Anyone willing to share their list of do's and dont's for preserving acidity in a given bean? Not at the expense of developing roast defects such as underdevelopment, of course. Of particular interest to me are the following factors:

1. Charge temp; high/low, and the effects

2. Roaster preheating, or lack of preheating, and the effects

3. Other tips based on long time experience of other pro and home roasters

The points you're looking for input on are all quite roaster specific. I'd recommend finding the points at which your roast phases are around 5-3.5-1.5 and work from there to dial in a given bean with your roaster.

Getting to that point will be a great exercise in familiarizing yourself with the roast dynamics of your roaster.

Preserving acidity is somewhat a misnomer, since acidity is built up in the roast just as much as it's destroyed, and until later stages of dark roasting, I'd argue that the scale tips more towards the later.

The vast majority of chlorogenic acids break down even in very light roasts, being hydrolyzed not quinic and caffein acids that then go on to produce phenolic volatile compounds thru pyrolysis. Even as that pathway is ongoing, those new compounds are forming new cinnamic acids, so on and so forth.

Ultimately, it comes back to the green coffee itself, being so vastly different in makeup, it's hard to nail down specifics. It's more a matter of optimizing development time and cupping/assessing for the results you seek. But I find that I can get more repeatable results by mapping in and having my ET's and MET's more level towards the tail end of the roast, not making drastic changes in temp. But the idea of "preserving sugars" is also equally or more flawed, since even in the lightest of roasts, 97% of sucrose is degraded (and their resulting byproducts even faster and more thoroughly) and in medium roasts its around 99%. Roasting is far more necessary and far more complex than any of us can truly grasp. And by necessary I mean that you must put your roasters fingerprint on the bean. The more talk about preserving the nature of the green is becoming more and more absurd. Volatile compounds in the green coffee make up just a small component of their overall contents, yet scientists have counted at least 230 different volatile compounds alone. It only gets more complex from there. How are we to say with any degree of certainty what approach yields consistent and optimal results?

Dean,

While I can't offer specific information on preserving acidity, I can suggest that you add drying time another relevant and hard to pin down variable in your quest, as it sets the stage for the rest of the roast. Especially with natural process coffees, getting this wrong can have a big effect on the end product.

I've personally never experimented with not pre-heating the roaster, but I don't see how this would be beneficial (but honestly never thought about it so I could be wrong!) With a drum roaster, I think starting with a cold drum would bias things heavily towards convection, at least until the drum heated up. Depending on how long your particular roaster takes to heat up, by the time the drying phase is over the drum might be sufficiently hot to start conductive heating.

One last thing that just occurred to me -- as I'm sure you're aware, lighter roasts often need more "rest" time before they taste their best. One thing I've noticed is if I have a coffee that seems too light or underdeveloped after my usual 5-day waiting period (for espresso at least), waiting another few days will almost always improve things, but the acidity is still very prevalent. When working with this year's Guatemala Candelaria I found that finishing earlier than I normally would (217c on my TC's) and waiting a minimum of 7 days yielded an amazing cup of coffee

Good luck,

frank

Easy. To increase perceived acidity shorten over all roast time, especially after crack. Try a 330, 330, 130 roast. Or a 5, 4, 1 roast. Keep things light.


What type of roaster do you have?

Hello Dustin,
What is a 330, 330, 130 roast?
What would be your rate of rise for the development and what would be the finishing temp?
Regards
Martin

mfortin wrote:What is a 330, 330, 130 roast? What would be your rate of rise for the development and what would be the finishing temp?

A 330, 330, 130 roast is a 3:30, 3:30, 1:30 roast without the punctuation -- which probably doesn't answer your question. The numbers represent the elapsed time for the Drying, Ramp, and Development intervals. So:

• Three minutes and thirty seconds (3:30) from Charge to End of Drying (generally 300F);
• A further 3:30 from End of Drying to beginning of First Crack (1stCs);
• Another, final 1:30 from 1stCs to Drop; for
• A total elapsed roasting time of 8:30.

Accurate rate of rise (RoR) can't be calculated without knowing the roast milestone temperatures. But you can come pretty close by estimating temps for Charge, Turning Point; 1stCs, and 1stCe based on common values.

In my opinion -- and it's just my opinion -- that's a really lousy profile for an ordinary drum roaster.

Better and more doable for a light, bright roast, would be 5:00, 5:00, 2:00 to a bare "C" finish, about 5sec beyond 1stCe (probably 210F ish).

I find the best balance between bringing out the "acid notes" of fruits and florals AND holding those flavors long enough for the roast to rest and about a week thereafter involves a slightly extended Drying interval, a fast Ramp, and a slow Development into the C+ range. However, it is a balance. The best technique for acids is "short and fast," while the best technique for stability is "low and slow."

You have to be careful not to take the roast too slow through Drying and Development. Depending on the bean, sometimes you have to make allowances for the purpose of the roast in the sense that beans roasted expressly for espresso should be taken to a slightly deeper finish.

Try a 300F Charge, then the following profile: 6:00, 3:45, 3:30 to C+; around 422F for a generic all-purpose C+, or 415F for brew and 427F for espresso, with a few extra seconds for the espresso's Development. A slowish Development RoR is a little tricky to state and to due, because the temp curve will inflect sometime during rolling 1st, as exothermia ends. You want to keep enough RoR to avoid stalling (at least 2F/min), but not so much as to go too fast to the end.

Once you've established the temperatures for the milestones for a given bean, draw an ideal plot on graph paper; figure out the flat RoR for each interval; charge your roaster; and ride the power and air to roast as close as you can to the profile. Then rinse and repeat cup and tweak.

Rich

Rich,
I think that's a very well expressed and helpful answer.

Dick

One of my favorite things about this place is the divergence of opinions on what is "too dark," "too light," "underdeveloped," "grassy," etc. I don't know why, but somehow my faith in human beings is renewed when I see genuine differences of opinion that don't escalate into hostility.

Not that it's happened yet on this thread, but the use of the aforementioned word "underdeveloped" put me on alert for some possible back and forth.

Dean I can tell you with certainty that there's no consensus among members here as to the difference between "underdeveloped" and "bright" or "acidic." Sure, they might agree on the extremes, but fans of the nordic roast style are not well represented here and are sometimes persecuted for their beliefs

Hey Martin,

Go as slow as you can twards the end of the roast. This profile works really well on Geshas. But when it comes down to it, it really depends on the roaster/bean/and person. Different roasters transfer heat differently, and different beans receive heat differently. So while a profile might not work for bean b, it could work for bean A. One thing I can tell you for certain, is take peoples advice here with a grain of salt and test things out for yourself.

Anyway, a shorter profile generally yields more acidity for me, especially a shorter finish phase(first crack to drop).