Carneiro wrote:
I was curious as I've roasted some batches on a Diedrich IR-12 (1200 g batches). But in general, at the IR-12 or now at my Quest M3, I hardly go over 207C, 2:30 to 3:30 from 1C to the end, but in general I get 16% loss too.

I think the way Steve advocates his roaster can be used to lighter roasts, finishing below 210C in a short time. Of course it depends a lot on the batch and coffee (I'm always talking about Brazilian as I can't roast another bean!).

Márcio.

With my IR-1, this would make only a very small difference in roast timing. I've been reducing the gas significantly at the end of the roast, when the roaster gets to around 405F. Yesterday, I cut back from around 6 or 7" of water column to around 4" at this point. Even so, it only takes about 30 seconds to go from 405F to 420 or 422F, with the reduced gas setting and full (80%) air flow through the drum. If I was to dump the beans at 210C (410F), that would shave at most 20 seconds from the roast time. I doubt that the roast level or weight loss would be greatly effected, and I'd still get nowhere near his proposed roast time for a fast finish after the onset of first crack.

I'm hitting first crack at between 370 and 375F; it is the portion from the onset of first crack to around 400F that takes the longest time.

My opinion, which could be wrong, is that Diedrich wanted the IR-1 to mimic the roast profile behavior of their larger roasters, however that result did not actually happen in the production models, at least if my roaster is representative of the rest of the (small number of them) that have been produced at this point.

ken

Ken,

I'm curious: how long does it take after you dump the beans for them to reach ambient temperature?

Thanks,

dan

Dan,

Diedrich talks in terms of that needing to occur within 5 minutes. My experience with this roaster is that it takes around 2 minutes for a 1 lb batch, and maybe 3, under 4 minutes, for a 2 lb batch. There are no stirring vanes on the dump tray, however the fan is powerful when the damper is set to have the fan pull mainly (80%) through the cooling tray. You need to use an impliment like the spoon supplied by Diedrich, which resembles an ice cream scoop, to distribute the beans evenly, but once done (takes 10 seconds or less) no further stirring is needed, except perhaps to aid in evacuating any residual chaff, which might be present if roasting DP beans.

Diedrich claims that you can proceed directly from one batch to the next. I have not done this so far, mostly because I'm still in the early learning phases with this roaster and I want to weigh the roasted beans after each batch (before starting the next one) to see how much moisture loss I've had, as an aid to better learning how to use the roaster and when to end batches. The way the roaster is designed to be used, one does have the damper set to go through the cooling tray for the first 4-6 minutes of the roast, so this would be compatible with starting the next batch as soon as the drum cools down from the prior one (takes very little time, especially if roasting ~2lbs or 1kg, since your charge temperature is supposed to be around 400F in that situation).

ken

Ken,

Have you looked into the effects of rapid cooling? I have not done anything systematic, but 12-14 seconds after I dump the beans, they are at room temperature. There is no question that some additional cooking will happen during the first minute or so of a two minute cooling time. That means you need to anticipate the dump, which is hard if you are basing it on waiting till the second crack, for example.

On the other hand, maybe a gradual tail off caused by slow cooling might be beneficial?

I think one reason I've had good luck with my roaster in terms of hitting certain roast levels consistently is I don't have to allow for cooling time. If I hear the second crack starting, I can stop the roast almost instantly.

I think this matter bears further looking into.

dan

Dan,

I have visited several commercial roasting plants from the sorts of roasters that we all look up to. Their large drum roasters do not cool the beans any faster than what my Diedrich does. This is not surprising since the Diedrich IR-1 is basically a scale model of Diedrich's larger roasters.

Fast cooling could use some study, but I think it would be a study that is beyond my level of competence to complete.

My (former) 1lb sample roaster did cool the beans faster; probably in a couple of minutes vs. 3-4 minutes in this Diedrich. At this point, I believe that my results from my old sample roaster were "better" than from this Diedrich, which I would not attribute to the cooling time but rather to the roaster and roast profile. I had 7 years to learn how to roast on my old sample roaster, and less than a month, so far, with the Diedrich.

ken

I have been curious about cooling rate, particularly because I don' t have much choice with the gene cafe. I experimented with the force cool that spits it out a bit faster but then you're left juggling a scalding and expensive bit of glass. Ken, I think your roaster would be a convenient test bed given its batch size and that cooling is external. I wonder if it would be possible to come up with three different ways to split the exact same batch: a highly insulating vessel, standard down-draw and stir, and some other really fast method (spray bottle, shop vac and colander etc). Maybe this has been done and I don't mean to volunteer you but you seem uniquely poised to produce a large enough single batch. The nice thing about this way is that you know the coffee is actually identically roasted and only really needs to be half decent. It should be easy to push the cooling to the extremes on both ends and get a sense of how vast the difference is and how large the acceptable margin is.

A post from about three years back on Coffeed that did this. The results, not obtained blind, if I remember it right, supported the conventional wisdom. Cooling times longer than about four to five minutes tasted flat, and cooling times lower than a minute yielded brittle beans that staled quickly.

I think it's pretty safe to say that if you cool the beans in two to four minutes, the taste won't be harmed. If you cool faster or slower than that, they might.

kmills wrote:I have been curious about cooling rate, particularly because I don' t have much choice with the gene cafe. I experimented with the force cool that spits it out a bit faster but then you're left juggling a scalding and expensive bit of glass. Ken, I think your roaster would be a convenient test bed given its batch size and that cooling is external. I wonder if it would be possible to come up with three different ways to split the exact same batch: a highly insulating vessel, standard down-draw and stir, and some other really fast method (spray bottle, shop vac and colander etc). Maybe this has been done and I don't mean to volunteer you but you seem uniquely poised to produce a large enough single batch. The nice thing about this way is that you know the coffee is actually identically roasted and only really needs to be half decent. It should be easy to push the cooling to the extremes on both ends and get a sense of how vast the difference is and how large the acceptable margin is.

Hi Kendall,

I think I need to get to the point where I am satisfied with my basic roast product before wandering off into the weeds, as it were. One of the problems with roasting in larger batch sizes is that you have to figure out what to do with the "interim" results. I'm beyond the point where I'm "ruining" coffee, however my current results are "not to die for." I think it is going to take a few months before I am comfortable with my results, and at this point I could consider some experimentation. Notice I said "comfortable with my results." That's not the same as being "happy" or "delighted." Those latter phases might take a year or two or even more. We shall see.

ken

Sorry to hear your socks haven't been knocked of yet Ken. After 96 roasts on the Gene cafe, I still have a nagging doubt that I could do better than the internal cooling. It averages 10 min before I can get to the beans with the standard cooling and then they are still relatively warm. I wonder if that is long enough to push past the nebulous "OK region" into the "dull zone". I was fully aware of this limitation when I bought it so I can't complain too much.

If there was any way that I could dump the beans immediately or almost immediately and then cool them externally, that is what I would do with your roaster. I have never seen a Gene Cafe, nor do I know how it works, so this is probably not possible to do or you would have already tried doing it. A pair of oven gloves or large silicone pot holders would be invaluable were you to try this; third degree burns can be very nasty!

ken