 for a double espresso draw and 6.3 from a drip brew versus the water I was using at 7.4. The espresso was very sour while the drip brew was drinkable but had lemon citrus to it. I think this happens in my processes because the espresso water temperature is higher and the grind is finer.

I doubt if the resting time is a major contributor to your acid issue.

Just finished my experiment -- the light Yirg Z roast to 404°F at 12 min; double espresso from 15 gm of the product of a 7 setting on a Rocky grinder were compared with same at 410°F 13:30 after cooling the results to room temperature. The pH values were 5.3 and 5.6, respectively with the lighter having an almost vinegar level sourness and the darker a mild grapefruit level citrus residual tartness. It may not seem like a pH difference between 5.3 and 5.6 would make much difference, but since pH is the exponent of hydrogen ion concentration, the 5.3 pH had about 2X the concentration of acidic hydonium ions as the 5.6 pH (10^-5.3 / 10^5.6 = 1.997) So tomorrow morning I'll give it a try in my soak / cone brewing process.

So I would think your results might improve with a little more time and final temperature.
Edited by ChicagoJohn on 08/01/2018 9:42 AM
So many beans; so little time....
JCafe
Very much appreciate your solid response, ChicagoJohn. Thanks as well for you testing. I will try for abit longer roast time, higher temp and slightly darker bean.
ChicagoJohn

Quote

JCafe wrote:

Very much appreciate your solid response, ChicagoJohn. Thanks as well for you testing. I will try for abit longer roast time, higher temp and slightly darker bean.


Please be sure and post your results here. This is all very much a learning process for me.

I made my morning coffee today with the latest, longer roast and there was a vast improvement -- reduction in acidity and tea-like flavor and body, and increase in complexity and sweetness. Looks like the same profile I've use for Yirgacheffe for a couple of years doesn't do well for this latest purchase, but at least I can improve results by extending time and temperature, and I'll go a bit further and see what happens.
So many beans; so little time....
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