I heard large-scale professional roasters do use water to do a fast cool down of their roasts. I am using a gene-cafe , and am always looking for ways to speed up the cooldown of my roasts. Does anyone have any experience with using water for cool down?

i remember reading somewhere that you can use a common spray bottle with water to shoot a fine mist on just roasted coffee to cool it down more quickly. **I haven't tried it yet. ** The trick is to use just enough to cool the beans and not have any droplets remaining. You'd probably want to empty the beans from your roaster first though.

let us know what you end up doing.
jim

No - most professional roasters do NOT use a water spray. There are some instances where some professional roasters operating in non-air conditioned facilities in a very hot climate may do this on the hottest days but it is (or should be) done with with extreme care. The spray should be a very fine mist and of very brief duration - so brief and so fine that it immediately vaporizes upon contact with the beans. The Sivetz fluid bed roaster, which is used by some professionals but in far smaller numbers than drum roasters, has a water cooling feature built into it but the spray hits the upper inside surface of the super heated drum for only about ten seconds while the beans are flying past at a high velocity.

If you are home roasting it is preferable to aid the cooling with a small fan that blows onto the beans and do some manual agitation. I used to toss the beans back and forth between two metal colanders when I was roasting on an Alpenroast. Best of all is to learn how to cut your roast just bit short of where you want the final level to be and allow for the fact that the beans keep roasting for a minute or two after the heat is removed and they hit the cooling bin.

I was recently up at US Roaster Corp in OKC. They have several grad students working various coffee related master theisses. One doing afterburners, other roaster efficiencies, and the other working "water quenching".

Intrigued, I asked for more information. The basics of the process are...water has an very high specific heat capacity...meaning that it will absorb a lot of energy as it rises in temperature. You also have the energy associated with phase transformation (water to steam).

So, their lab roaster is a 3 kilo roaster witha lot of computer control and instrumentation....at the end of the roast they inject several cc's of water at high pressure (above the beans). Given the extreme air temperatures in the roaster (420 to 470 F), the water heats, turns to steam (most of the vapor is removed in the exhaust), and in the process absorbs a tremendous amount of energy from the air (and in turn reduces the air temperature very quickly)...stopping the roast process and beginning the process of cooling the beans during the bean dump.


I was told that this is a common process for their roasters in larger sizes (30, 60, 90, and 120 kilo roaster) in order to stop the roasting process at the end of the roaster prior to dumping the beans.

Yeah, in a Gene Cafe, probably your best bet is to dump the beans into a colander and use a fan, or onto a prechilled cookie sheet or something.

Cooling in the roaster is suboptimal, as there's all that thermal mass. Once you've done the step of cooling outside the roaster, then you can worry about speeding up the process with other means, but your bigest bang is going to be cooling externally.

I have a big rack fan attached to the bottom of a percolator basket, drawing air down through the beans. I can do a pound in about 4 minutes to ambient. Not perfect, but not bad.

Thanks for the info all. Yes, the person I heard this from worked at a larger scale roaster (doing batches of 75kg) He also mentioned the water evaporated directly, so the beans would never be really wet. Cooling down with two colanders is also what I tried, so far that seems the fastest and that is when I get the idea of cooldown with water (wouldn't wanna do it in the Gene)

Just received a lot of new green beans, will roast them first in my more conventional way, to get to know their taste. And then I will just give it a try, maybe just spraying water, so it evaporates directly. In theory this should be a fast way to cool down.

I will keep you guys posted on any progress made.

ive never seen water quenching used in specialty coffee but I have seen it used on very large roasters and i had a water quench system on my current roaster a 15k, .. i never used it and un-installed it just a couple months back.

when the roastery gets hot i rig a dryer duct hose taped to an air conditioner vent to give the cooling bin a blast of cool air .. this also works from a window unit, .. better than one would think.

happy roasting!
Mark

When I started roasting I used a spray bottle to cool the coffee. It works, but if you over do it it will ruin the batch. After ruining (they were incredibly sour) two batches in a row, I came up with using a spare dust collector as a cooler.

See:

http://www.youtube.com/watch?v=S2mRgPpIFxA

For the cooler in action. The advantages are as follows:

1. I roast outdoors. The ambient temp varies. Stopping a roast a couple minutes before it is "done" is beyond me under these circumstances. If "done" is first sign of second crack, that would mean you'd have to stop the roast a couple minutes earlier. Way too much to expect of me, anyhow.

2. It removes a variable from the coffee roasting equation, a potentially critical variable. It also removes virtually all chaff.

3. It is fool proof and since it only takes 15 seconds, it isn't horribly noisy. Less than a shop vacuum.

4. They are cheap. You can get one from Harbor Freight for less than $100 and Craigslist for even less.

5. They will easily cool two pounds of coffee at a time. I usually do one pound and 12-15 seconds later it is cool and chaff-free.

6. You could hook up a hose and use it to blow the area clean (like a leaf blower).

7. A electric leaf blower would work the same way, if you have one. They are very cheap.

I really don't understand why this hasn't caught on here -- I did a post some time ago, and I can assure you that it works very well. I really don't think there is anything better, and guessing when to end a roast is really difficult to do consistently. When i want to end the roast, it is over 10 seconds after I make the decision, not minutes after.

dan

7. A electric leaf blower would work the same way, if you have one. They are very cheap.

If you don't mind melting it. Most cheap leaf blowers have plastic impellers.

I've not seen this kind of fan before. Looks awesome. Beats the snot out of my large rack fan. Off to find one

Here is a link to the Harbor Freight dust collector. You will need to either get a colander that is the right size or rig up something to hold the one you have-- some sort of ring (like a wok ring) or even a bowl with a hole cut in the bottom. It is easy to take off that little cart. In my case, I had a different one I got free, but I also have two of the HF ones for my wood shop and they work fine.

I suspect that the leaf blower wouldn't melt, (the exposure to hot enough air to melt plastic) is really less than about 3 seconds, but you could be right. (I can put my hand in the beans three seconds after turning on the blower). But, one could easily do it the other way -- just have an arrangement that keeps the beans from blowing away. A couple colanders forming a clam shell might work.

http://www.harborfreight.com/1-hp-mini-dust-collector-94029.html

Anyhow, getting rid of variables is very helpful in doing repeatable and predictable roasts. If I had a small commercial roastery and wanted to limit myself to a few house offerings, I could figure out when to stop the roast taking into account cooling. But I experiment with lots of different beans and it's just too hard to predict for me. Plus, I normally do two batches, one after the other and its nice to get on with it.