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Roast profiles -- general principles?
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Discussions > Coffee > Home Roast > Roast profiles...  
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Bear_B
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Posted Wed May 14, 2008, 10:45pm
Subject: Roast profiles -- general principles?
 

Hi all,

This is my first post, though I've been quietly reading the forum for a while.  I started roasting coffee in an iRoast 2 in late January of this year and have been having a wonderful time doing it!  Recently, though, I've run up against a question that I haven't seen answered in any comprehensive way anywhere, and I'm hoping that someone here can point me in the right direction.

My starting point is two batches of Sumatra Classic Mandheling that I roasted a couple of hours apart using different roast profiles -- the first one was 2 min @ 340, 3@390, 6@450, and the second was more extended -- 3@340, 2@355, 2@365, 2@375, 6@450.  In both cases I hoped to get to a good full city roast right after the jump to 450, and to hit cooldown at that point, which is what I did.  So I ended up with two more or less identical batches, same bean, same roast, etc., except for the roast profiles.

But the coffees in the cup the next day were strikingly different.  The shorter roast was brighter and surprisingly acidic for a Sumatra, while the longer roast was earthy, rich, a bit of chocolate and pepper, and barely a hint of acidity -- classic Sumatra flavor.

I experimented with a couple of other beans and discovered that the first profile in general tends to produce a brighter cup than the second.  But there are, potentially, quite a few reasons why that might be the case:

  • shorter ramp-up to first crack
  • steeper roast profile in general
  • less time between first and second crack
  • faster rate of temperature increase between first and second crack
  • temperature never leveling out
  • etc., etc.

I don't do a lot of roasting, just 2-3 batches a week for my own consumption, so it would take me a very long time to experiment with all the possibilities, and it's also very hard to change some of these things (e.g. time between 1st and 2nd) without changing others (rate of temp increase between 1st and 2nd).

So rather than speculate or drive myself crazy, I thought I should come here and ask whether anyone knows of a good resource on general principles of roast profiles.  I have seen a few posts in these forums with links to articles etc., but for the most part those tend to have just a couple of pages and make points like, it's important to extend the time between first and second crack.  That's good to know, but I'd also like to know why.  Does it allow more caramelization?  Does it preserve the internal structure of the bean and therefore (fill in the blank)?  Does it have some effect on the Maillard reaction?  Enquiring minds want to know!!

My ideal publication would be an article-length discussion of roast profiles, detailing how and why a change in one part of a roast profile translates into a change in the character of the resulting roasted coffee, for a wide range of different parts of the roast profile.  If such a thing exists and you've seen it, please let me know where it is!  If not, but something reasonably similar does, I'd appreciate being pointed toward that too.

Thanks in advance!
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PJK
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Posted Thu May 15, 2008, 12:41am
Subject: Re: Roast profiles -- general principles?
 

Hi Bear,

Welcome to the forum.

Your experience sounds about right to me.  Food chemistry (or any chemistry for that matter) is not my strength so all the whys are a mystery to me.

If you haven't seen it yet, Ken David's book is a good place to start. I think the title is Home roasting - the romance and revival or something like that.  It is a bit dated and may have less theory than what you are seeking but I think it is sort of a first book for home roasters.

Phil

 
Philip J. Keleshian
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Bear_B
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Posted Thu May 15, 2008, 8:31am
Subject: Re: Roast profiles -- general principles?
 

PJK Said:

If you haven't seen it yet, Ken David's book is a good place to start. I think the title is Home roasting - the romance and revival or something like that.  It is a bit dated and may have less theory than what you are seeking but I think it is sort of a first book for home roasters.

Posted May 15, 2008 link

Hi Phil, and thanks.  David's book is nice, I agree; it was my bedtime reading for a while.  :-)  But although it's really impressive as far as breadth is concerned (w/ info for example on how to roast coffee in everything from a skillet to a microwave), on the specific question of roast profiles there's not a lot.  His recommended format for roast notes at the end just has time and temperature of roast, period.  He doesn't delve into varying the temp during the roast.
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Frost
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Posted Fri May 16, 2008, 9:40am
Subject: Re: Roast profiles -- general principles?
 

Welcome to Coffeegeek Bear, and thanks for asking a great question! I am always looking for more information and education in this area. I'm a few years short of experience in compiling my self-education and experimental results on the subject. I've already roasted 20+ lbs (thats 60+ batches for me!) of Idido Misty Valley since last October. Enough experiment with a single bean will really help you sort all this out and learn about what YOU like and don't like in your cup.  

...Anyway here's the best recommended reading I've found on the subject so far. ALWAYS looking for more info if anyone out there has references. THANKS for all the help!

Roasting 101, read these articles on 'Ruling the Roast' by Boot:

http://www.bootcoffee.com/articles.html


Ken Fox wrote an excellent post on HB about his roasting experience:

Click Here (www.home-barista.com)

'Egholm' asked a similiar question a while back, so I spilled my beans in a couple of rambling posts in this thread. Not too much has changed since then for me. (a couple things on ramping through first crack.) Also Egholm uses an Iroast so his experience may be of help too:

"How does the optimal temperature profile look like?"


For starts I suggest to try and get a thermometer in the beans, pay attention the the various roast stages and how they affect the cup: drying, browning, first crack, time between cracks (...or end of roast), second crack. etc.  Keep track of times for start of first, end of roast, start of second. At least these events are somewhat 'universal' indicators of bean state across different roasters.
Keep in mind too the wide variety of taste preferences: I never roast into second crack for my espresso.

Searching and reading the posts here and at HB (such key words as 'profile') will turn up more good info. I hope we can come up with more information on this important subject.
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Bear_B
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Bear_B
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Posted Fri May 16, 2008, 10:04am
Subject: Re: Roast profiles -- general principles?
 

Frost Said:

Welcome to Coffeegeek Bear, and thanks for asking a great question! I am always looking for more information and education in this area. I'm a few years short of experience in compiling my self-education and experimental results on the subject. I've already roasted 20+ lbs (thats 60+ batches for me!) of Idido Misty Valley since last October. Enough experiment with a single bean will really help you sort all this out and learn about what YOU like and don't like in your cup.  

...Anyway here's the best recommended reading I've found on the subject so far. ...

For starts I suggest to try and get a thermometer in the beans, pay attention the the various roast stages and how they affect the cup: drying, browning, first crack, time between cracks (...or end of roast), second crack. etc.  Keep track of times for start of first, end of roast, start of second. At least these events are somewhat 'universal' indicators of bean state across different roasters.
Keep in mind too the wide variety of taste preferences: I never roast into second crack for my espresso.

Searching and reading the posts here and at HB (such key words as 'profile') will turn up more good info. I hope we can come up with more information on this important subject.

Posted May 16, 2008 link

Wow!  Thanks, Gary -- this ought to keep me out of trouble for a while....

I've plumbed the forums a fair bit and seen many of these posts; in fact, they've gotten me to where I am -- keeping track of the timing of first crack, charting temperatures, etc., etc.  (I don't have a thermometer in the actual bean mass, but there's an onboard thermometer in the iRoast 2.  That said, it's a big fat liar sometimes -- it reflects air temp, not bean temp, obviously, and with some beans, like a Sumatra, I get first and second crack at impossibly low temperatures.  My guess is that the lack of chaff is producing artificially low temp readings for these beans because it creates more of a differential between the temp near the heating element and the temp in the chamber more generally... but that's purely speculative.)

Anyway, part of the reason I posted this question is that it seems to be one that's kind of answered tangentially here and there, in response to related questions, but one that hasn't been asked squarely before.  And it seems like there must be good collective wisdom out there on it -- a suspicion vindicated by your reply.  :-)
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1or2lumps
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Posted Wed May 28, 2008, 10:15pm
Subject: Re: Roast profiles -- general principles?
 

Have you checked out the back issues of Roast magazine?  The one issue I have from the Seattle Coffee Fest doesn't have any specific info about roast profiles, but maybe some of the older issues do.  Let us know if you discover anything.

Michael
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Frost
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Posted Thu May 29, 2008, 9:35am
Subject: Re: Roast profiles -- general principles?
 

Here's another suggestion for good information on the subject: Do a search of posts by Jim Schulman here on Coffeegeek in the Home Roast forum.  It may take a few days to sort through to the relevant (profile specific)posts and put together the pieces, but well worth the effort.  A special thanks to Jim for all that!
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Bear_B
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Bear_B
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Posted Thu May 29, 2008, 9:59am
Subject: Re: Roast profiles -- general principles?
 

1or2lumps Said:

Have you checked out the back issues of Roast magazine?  The one issue I have from the Seattle Coffee Fest doesn't have any specific info about roast profiles, but maybe some of the older issues do.  Let us know if you discover anything.

Michael

Posted May 28, 2008 link

I haven't done a comprehensive search of them... but the ones I've seen haven't had anything directly to the point.  They've got a good section on the science of roasting in recent issues, which I hope will address this, but so far I haven't seen it.
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Bear_B
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Bear_B
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Posted Thu May 29, 2008, 10:10am
Subject: Re: Roast profiles -- general principles?
 

Frost Said:

Here's another suggestion for good information on the subject: Do a search of posts by Jim Schulman here on Coffeegeek in the Home Roast forum.  It may take a few days to sort through to the relevant (profile specific)posts and put together the pieces, but well worth the effort.  A special thanks to Jim for all that!

Posted May 29, 2008 link

Indeed -- Jim's posts and Tom's tip sheet for the iRoast were among my main starting points.  I haven't done a comprehensive search, but perhaps one is in order!
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Bear_B
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Bear_B
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Posted Tue Jun 17, 2008, 9:19pm
Subject: Re: Roast profiles -- general principles?
 

Hi folks,

I thought I'd post an intermediate progress report on this topic, just to stimulate discussion a bit.  I've had a busy month, so I haven't had time to do much reading up beyond the suggested links yet; mostly I've just been able to experiment, mainly with Guatemalan Huehuetenango and Sumatra Classic Mandheling beans from Sweet Maria's.  Based on those experiments and on feedback above and elsewhere in the forums, I've come to three very tentative working hypotheses.

Hypothesis #1:  A steeper roast curve -- i.e., a faster buildup of heat -- produces higher levels of sourness or acidity.

I'm not sure why this is the case.  My guess would be that the interior of the bean isn't roasted to the same temperature as the exterior, so it retains a bit of the acidity that's burned off with a slower ramp-up.  This can be a plus with some coffees (in moderation, I think it benefits the Ethiopian Organic Misty Valley that I've roasted a few times), or a minus with others (the Sumatra doesn't really seem to like it at all).

Hypothesis #2:  Lengthening the duration between first and second crack draws out the coffee's varietal notes.

I can't take credit for this one, since everyone here told me that it was true!!  I am completely at a loss to explain why this is the case, though, but the evidence from the cup seems difficult to refute.  The Guatemala produces nice milk chocolate and nut tones, and the Sumatra gives good earthy flavors and a bit of pepper and dark chocolate... but not when the temps go shooting through the roof right away.

Very tentative hypothesis #3:  Lengthening the duration between first and second crack too much actually destroys some varietal notes.

I have a very small number of roasts to support this hypothesis... but I tried a profile that got to first crack as quickly as possible and then drew out the roast from first to second as much as possible, and it seemed to kill the chocolate notes in both the Sumatra and the Guatemala.  Perhaps the additional time allows the sugars that produce those notes to caramelize too fully?  I really don't know.  But I've reverted to a slightly brisker profile as a result.

For the curious, the best profile I've found at present for the Sumatra is 3 minutes at 340, 2@355, 2@365, 2@375, and 6@450... the beans usually hit second crack about 20-30 seconds into the last stage, and depending on what side of Full City I want them, I'll hit the cool-down cycle anywhere from a bit before that happens to (my current favorite) about ten seconds after.  I'm still experimenting with the Guatemala.
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