Hi y'all,

I am using the Artisan software for monitoring my roasts. As you may know, Artisan "evaluates" roast phases; for cooling, it declares something like "Fracturing" and "Sweet". I realize that these evaluations are subjective at best, but they indicate to me that the cooling process my have a noticeable effect on the flavor profile.

However, I am having a hard time finding decent information on the cooling process. All I can find is that it is important to cool beans down to ambient temperatures within 3-4, or so, minutes. But that just tells me the time span from the dumping temperature to ambient. I'd be interested in more details. After all, it's no good knowing that a roast took 12 minutes without also knowing the exact profile.

Is there something like a cooling profile one should aim for? Is there a specific temperature the beans need to be brought to as quickly as possible? I would assume that the Maillard reaction should be stopped as quickly as possible, so would it be beneficial to reach ~150°C as fast as possible? Any other temperature threshold that is important?

In my setup, I often reach ambient temperatures within 30-45 seconds (when it's cold outside). I have not observed any fracturing and wonder what it would take.

Thanks very much in advance.

Cheers,
MM

The conventional wisdom is that beans cooled too slowly will taste flatter than those cooled quickly. This idea originated with the roasting design changes made in the 1920s and 1930s. Given how long the idea has been around, I'm guessing it has been tested and confirmed; but if so, I am not aware of it.

If you feel like doing the honors: split a finished roast, cooling half the beans fast and letting the other half sit. Test if you can sort five cups, two brewed of the slow cooled, and three of the fast cooled, when tasted blind. That would be a 1 in 10 chance of doing it by accident.

People did experiment with ultra fast cooling in around 30 seconds. They reported cracking damage to the beans; and recommended against it.

As far as I know, this idea has not been tested. It's absolute doctrine for no reason but superstition.

The responses so far don't make me feel so bad for not finding any decent information. But then again, I do not have ready access to much of the primary literature in the field of coffee roasting.

A priori, I do accept that slow cooling can lead to flat taste. After all, cooling is just a different manifestation of negative RoR, and that isn't desirable during the roasting process. So, by extension, it shouldn't be desirable after the beans are dumped either. That's why I surmised that one would have to get through the critical temperature range very quickly, to lock in the flavors, so to say. But what is that critical phase that, when there is a flat or negative RoR for too long, leads to flavor deterioration? To 200°C? To 150°C? Further down? What's the ideal initial RoR (or should one say RoF?) for cooling. What is 'too long'.

Unfortunately, I don't have the proper equipment to carry out a bunch of rigorous and controlled experiments. Perhaps someone else is in a better position to test the common assumptions here. But perhaps it's not that important in the end?

This is from Carl Staub 2002:
"We all look for sweetness in the cup and something we often ignore is how we cool the coffee after we
roast it. But, it is part of the process. I don't like water quenching, but I am a proponent of trying to cool the
coffee once it comes out of the roaster in four minutes or less. And why do I say that? We've done
experiments using exactly the same strategy cooling the coffee in six minutes, five minutes, and four
minutes. From six minutes to five minutes there is a small improvement in the sweetness of the coffee.
When you go from five minutes to four minutes, the sweetness in the cup doubles and there is a definite
chemical explanation for why that happens. This is due to sugar solubility. The primary sugar in coffee is
sucrose. During the roasting process you fracture the sucrose and you want to caramelize it or polymerize
it in the scientific term. But, you also have to maintain solubility. If it doesn't come out when you put water
into it, it is not going to be a sweet cup. Having the sugar there is one issue, being able to get it out with
hot water is another issue. If you cool it too slowly, the long series chain polymers, sugars, fructose and
glucose will find other constituents to link up with in the coffee and they are not as soluble.
Likewise, during the roasting process if you form molecules that are very large, they may be favorable for
espresso extraction you will get a lot of crema. Having the starches, oils, lipids, and fatty proteins in the
coffee is a very good thing for espresso. But, when you try to apply that same strategy to coffee that is
going through a paper filter, the water doesn't want to go through the filter. The larger molecules get
trapped by the paper filter and don't end up in the cup."
from SCAA Conference Transcript 2002 (Newall, Lee,Diedrich, Staub)

Thanks Ed; I didn't know about that.

Thanks farmroast. I have seen that text before, and it's the most detailed I have come across so far. But it still leaves me unsatisfied with respect to how cooling should progress, i.e., what the ideal cooling curve is. Still, it is this text that made me think, as expressed in my OP, that one should be trying to get below the Maillard reaction temperature as quickly as possible, without fracturing the beans. But then again, is a small amount of fracturing acceptable if sweetness is enhanced?

The text also hints at a dependence on the brewing method, which is fair enough, as flavor profiles of any given bean is dependent on the brewing method to some degree.

But I wholeheartedly agree with the sentiment "we often ignore is how we cool the coffee after we roast it", and that's what started my inquiry.

Here's a dissertation (COFFEE ROASTING AND QUENCHING TECHNOLOGY - FORMATION AND STABILITY OF AROMA COMPOUNDS) that looks at the effect of different cooling methods on degassing and loss of aromatics. See chapter 6 specifically.

Very good reference. Certainly a good place to start. Thanks so much!

This is of great interest to me as well. My favorite coffee roaster here in town does 25 pound batches in a diedrich ir12. He dumps the beans just as second crack barely becomes established. Charge 440 deg/min air, Yellow 6min/half air, 1st crack 11:30/full air, dump 450 deg 15:30.

I used a stopwatch on a recent visit to time the cooling of a batch of Colombian coffee and second crack continued to patter rapidly yet lightly for one minute while the beans were in the cooling tray. It took 10 minutes for the beans to cool to room temp.

I noted no divots or oil on the beans.

I took a sample of the same batch home and the aroma was as sweet as opening a box of fine chocolates. The flavor was sweet, lush, and delicately acidic. With respect to origin, it clearly tasted like Colombian coffee. This was on the first day. I sampled this roast over a few days and it was excellent, with just a very little oily sheen developing on day 3.

I will be sad when this roaster retires. So far, I cant find coffee this good anywhere else.

I try to emulate this cooling technique on my small home roasts by delaying any really fast cooling for about a minute after dumping the beans. I get good coffee, but not as good as his.