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Looking for good info on drying phase during roasting
nixda
Hi y'all,

For refining my roasting profiles, I have started to pay more attention to the drying phase, but I have had problems finding good info. There are tidbits strewn around the Internet, but I was wondering if there is any thorough and reasonably complete discourse somewhere. Essentially, I am looking for info regarding durations and temperature ranges of the drying phase depending on bean origin (altitude), processing, hardness (if the vendor is so kind to note) and any other easily assessed parameter that is important here. With "easily assessed", I mean that I do not have special equipment to measure moisture content or density.

If it's important, I roast in a HG/BM roaster that is fairly tight (insulated RC, tight-fitting lid); I generally preheat my RC to around 230°C/450°F, but I am certainly open to suggestions here.

Thanks very much in advance.

Cheers!
 
oldgearhead
I've spent a few days drying coffee and many years drying corn. I think the biggest problem with coffee is when it arrives we have no idea how much moisture arrives with the bean. Therefore, we don't know how long the 'drying' phase will actually last. I have three different beans in my cupboard with three different % moisture contents, 8%, 12% and 11%.

So my first suggestion is to derive a means of determining the 'test weight' of your green coffee beans. I have a plastic cup that I measure exactly 240 grams of beans into. If the 240 grams of beans extend above the top lip of the cup I assume a low 'test weight' and a bit shorter drying time. Or in my case (fluid-bed roaster), less air injected during drying. If the beans are below the lip of the cup I assume a high 'test weight' and a longer 'drying phase' or 'more air' with a fluid-bed roaster.

Like grain, coffee beans will lose moisture rapidly when subjected to air temperatures above 100°C. Faster drying can be achieved by increasing either the temperature or the air-flow. Also, like grain, it is harder to remove moisture as the moisture % becomes smaller. This is probably a good thing because a small bit of moisture is required for the bean to roast properly...
 
freewillow
MAy answer a little too late. Discussin with a frech pro roster, his opinion is that the right time to the first change of color ( beans getting "paler') should be 5 minutes. So with experience adapt the temperature in order to get it in 5 to 6 minutes. on my Gene, I need 200°C (390°F) for 250 grams. But this cannot be translated directly to other genes and certainly not to other brands of roasters :)
 
nixda
Thanks all.

There are double-roast approaches whereby one subjects the beans to a roasting process that is then cut short before any appreciable Maiilard reaction. Later then the beans are roasted properly, faster than what one would normally do (because the beans are essentially already dry). Perhaps that will even out the effect of varying amounts of moisture in the beans, so that one could focus exclusively on roasting. As a one-pound-a-week roaster, it will take me some time to investigate this approach for myself, though.
 
freewillow
Have seen it recommended here in erope for ethiopian coffees like the yrgacheffe that is rather difficult to roast evenly. Never tied it :(
 
Lawnmowerman
Nuehaus Neotech does this if I remember correctly, but it is employed in a continuous batch setup. I had assumed that this was mainly to speed up the process.
Ben.
Bad coffee prevails when good coffee roasters stand by and do nothing.
 
ausjpatt
Does the Mailard reaction time not matter? There is a lot of talk about drying and first crack but what about the middle? Just have been curious about this for a while but have yet to experiment. Has anyone here?
 
billsey
ausjpatt wrote:

Does the Mailard reaction time not matter? There is a lot of talk about drying and first crack but what about the middle? Just have been curious about this for a while but have yet to experiment. Has anyone here?


The Mailard reaction time makes a huge difference in coffee taste. Check out Rob Hoos' book for more info. I'm usually trying to stretch that section to emphasize the fruit notes on my batches.
 
ChicagoJohn
billsey wrote:

ausjpatt wrote:

Does the Mailard reaction time not matter? There is a lot of talk about drying and first crack but what about the middle? Just have been curious about this for a while but have yet to experiment. Has anyone here?


The Mailard reaction time makes a huge difference in coffee taste. Check out Rob Hoos' book for more info. I'm usually trying to stretch that section to emphasize the fruit notes on my batches.


How would the maillard reaction time be related to the concept of "development" that people like Scott Rao say is important in dictums such as that 1C be 75 - 80% of total roast time? Sort of a "browning" effect as in other culinary pursuits like onions or steaks?
So many beans; so little time....
 
Ringo
I believe the time between 340F and 1st crack is when the fruits (blueberry) and sugars develop. I think when raw sugar is browned it caramelizes and we can taste sweet. If you go too long the caramel is burnt. So for me when I do not get the fruit or sweetness I believe I was in mallard too long or not long enough. I believe after 1st crack you balance the complexity of the roast to the acid. Too short and acid will overpower and you will not have layers of flavors. Get it right acid will be balanced with layers of complex flavors. Get it long acid is dead or flat and char flavor replaces the complexity.
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
 
ChicagoJohn
Ringo wrote:

I believe the time between 340F and 1st crack is when the fruits (blueberry) and sugars develop. I think when raw sugar is browned it caramelizes and we can taste sweet. If you go too long the caramel is burnt. So for me when I do not get the fruit or sweetness I believe I was in mallard too long or not long enough. I believe after 1st crack you balance the complexity of the roast to the acid. Too short and acid will overpower and you will not have layers of flavors. Get it right acid will be balanced with layers of complex flavors. Get it long acid is dead or flat and char flavor replaces the complexity.


Great! I'll print this out and work with it. I've been reading a lot and haven't seen such a succinct summary of the processes. I have not been paying attention to the time before 1C, in Centigrade 170 - 195C. I can see where aromatic aldehydes and ketones could be created in that region. I will now incorporate that time-temperature variable into future experiments. Thanks!!!
Edited by ChicagoJohn on 08/13/2015 3:41 AM
So many beans; so little time....
 
billsey
ChicagoJohn wrote:
How would the maillard reaction time be related to the concept of "development" that people like Scott Rao say is important in dictums such as that 1C be 75 - 80% of total roast time? Sort of a "browning" effect as in other culinary pursuits like onions or steaks?

It's a bit confusing, since the Maillard reaction continues after 1C. The roast segment I believe we're talking about is the time between the end of drying (first changes to scent, grassy smell indicate Maillard has started) and the start of first crack. Shortening or lengthening this period affects final flavor unless you take it past Maillard and into carbonization. The light volatiles are formed during this time, fruit and nut flavors being a portion of the effects, sugars another. According to Rob you can use the characteristics of this period to choose the final result when trying to match a flavor profile to a different roast. What Scott is talking about as the development phase is also part of the Maillard reaction, but from the start of 1C to the end of 2C. What primarily happening during the late Maillard reaction period is conversion of sugars by caramelization, giving the deeper notes like chocolate. Going past Maillard reaction is where the final carbonization happens, killing off all the flavor and leaving just *$ behind. :)
 
Ringo
The way I look at it is it a guide. The best way to improve your roasting is to do two roast at the same time and change one thing. Maybe do one with a 2 1/2 min development time and one with 3 min development time, drink them both and find out what you like. Next maybe change the time from 340f to 1 st crack. I was in a lab one time and watched the them develop a profile for a commercial roaster. They did 6 different roast and cupped them side beside then they did round two. At 12 roast profile they had what they wanted but said twice a day they would cup the coffee coming of the big roaster with the operator. We can not do that many different profiles as home roasters but if we do two or three we can get very good. Another thing I do is go to sweet Maria's and buy a coffee they roast and buy some roasted and green. I then roaster it and cup the two together to see how I am doing.
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
 
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