To the original poster: I have written this as a general guide to a new user who would attempt to use this type of roaster in a home roasting setting. I have therefore assumed that the desired roast level is not "cupping level," rather to a level that someone would use who wanted to consume the coffee, not cup it. I did this because this is a home coffee user website and most people who will read this post are home roasters and not in the business of cupping coffee. The OP may therefore find combining what I've written below with what Boot wrote in his article to be a reasonable fit to his needs.
My sample roaster, which I extensively hacked, undoubtedly has a lot of similarity in its behavior to your Probat. I haven't seen your exact roaster so it is possible that some of what I'm commenting on is already included in your equipment.
I used my Probat-Burns knockoff 1lb roaster for 6 or 7 years, and will soon replace it with a self contained Diedrich 1kg roaster. I can try to give you a few pointers that I learned over time that might be of some use to you.
The Boot article which Jim references has some good points however it is addressed to people who are using sample roasters as they were intended to be used -- e.g. for roasting samples of coffee to be used in cupping. If this is not your intended use, you are going to be roasting darker and you are really most interested in profiling your roasts so that your roasted coffee meets your intended use(s). Of course, that is not what these roasters were designed to do, so you are going to have to beat that beast into submission
In order to get consistent results you will best be served by integrating an electronic stopwatch or timer plus some thermometry into your roasting process. The stopwatch will tell you if your roast is within reasonable time-temperature-roasting event parameters, and your thermometry will enable you to gain consistency once you have arrived at a general roast profile that suits you. Observing the beans as they roast will help also, so some good lighting on the swirling beans would be a nice thing to have.
Assuming that your sample roaster has a large tryer hole at the entry, you could fashion a stand of some sort with a rigid thermocouple that you can insert into the swirling beans once you have charged the roaster with beans. Make sure to insert this the same length each time to insure consistent measurements. Be sure to examine the roaster drum as it revolves so you are sure that your probe won't get chewed up by the drum's vanes. Get an electronic thermometer (thermocouple reader) that gives good and consistent readings. I have seen such products sold for under $20, but if you want a nice one consider getting one from Fluke or Omega that has datalogging capability.
To make the whole learning process easier, use a consistent charge weight. I don't know what is the maximum charge weight of your roaster, but I'd assume it is no more than a pound. I"d suggest taking the maximum charge weight you can use that divides evenly into your unit weight of purchase of green beans, probably a pound. So you could use a pound, if the roaster will accept it, or half a pound, for example. This will cut down on your green coffee waste in that you won't be left with 2oz or 4oz or whatever at the end of a bag of green coffee. Once you pick your charge weight, stick with it; why introduce needless variables into your roasting procedure, especially when you are learning?
Find a charge temperature that you can use that won't scorch or otherwise damage your green beans, then stick with it. I use 350F on my probe located in the middle of my drum, however your drum might need a different temperature. This temperature should be close to as high as it can be without inflicting bean damage. Once charged, use a "moderate" flame height or temperature for the first 3-4 minutes, then increase the input temperature or flame height so that you can hit the onset of first crack by about the 8 or 9 minute point. A minute or so before first crack will be reached you should cut back your heat source so that you do not enter first crack with too much energy, which will prevent you from getting an adequate interval between the onset of first crack and the end of your roast. For espresso I would suggest shooting for an interval of about 4, no more than 5 (or less than 4) minutes between the start of 1st crack and the end of your roast. As to the roast level, this will depend on the bean however I would, again for espresso, be looking at roast levels from a few degrees shy of the onset of 2nd crack to (perhaps) as much as 15 seconds or so into rolling second crack. I almost never roast into 2nd crack personally, however there are some beans that "prefer" that.
Initially I would concentrate on the cracks and trying to correlate them with your thermometry observations. Once you have a general idea of how these things correlate and how you can reach my suggested general time-roast event parameters (which are not really mine, they are stolen for the suggestions of others to me over the years) you can start to use the thermometry to help you gain consistency. Over time you will likely find that the thermometry is more useful than any observations you might make of the beans
while they roast, since on-the-fly changes in roasting inputs can be very difficult without thermometry that you
trust.Finally, I liked Boot's suggestion of having a measure of input gas flow to the heat source. I incorporated that into my own roaster 6 years ago at the suggestion of a professional roaster, and I have found it to be invaluable. My new Diedrich will include this feature as a stock item.
Good luck.
ken
by coffee4476 on Tue Jan 11, 2011 9:06 pm 
