Author Topic: I wanna build a new roaster, but ....  (Read 6934 times)

Offline stevea

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I wanna build a new roaster, but ....
« on: January 19, 2017, 06:59:58 PM »
The short story.

Can anyone comment on the 'flavor' differences between a fluid-bed vs a drum ?

I've never used a drum system, but I've tasted good stuff from some local shops.  I've used my old poppers and also an SC/TO extensively.  My opinion is that the poppers produce a brighter and cleaner flavor profile, BUT the SC/TO allows me to pull out more varietal flavor, tho' I *think* it also suffers from some smoke-deposition back onto the beans.

==  TL;DR ==

The longer story.

I'd like a personal roaster that can handle ~750 grams of greens and roast it in the SCAA 8-12 minutes.   I really dislike anything approaching 18-20 minutes (tho' that depends on profile details).

I've been intrigued by a fluid-bed design for years.  It seems so brilliant.  The air provides heat AND provides bean motion AND you can flow cool air to cool the beans rapidly.  One moving part (the blower) and one electrically heater - easily controlled.

Then when you examine the design more closely it's not so pretty.
/ There is a small range of air velocity that will jostle the beans w/o blowing them out the chute.
/ The airflow rate changes as the beans dry, and expand.
/ Air has a high heat capacity (watt-hours or joules per kg) so you lose a huge amount of energy in the exit air.
/ You can reduce the peak-power req, by increasing the heat-capacity of the roasting chamber (like a heavy iron RC) but then you can't practically us the same chamber for cooling.

I've run some numbers and something like the Sonofresco is ~10% efficient!  Poppers are even worse.  The Novoroaster might be 15-20% efficient.  OTOH Buhler makes a ~80% efficient drum system (well insulated w/ heat recovery).

To put some numbers to this, Sivietz reported that roasting beans requires 582kJoule/kg applied to the beans.  So to be able to roast my 750grams in 8 minutes I'd need to apply (582*0.75/480sec) = 900Watts to the beans.  That sounds great - but ...

If a fluid-bed is only 10% efficient I'd need a 9kW heater which means I'm wiring 40+amps of 220vac to the garage for a hobby.   Not cool.  Even at 20% efficiency that's a bung-load of power - tho' a lot more practical (you can get 5kW dryer heating elements).  Of course 9kW is ~30k BTU/hr - more practical, but flame systems are harder to control.

FWIW it takes 1kW to heat only 7.4cfm of 20C ambient air to 250C(480F) !   Blowing hot air out of a fluid-bed is a huge energy cost.  This is why drums are usually far more efficient.

--

So I *think* I have a reasonable re-design idea for improving the fluid-bed efficiency with heat exchangers on the exit air path & insulation on the 'hot parts', but it's almost impossible to estimate system final efficiency without trying it.  If I could get 50% efficiency (say 2kW in for a fast roast of 750 grams) I'd be very happy.  But building it is a big build commitment. 


Would I be happy with a fluid-bed flavor profile - or does a drum produce more caramelization products as some claim ?
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Offline peter

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Re: I wanna build a new roaster, but ....
« Reply #1 on: January 19, 2017, 07:31:14 PM »
You may want to settle the idea of what you consider a potential issue of the SC/TO's smoke deposition before you go down that long, difficult albeit possibly fun road.
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Offline ptrmorton

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Re: I wanna build a new roaster, but ....
« Reply #2 on: January 19, 2017, 08:41:29 PM »
Wow, I don't have much information to add other than I'll be interested in what becomes of this.  I've traveled a similar path with poppers and an SC/TO, but ended up with a modified Hottop.  I toyed with the idea of building a bigger drum roaster, but building a fluid bed roaster would be an interesting project to follow because of a fluid beds potential versatility in batch size. I have no experience to comment on the finished product.


Aaron will probably weigh in on this with his recent exploration/experience with fluid bed roasting and I look forward to the dialog that ensues. ;D
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Offline Joe

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Re: I wanna build a new roaster, but ....
« Reply #3 on: January 19, 2017, 10:53:18 PM »
Electrical heating sounds like a challenge but the rest of your stuff sounds awesome. Have you thought of propane or Natural gas i.e. Sonofresco style?

And regardless of anything I think you need to make this happen so we can witness this together ;D
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Offline Ascholten

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Re: I wanna build a new roaster, but ....
« Reply #4 on: January 20, 2017, 07:31:45 AM »
My Artisan uses dryer heating elements as it's heat core.  I can vary the KW input to them.  I don't know how efficient it is, and honestly, am not too concerned when it only cost me maybe a dime or so to roast 5 Lbs of coffee on electric.

I can put 7500 watts to 5 lbs and it's done in about 20 minutes.  Thinking of BTU vs efficiency makes my head hurt.  I have to do number crunching like that all day at work, no offense but I do NOT want to have to do that too at home!

I can think of ways to boost efficiency with your fluid bed shape too to be honest.  It's a trade off here and there.  If you are going to roast the same amount every time with beans that have the same lofting properties, yep you can tweak something in pretty good, but if you are going to do varying loads with varying surface frictions and lofting requirements, there will be some give and take.

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Offline stevea

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Re: I wanna build a new roaster, but ....
« Reply #5 on: January 22, 2017, 11:10:07 PM »
With a couple EE degrees on the stack, I have a natural bias toward the electrical/electronic solution.  Even at high power it's relatively cheap & accurate to control an electrical heater vs a 'burner' system.

A fired burner isn't expensive; heck you can tear the guts out of an junk-yard nat.gas water heater and have a ~40kBTU/hr (~11.7kwatt) burner and you get an on/off solenoid, electrical ignitor and a thermocouple to boot.   The headache is that to control the nat.gas supply electronically means a proportional valve + controls and ~$300+ for one stinking variable.   There are alternatives, but all involve expensive proportional valves or slamming a solenoid valve open & shut at a high rate.  Mechanical stuff just isn't as easy to control as electrons.

As I read the papers it looks like a steady inlet air temp (~250C/480F) is most of what I need - so it *might* be rational to simply adjust the burner system manually during warm-up, then tweak it.  Not pretty - I want this automated and repeatable from run to run.

Also those inexpensive burners have the wrong shape for the sort of build I'd like to do.   I want all that heat near the beans and inside a ~3-4 inch diameter tube - that calls for a custom burner I think.

Now 9kW electrical heaters (from my above example) is would be trivial in a light-industrial setting, but in a residence ....  You need 220vac, at ~41 amps and that sounds a lot like me dragging 8/2 8AWG wire ~60ft from panel to garage and hanging conduits as I go to remain w/in code.   Do-able, and the result will be easier to control - but SHEESH all this for 750grams of greens !  Really ?   It just 'smells' like something is wrong with the design !


My Artisan uses dryer heating elements as it's heat core.  I can vary the KW input to them.  I don't know how efficient it is, and honestly, am not too concerned when it only cost me maybe a dime or so to roast 5 Lbs of coffee on electric.

At typical US rates (~$0.12/kw-hr) you're spending ~30 cents for 20 minutes at 7.5kW.  Totally trivial amount cost - we agree.  As I mentioned above - efficiency is a concern NOT b/c of energy cost, but b/c it's a bloody mess trying to get enough energy into enough beans in a reasonably small amount of time. 

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I can put 7500 watts to 5 lbs and it's done in about 20 minutes.  Thinking of BTU vs efficiency makes my head hurt.  I have to do number crunching like that all day at work, no offense but I do NOT want to have to do that too at home!

Heh - I enjoy the quantitative aspect of issues - it's the engineer in me.  So if you'll forgive me, my friend,

7.5kW * 20min[1200sec] = 9 megaJoules !
5lbs of greens is 2.27kg, and Sivetz says you need 582kJ/kg so your means absorbed ~
2.27kg*583 kJ/kg = 1.319 MJ

Efficiency = (1.319 MJ /  9MJ) * 100% = 14.65% efficiency.

Frankly that's a good number and handily beats the Sonofresco & is in the same ball-park as the Novoroaster.


The reason why I find it so troubling is that I don't want a 20 minute roast.  My design goal is for an 8 minute roast, and I'll happily add a few minutes as I choose a profile - not b/c the system is underpowered.


Put another way - *IF* your Artisan6 efficiency was constant and you could do a 5lb roast in 20min, then to get an 8 minute roast your system would only handle [ 5lb * (8min/20min)=] 2lbs. (~900 grams) !  In reality the efficiency will drop with smaller loads, and then my 10% efficient, ~9kW  applied to 750grams for 8 minutes  looks realistic.

--
We would both be a lot happier if we could get the fluid/spouted-bed system efficiency up - whether that means faster roasting options or bigger loads.  I believe the ideas I've outlined might get the fluid-bed efficiency up toward 50% - but only a build+experiment can tell.

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I can think of ways to boost efficiency with your fluid bed shape too to be honest.

Can you elaborate on that ? The data on coffee fluid beds is pretty sparse, but it looks like a bed depth ~4 inches of greens is about optimal, and above 6 inches lofting the beans become problematic.   You'd think a deeper bed would gain some heat transfer advantages, but ... it's sadly the fact that fluid-bed requires a specific range of air flow to loft beans, and that may not be the optimal flow for heating the beans [it's an over constrained design].

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If you are going to roast the same amount every time with beans that have the same lofting properties, yep you can tweak something in pretty good, but if you are going to do varying loads with varying surface frictions and lofting requirements, there will be some give and take.

Yes, that's a headache and requires that we build some excess capacity into the system.   I prefer to roast those weird little mis-shapen harrar beans, but also some nice big uniform S.American beans.   I once had a bag of some absolutely huge Mexican beans (but the flavor was woody and not good)- then again peaberry won't have the same lofting characteristics either.  A "typical" bean has a terminal velocity ~15+ meter/sec, but only drops to ~13m/s once roaster (lighter & bigger).  Thats for 20C air, but the hot air is considerable less dense and has to flow at a higher rate to get the same lift.  Anyway the one paper w/ specifics claims 5.5m/s air velocity will spout beans (w/o pinning then to the upper screen).


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Offline stevea

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Re: I wanna build a new roaster, but ....
« Reply #6 on: January 23, 2017, 03:23:36 AM »
You may want to settle the idea of what you consider a potential issue of the SC/TO's smoke deposition before you go down that long, difficult albeit possibly fun road.

I'm completely convinced that a popper vs an SCTO produce some different characteristic flavors regardless of profile.
The poppers seem very 'clean' early on while the SC/TO produces some sort of tongue tingling (tarry?) hot flavor that somewhat dissipates in a day or two.  The poppers are decidedly more acidic, and I suspect that's b/c the bean can remain a little 'raw' in the interior - esp with a too-small too-fast roast.

I've read subjective reports suggesting that there is more caramelization in drums than fluid beds, and that could match my experience as well.   Any comments on that ?

Where is Mr.Huky ?
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Offline Ascholten

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Re: I wanna build a new roaster, but ....
« Reply #7 on: January 23, 2017, 02:48:49 PM »
Steve, it doesn't have to take 20 minutes.  I typically have mine done in 12, i was talking pour to pour time.
Loft time IS a big factor.  if you have a small pile, the air along with the heat is boom here and gone, too fast, you end up actually having to pump more watts into a smaller batch to get it going than you'd have to do with a larger  batch.  My Artisan 6 is rated for 5 lbs of coffee, Ive don'e 8 in it.  Typically Ill do 2 lbs at 5500 watts, fiddling with it a bit to control my temp ramp.  Now I can do 8 oz with it, but damned near have to use the same wattage to get the heat into the beans properly because that small a batch has too narrow a bed.  1 Lb I can do with 4000 watts give or take if I want.

Loft is an issue for sure, one thing I was contemplating for mine for smaller roasts was a narrow possibly a bit taller roast funnel chamber.  That way the air is constrained and the beans are 'tighter' so the column is thicker so more there to absorb the heat as the air passes.  The heat density is higher. This is kind of what i meant by shape makes a difference.  With a tall enough chamber, and no im not talking 4 foot roast chamber though that would be very interesting, you would have enough move room to keep the beans well agitated and enough room to let the heat get to them.  One thing I notice if you have the air going a  bit too hard is the bean mass starts to 'wuffle' for lack of a better turn,  the entire mass while agitating, bounces up and down kind of making a woof woof woof sound.  Turn the loft down cures that.  Another reason a bit taller heat chamber is nice is because there is less of a chance of errant beans being thrown out, not to mention if you do have the air going a bit fast and they are really moving around, its more time to interact to suck up the heat.

Good luck with your roaster.

Aaron

P.S  was goofing around trying to roast one bean with my 20 watt laser one day.  Didn't work too well hehe.
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Offline stevea

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Re: I wanna build a new roaster, but ....
« Reply #8 on: January 26, 2017, 03:22:20 AM »
Steve, it doesn't have to take 20 minutes.  I typically have mine done in 12,

Yeah - I understand, and that bumps your system efficiency a little higher, but we still talking <20%-ish.
Also I recognize that batches simply do not scale in - particularly in a fluid/spouted bed roaster.

FWIW there are some claims that a Huky can't do a fast-roast and will scorch beans.

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Loft is an issue for sure, one thing I was contemplating for mine for smaller roasts was a narrow possibly a bit taller roast funnel chamber
From all I've read and seen that makes sense.  You want the bean-bed depth to be fairly constant and in a narrow range (75-150mm in one paper).  You might also play with switching the 'throat' diameter to adjust the air velocity.

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One thing I notice if you have the air going a  bit too hard is the bean mass starts to 'wuffle' for lack of a better turn,  the entire mass while agitating, bounces up and down kind of making a woof woof woof sound.

They call that 'slugging' in the Kunii-Levelspiel papers.   You are getting  big air bubbles under the beans.

Even the Artisan 2.5 uses 5.2kW (one dryer heating element), whichi is still a lot of power.

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P.S  was goofing around trying to roast one bean with my 20 watt laser one day.  Didn't work too well hehe.

Isn't some roaster using halogen lights as the heat source ?  I seem to vaguely recall that. 

The Aillio Bullet R1 uses an induction heater to directly heat the drum (wish there were better pix of that).  So they claim they can roast 1kg with a 1500W power source.  This actually makes a lot of sense as they are only heating the drum (I assume) so they aren't wasting a LOT of power heating waste-air and hardware as in the Huky.

The story remains the same - if you want to roast a reasonable amount of beans in a reasonable amount of time you either need an UNreasonable amount of power, OR ELSE you need efficiency.

--

My question remains unanswered.   Does anyone feel that drum-roast coffee tastes different from fluid-bed roast ?


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Offline Ascholten

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Re: I wanna build a new roaster, but ....
« Reply #9 on: January 26, 2017, 12:50:48 PM »
Which is better, ford or chevy?

That is the type of question you are posing there.  I grew up on an I roast and have had wonderful roasts on it, then switched to a Behmor and have pulled some awesome roasts out of that too,  now back to CFB roasters and got this Excelso I am selling, gave some away and have people ordering stupid amounts of roasted beans.. so am taking that to be, yep I did good on a bed roaster.

Two points I wish to make and I'll shut up.

#1  YOUR better may not be MY better,  define what 'better' is? Get people to all agree.
Yes I will concede you asked if they taste different, but two drum roasters can provide different tastes.  Is different better?  We are searching for better generally, not necessarily just different.  To answer your question, yes they can taste different, the method is different to the same overall process,  but is that good or bad is entirely on you.

#2 The whole, air bed sucks, drum .. GOOD!! mentality, I snicker at.   Learn how to use your machine.  Again, different is not always better.  Just because you bought a Ferrari does not mean you know how to drive one.  People who want to complain that they can't get this or that out of one type over another really need to learn how to use the machine better.  That is just my unqualified opinion though.

I have oh god, I want to say 12 or so years roasting experience now, using both fluid bed and drum roasting, along with some methods im not sure what you should call it, and can honestly say I have never had anyone tell me, this coffee sucks, you should have drum roasted it / air roasted it etc.

heat gun / dog bowl,   converted popcorn stirrer machine... not drum, not air, do those taste different too?      hehe.

Aaron
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Offline stevea

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Re: I wanna build a new roaster, but ....
« Reply #10 on: January 27, 2017, 12:09:11 AM »
Which is better, ford or chevy?

That is the type of question you are posing there.

No,  "better" is totally subjective.

I'm asking how ppl perceive that a Ford differs from a Chevy - the sort of information any reasonable person would ask before plunking down $30k for a car or $5k for a roaster.  There are magazines and websites devoted to comparing car parameters, power, handling, weight, acceleration, headroom, trunk size, noise level.  Zilch for roasters (a smaller market for sure).

I think there is a very clear difference in flavor when I roast the same beans in a popper vs an SCTO and I've tried to describe it above.   I was hoping someone could make a similar comparison for drum vs fluid-bed.  OF COURSE the specifics matter.  If I had a power control/variac on the popper I might get better results - but that doesn't completely explain the diff.

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I grew up on an I roast and have had wonderful roasts on it, then switched to a Behmor and have pulled some awesome roasts out of that too,  now back to CFB roasters and got this Excelso I am selling, gave some away and have people ordering stupid amounts of roasted beans.. so am taking that to be, yep I did good on a bed roaster.

I take that as fluid-bed/drum/fluid bed.  So my question is - do you perceive a difference in same/similar coffee between the Behmor vs Artisan - for example.  Is one brighter/cleaner vs sweeter or ... or whatever ?


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#1  YOUR better may not be MY better,  define what 'better' is?
Which is why I never asked for better/worse.

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Yes I will concede you asked if they taste different, but two drum roasters can provide different tastes.

What I'm trying to decide is if there is any flavor diff attributable to heating method -  drum vs fluid bed.  If I owned comparable hardware i'd do say 5-10 roasts of same beans in both - trying for a similar profile - and compare the results.   A little experience on the hardware + some comparable *might* tell me what I need to know.

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#2 The whole, air bed sucks, drum .. GOOD!! mentality, I snicker at.


You didn't hear that from me.  OTOH there are rational reasons to think that MAYBE fluid-beds might dry the beans more and produce less maillard products.  If you study how that make dark malts for beer they use an enclosed box to trap more moisture and slow the drying while they heat.


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I have oh god, I want to say 12 or so years roasting experience now, using both fluid bed and drum roasting, along with some methods im not sure what you should call it, and can honestly say I have never had anyone tell me, this coffee sucks, you should have drum roasted it / air roasted it etc.

Well I've got a year or two on you then ...  but this is never about "better".  "Better" is a personal, normative judgement, whereas 'more acidic', or 'less sweet' or 'flatter' or 'tarry' is an attempt to describe what you are tasting.  Some ppl (a lot actually) think that Starbucks over-roasted  or MacDonalds flat-cocoa baked beans are "better" , that sort of judgment isn't what I am looking for.

It's also not about "this sux", coffee; I assume most ppl here w/ a little experience could produce a genuinely good roast on a campfire pan.  I'd like to hear an opinion of flavor differences characteristic of fluid-bed vs drum system from someone w/ experience on both.

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heat gun / dog bowl,   converted popcorn stirrer machine... not drum, not air, do those taste different too?

Yes I suspect there is a diff there, tho' I've never used a dog bowl.

My speculation is that the flavors I get on my SC/TO (the converted stir-crazy+toaster oven) are partly due to smoke-deposition on the beans and the fraction of chaff that hits the heating element & burns as air re-circulation.  I think that is why an air-popper (and likely a dogbowl) do(should) give a cleaner flavor.  You aren't re-circulating the smoke-y air onto the beans nor burning chaff.  Something like a Huky w/ an ignition burner below might have a lot more burnt-chaff flavor than your fluid-bed if chaff drops onto it - or so I would speculate.

OTOH It's likely a fair-bit easier to get caramel/maillard flavors & aroma with more moisture, and that suspicion would put the SC/TO & drums at the top of the list, and fluid-bed at the bottom.

I can think of other 'systemic' reasons why there might be flavor diffs, but only some experience on both systems could tell - I'm looking for someone w/ experience on drums & fluid-bed to compare & differentiate the roasts - and not give judgement of preference.
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Offline Ascholten

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Re: I wanna build a new roaster, but ....
« Reply #11 on: January 27, 2017, 01:32:31 PM »
I have heard some people say that fluid bed is brighter.  You even said something to the affect of drying .vs. malty etc,  slow the roast down a bit then.  You can generally control that aspect fairly well (unless it's just a bright coffee) with the method most the time.

When I did my sulawesi I did not have brightness problems at all.  You are worried about drying the beans more?  You are heating them up to 425 degrees or so.. yer gonna dry them out bud.  If you are saying one dries them faster than the other, again, slow down your roast / heat input.

I havent compared the two methods really.  I may if I get time, do a run through my behmore of say 12 oz and run in the artisan and see if I can tell any differences in them.  Im sure there will be as the methods are way different but I'll see.      Sorry bud I am not roasting 10 batches though.

Aaron
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Offline stevea

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Re: I wanna build a new roaster, but ....
« Reply #12 on: January 27, 2017, 11:24:34 PM »
Thanks sincerely for the comment Aaron - it's appreciated.

I have heard some people say that fluid bed is brighter.  You even said something to the affect of drying .vs. malty etc,  slow the roast down a bit then.  You can generally control that aspect fairly well (unless it's just a bright coffee) with the method most the time.


'K - brighter but controllable - that makes sense.
'Malt' was a reference to how they treat brewers malt (sprouted barley) for caramelization by not over-drying.



<TL;DR>   The inevitable long-winded circumlocution

In a former decade I was very involved with brewing & the beer industry & I happen to be a science-geek as well.  So at one point I did some studies of the Maillard reaction after reading lots of papers on the topic.  As a result I find nearly all of the popular article reference to the Maillard reaction annoyingly inaccurate. 

Louis Maillard was a very imaginative French chemist circa 1912 who described a hypothetical (and still unproven) set of reactions that could leave to a SPECIFIC type of "browning reaction".  But not all browning is Maillard browning.  Most of the oompa loompa's writing, even very detailed descriptions, fail to understand basics.

Maillard browning happens between simple sugars & di-saccharides (only reducing saccharides with a terminal carboxyl end, NOT sucrose)  and free amino acids (usually from proteins), REQUIRES water for the strecker degradation (but too much water acn limit temps).  The rate is very dependent on the temperature (mostly from ~80C to 140C (where even water vapor is practically lost), depends greatly on the pH as well (generally higher rates of formation at higher pH, not always), and the specific amino acids & sugars.  Maillard's description addresses broad classes of thousands of potential chemicals - not specific reactions.

Caramelization reaction is between sugars and the amines (NH2's - NOT  amino acids).  It has similarity to one of the early steps of Maillard (the amine nitrogen attach to the carbonyl groups) - but cannot produce the same range of flavors - just a basic one-dimensional flavor range, and lots of brown color.  Commercially they produce caramels by heating sugars with a little ammonia - no amino acids.   This results in, at first, the sort of sweet, hot compounds we think of as caramel candy, but then as the reactions progress all sweetness is lost and you just end up with a soluble coloring agent used in cola &  Canadian 'whisky' (I use quotes to avoid leaving the impression this stuff is real whisk[e]y)  as well as other foods.  Some amount of caramel is produced in any Maillard reaction, but caramelization is NOT Maillard.

Fatty acids (often produced by heating triglycerides) can react w/ free amino acids, create a similar carbonyl nitrogen substitution, produce brown colors and a great range of flavor - but fat+amino reactions are NOT Maillard.

Then there is enzymatic browning - the common example is when the phenolic compounds in a sliced apple oxidize and brown in when exposed to air & phenol-oxidase enzyme.  Enzymatic browning is NOT Maillard..

Also there is another sort of browning reaction - carbonization.  If you simple heat starch or sugar w/o any amine or aminos at all - this initially browns, then this leads to a more rapid extension we call 'charring' somewhere above 400F..  Basically you wreck the hydrogen bonds in the starch and produce 'charcoal'.  Again - NOT MAILLARD AT ALL.

Maillard is about sugar+amino acid reaction, not fat+amino,  not sugar+simple-amine caramelization, not enzymatic browning, not starch browning.  Not all browning is Maillard..

So blogs like this ....
http://www.chefsticks.com/searing-maillard-reaction-and-deglazing/
andpop-science sites like this ...
http://www.scienceofcooking.com/maillard_reaction.htm
are"mostly wrong".  . The color & fond of seared meat is a chemical reaction, and there are loads of amino acids available in the meat surface, but the only reducing saccharides available are from the tiny amount of glycogen locked tightly in the muscle cells, vastly reduced after slaughter and certainly not significantly released by cooking.   To put this in perspective, a 1lb steak has about as much sugars & Maillard product potential as one 1/30th of a tsp of sugar, and most of that is locked up inside the meat - not at the surface.  Yes there is a LITTLE Maillard product formation, but most frond is from fat+amino acid reactions.   Shaking on some cornstarch + baking soda (for higher pH) on your roast before searing makes a profound difference b/c it's dramatically 'upping' Maillard products to the fat+amino browning.

Taking it home - coffee beans have water, starch, oils and proteins, so we expect several of these reactions are taking place in the roast.   You'll get caramelization at a higher rate at modest  temps, then more emphasis on Maillard products before 1st crack, then only after 1C is there much oil exposed for any possible fatty browning.  Somewhere after 1C there is also starch browning & the potential for real charring. 
 
</TL;DR>


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You are worried about drying the beans more?  You are heating them up to 425 degrees or so.. yer gonna dry them out bud.


My point is that you don't want them bone-dry before 1st crack, and you may want to retain some water vapor in the roasting chamber rather than blow it straight out rapidly.  .  Moisture is necessary for the maillard reactions.  Believe it or not your beans are still leaking some internal moisture from inside as they hit 1st crack & that this is important for flavor development.

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I havent compared the two methods really.  I may if I get time, do a run through my behmore of say 12 oz and run in the artisan and see if I can tell any differences in them.  Im sure there will be as the methods are way different but I'll see.      Sorry bud I am not roasting 10 batches though.


Any  details would be appreciated.  Yeah  - I've never been one who believes you can get the same roast on differing hardware - too many variables change.  Getting the same roast on same hardware is hard enough.


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This is the sort of thing I'm considering as a flavor issue
https://www.youtube.com/watch?v=TjVas7jbOUI&ab_channel=MillCityRoasters%2CLLC
https://millcityroasters.com/roaster-news/airflow-settings-use/

The Mill City guys are considering how airflow impacts drum roasting (IIRC that's BoldJava in the back seat narrating).
So they start the drum roast with just a modest airflow to encourage an even roast by convection ,then as they approach 1st Crack they but up the airflow.

Several sources talk about removing the "charry" flavor of some no-fan drums by adding a blower.  I'm pretty certain that's what I am tasting on my SC/TO, tho' I used the word 'tarry' above.   If you taste the bitter brown 'varnish' that accumulates on your hardware you 'll know what I am referring to.  i just don't want it on my beans.

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IMO air popcorn poppers are poor roasters (tho' a reasonable starter position); I'd interpret my long-ago air-popper experience as ...
= must modulate the rate of roast by change the load of greens amount, or use a variac.
= results are clean (less charry/tarry) b/c of the air-flow (no smoke deposition).
= results are very even due to (air) convective heating.
= results are often brighter (more acidic) b/c the beans are roast so fast [in my popper experience] so that the interiors are more raw and acidic.
= results are a bit 'plain' (lack of sweetness & complexity) b/c they dried out too much to allow enough development of Maillard products.

IMO the SC/TO has the following characteristics
= must modulate the rate with load and on/off or proportional heater control.
= results are not clean (more charry/tarry) b/c of the smoke re-circulation to the beans.
= results are sufficiently even but requires the stir-arm to be properly adjusted.
= results can be roast thoroughly (neither too bright, acidic, nor too flat and baked ) but this requires adjusting the load size & profile.
= results can exhibit good sweetness & complexity (does not over-dry beans as much as a no-controls popper)

« Last Edit: January 27, 2017, 11:26:21 PM by stevea »
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Offline Ascholten

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Re: I wanna build a new roaster, but ....
« Reply #13 on: January 28, 2017, 02:29:13 AM »
Using an air pop corn machine for your experience with a fluid bed, while yes, IS a fluid bed, is a horrible example to use as a standard.  That would be like driving a Yugo and saying all foreign cars are shit, look at this one!  I could roast coffee in a little over 3 minutes in my air popper.  Way too fast.

Going too fast can make a roast bright, and you can do that with ANY roaster, not just the fluid bed types.  I am sure there is residual humidity leaking out of the bean during roast, however don't discount the humidity that is in the air too.  Why not roast in a steam room if you are worried about having enough moisture for your beans?  Throw in a 230 Kv power supply / jacobs ladder and the water will engulf the smoke molecules, and promptly be ionized and deposited on the walls for easy cleaning.  There, not in your coffee anymore.

Too much heat dries out the beans too much so there's no water left to do the reaction you want.... too much heat speeds up the process too fast as well.   If your beans are bright slow down the heat input and the overall roast time.

It sounds to me like you are trying to talk yourself out of a fluid bed roaster, which is fine, build a drum roaster, both make equally good coffee, although those selling one type over the other will try to convince you otherwise.

If someone owns a business, or has a vested interest in it, don't blindly take their advice on how to do something as gospel, because of course the best way, is going to be their way, the way they are selling etc.

Aaron
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Offline peter

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Re: I wanna build a new roaster, but ....
« Reply #14 on: January 28, 2017, 10:35:00 AM »
IMO the SC/TO has the following characteristics
= must modulate the rate with load and on/off or proportional heater control.
= results are not clean (more charry/tarry) b/c of the smoke re-circulation to the beans.
= results are sufficiently even but requires the stir-arm to be properly adjusted.
= results can be roast thoroughly (neither too bright, acidic, nor too flat and baked ) but this requires adjusting the load size & profile.
= results can exhibit good sweetness & complexity (does not over-dry beans as much as a no-controls popper)

Why not simply design a way to remove the smoke on a SC/TO?  Say a spacer with an adjustable slot to let the smoke out.  I'd be interested to hear your thoughts on bean surface porosity, and whether the beans producing the smoke are simultaneously able to accept a coating/deposit.



Here's a thought for you Steve...  I don't think Aaron and I have the same greens on hand, but you could arrange for us to each roast the same coffee - me on my Ambex, he on his Artisan - and send them to you.  I could even roast some of that coffee on my (properly ventilated SC/TO  ;) ) for your experiment. 

One question that presupposes this whole thread, and I don't mean to me snooty one iota; will your palate be able to discern the difference?  There's a portion of the coffee world that has geeked out to the nth degree over such minutia (not saying this discussion is minutia) and I always say to myself, "You can't taste the difference resulting from the changes you're making."
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