Development time as a ratio of roast time by Scott Rao - Page 11

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
Dregs
Posts: 69
Joined: 10 years ago

#101: Post by Dregs »

boar_d_laze wrote:If you think of Drying and Ramp as separate intervals you may find it easier to control the roast.

For instance, you can go low power and air through Drying, and increase both for Ramp, maintain a declining RoR, and hit 1stCs in the mid nines to low tens. That's a good elapsed time to enter 1stC because it allows you to hit the desired finish -- which is really just the range of C+ -- in a time which comports with the 20% - 25% range.

My experience is that by manipulating Drying and Ramp differently, I can balance the amounts of fruits and florals in the roast against the time they'll stay stable as the roast ages. Dry too fast and Ramp too slow, and their intensity is maximized, but they fade quickly. Dry too slow and Ramp too fast, and the varietal characteristics are comparatively flattened but the roast will retain its distinctive character for a long time as it ages.

Also, it might help to think of Development as two -- or even three -- discreet intervals. In order to maintain control of Development you have to allow for momentum and exothermia, and lower your heat and increase air in anticipation of 1stCs. You can't wait for the first snaps, you have to be at least 10F in front of them -- I typically go with 15F - 20F.

If you aren't pumping too many therms into the drum and are using enough air, when exothermia ends -- about half way through rolling first -- you'll see an inflection on the plot as RoR drops. You'll have to stay on top of the gas (or power) to make sure it doesn't drop too much. You're probably looking for an RoR of 6F - 10F from a few seconds after the inflection all the way through the rest of Development to Drop.

It's the entire period going from anticipating 1stCs all the way through to Drop where real time BT plotting really pays off.

If you want to try "one profile to rule them all" which will work with a roaster the size of yours, and follow the general tenets of the style Scott wrote about, try:

Charge at 300F, very low gas, low air; 6:00 (total) Drying (to 300F), after TP, use enough air to maintain negative pressure in the drum and enough gas to hit your time; 3:45 Ramp (to 1stCs), with slightly more air; 3:15 Development (to C+, about 10F shy of 2dCs), with quite a bit of air as a starting profile, with an eye to what I wrote about anticipating 1stCs, and tweak from there.

The real power of that profile is not its universal perfection, but that it's a plan which fits the numbers and which is easily adjusted. You can go from a 13min ET to 11:30 or 14:30 very easily. If you want a 25% (or any other desired percentage) Development ratio, it's easy enough to plan and execute. There's no reason to dance around with "almost."

Here are three more maxims to go along with Scott's Commandments:
  • I. It's better to use your roaster to cooperate with bean chemistry than fight it.
    II. Plot your ideal profile before roasting, and then execute it.
    III. Roast on purpose.
Rich
Exceptionally helpful post. You provided the practical, "how to" details that are missing from the book. Can't wait to give it a try.

Thanks,

Dregs

osanco
Posts: 121
Joined: 11 years ago

#102: Post by osanco »

+1 BDL -and for the record, pretty much what I've been doing since the first time I learned this from you. :D

The Tanzanian I did yesterday is cupping great this afternoon, btw. Nutty, sweet, with great body and aftertaste, and enough acid to make it interesting.

Scott is pretty complimentary of smaller roasters. I wonder if the agility of smaller machines allows us to roast successfully in a variety of fashions? Or to put it another way, could it be that larger machines with their larger roasts are more susceptible to the kind of roast defects he is cautioning against?

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boar_d_laze
Posts: 2058
Joined: 17 years ago

#103: Post by boar_d_laze »

Hi Steve,
osanco wrote:+1 BDL -and for the record, pretty much what I've been doing since the first time I learned this from you. :D
Oops. :lol:
Scott is pretty complimentary of smaller roasters. I wonder if the agility of smaller machines allows us to roast successfully in a variety of fashions? Or to put it another way, could it be that larger machines with their larger roasts are more susceptible to the kind of roast defects he is cautioning against?
It's a little hard to tell what he's thinking, because he is vague. It seems to me that Scott is mostly looking at roasters in the commercially viable "shop roaster" range of around of 3kg up to around 12kg. Ed (farmroast) -- through their mutual Cropster association -- might have more insight.

That said, I think you're right that there are a group of roasters at the smaller end of the shop roaster, say 1lb to 3kg, which offer enough heat and air and a small enough load that you get a little extra room to improvise within the tricky moments.

One of the things I've noticed in reading the academic literature pointed to commercial roasting on a larger scale is that a lot of the numbers don't work out as well as they should for my smaller roasters if they were universally correct. In the type of roasters Rao called "classic drums" (nice to have a name), I think the part played by the ratio of volume to lateral surface area is usually overlooked.

Rich
Drop a nickel in the pot Joe. Takin' it slow. Waiter, waiter, percolator