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Smoke? What stage of the roast cycle?
vuvuzella
I've just cobbled together a rudimentary roaster out of a bread machine and heat gun. I was following a page on Sweet Marias that listed the stages of the roasting cycle. I was wondering at what stage the beans start to smoke?

I've notice this around 1st crack. I'm on my second batch of coffee and I must say the first batch although not as strong as I'd like was excellent - HD video to follow!! (I am waiting for a thermometer to be delivered and I'm sure this will help)

Cheers
Richard
Edited by vuvuzella on 08/24/2010 8:16 PM
Beaner
Greetings Richard.

I can't answer your question from experience but this video might help some. I think it might even be from a HRO member. I'm still working on my BM/HG.

There is a part 1 and part 2 of the video:

http://www.youtub...r_embedded

Edit: Yep, the video is Chad's (Seedlings) BM/HG video. Reference this link on CS:

http://www.home-b...ml#p108646

Hope this helps a little, it's a great video.

- Ron
Edited by Beaner on 08/24/2010 9:30 PM
Unta
Richard,
Though I've never roasted using a bread machine. Smoke around first crack most likely is associated with the chaffe not the beans them selves. Beans wont start to smoke untill the onset of second crack. Though my observations have all been using air roasters.
sean
Sean Harrington
educate.
Randy G
With an air roaster it can be difficult to see the smoke.. the more air and the less coffee exacerbates that situation. I have never documented the actual smoke occurrences, but from memory, at around 275 to 300 or so you will smell some grassy smells which might be accompanied by some visible emissions (smoke and water vapor possibly), but it will be more of a grassy smell. At about 325 to 350 or so the smoke starts- whether you can see it is another story. By the beginning of first crack the smoke should be quite visible, and at second and at active second there will be a good amount of smoke.

If you need more data than that let me know and the next roast I will pay more attention. But more importantly, it is critical to use two thermometers in such an uncontrolled device (that is, with no electronic way to accurately control the heat). One thermometer should be in the bean mass and the other one monitoring the air temperature around (above?) the beans. This is very difficult to do with a heat gun. I have a roasting Profiling article on my website you may want to read that will fill in the gaps f why this is important. Pay particular attention to the part that describes the drying phase (around 285 to 310 degrees).

Life's too short to drink bad coffee.
endlesscycles
Smoke occurs at Fahrenheit 451 and above. So do true exothermic reactions. Burning of cellulose is what is going on.
-Marshall Hance
Asheville, NC
Randy G
I roasted this AM in my Hottop and took some notes in regards to smoke production. The bean temperature is from a probe through the back wall that is in the bottom of the bean mass all the time. The environmental temperature is from another probe at the top, inside of the drum

Smoke Description ET BT
1st light smoke appears 312 310

Very steady light smoke 323 331

Light- like a lit cig. 330 331

medium light steady 348 373

first crack begins 356 385
smoke increases

medium very noticeable 365 399

1st ends - steady heavy 377 425

2nd begins - steady heavy emissins

Be aware that these temps are from my thermocouple and do not necessarily reflect "industry standards" of temperature points of a roast.

Additionally, using the term "smoke" is just to describe all visible emissions from the roaster. These are particulate matter, water vapor, or whatever else I see. They are not necessarily the product of true combustion.


Life's too short to drink bad coffee.
seedlings
Even with the breadmaker and heatgun you should see results much like Randy's post above. I notice wispy smoke in the mid 300s, steady grey smoke from first crack on. I very rarely go to a rolling second crack, but that brings dark smoke.

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
Ringo
It does seem to me that extra smoke early is a sign I am pushing the roast too fast. If I get much smoke at 310 to 330 deg F I will back the heat off a little. I always get a little just do not want to get a lot. I am a nubbie at this roasting game.
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
endlesscycles
I wouldn't worry too much about emissions beyond getting them to go outside. Roast, record, taste, repeat. Record by whatever means you have, and learn to decide what matters by your own judgment.
-Marshall Hance
Asheville, NC
JETROASTER
Do any sugars get lost during these early stages? (300-350 degrees....roughly) -Scott
ginny
Richard:

they smoke a lot when they burn!

they will usually smoke maybe going into 1st crack, a few snaps

really depends on the heat source and the bean movement.

the amount of beans and the type of roaster you are using.
smoke is not a parameter for a good/bad roast.

what bean?

ginny
seedlings

Quote

freshbeans wrote:
Do any sugars get lost during these early stages? (300-350 degrees....roughly) -Scott


If I remember, sugars begin to take shape around first crack.

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
JETROASTER

Quote

seedlings wrote:

Quote

freshbeans wrote:
Do any sugars get lost during these early stages? (300-350 degrees....roughly) -Scott


If I remember, sugars begin to take shape around first crack.

CHAD


That part I've got, however, somewhere(?) I remember reading that at a particular temp, sugars would 'cleave' and potentially bind with H2O.
My concern is that if my beans are 'forced' with too much moisture present, I could 'steam-out' some valuable sugars.
This probably belongs in a differant thread, but my etiquette sucks.
-Scott
seedlings
How would you roast differently if the temp is lower, like 330F or 212F?

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
JETROASTER
I would likely enter the roast quickly(usual), slow down at the point where moisture could exit(below the point of cleaving) without taking the sugars with it . Let the moisture leave gently (preserving sugars). Speed things up after the H2O is gone.
I've been looking around trying to find the article. I thought it was a wiki thing having to do with sugar chemistry. That's all I know so far. -Scott




JETROASTER
I must have read something without drinking coffee first.
I haven't found anything to suggest that sugars 'leave' the bean during roasting. I've found plenty on the chemistry etc.....So, I'm chalking it up to old age.
...On with the roasting!!! -Scott
allenb

Quote

freshbeans wrote:
I would likely enter the roast quickly(usual), slow down at the point where moisture could exit(below the point of cleaving) without taking the sugars with it . Let the moisture leave gently (preserving sugars). Speed things up after the H2O is gone.
I've been looking around trying to find the article. I thought it was a wiki thing having to do with sugar chemistry. That's all I know so far. -Scott


OK, all hands on deck!

We need to find a way to compile all useful info to do with drying (right way/wrong way), best way to preserve sweetness, body etc... which seems to be in various papers and articles by Staub, Boot, food chemistry experts in Europe (Nestle, Illy...) and once and for all extract just the useful stuff, leave out all the techno-geek filler so we can all come back to it when needed to "tune" our roast.

Who within Homeroasters would 1. know where these articles are, 2. be wiling to extract the good stuff and condense it, 3. place it in the downloads area of our forum?

We could break up the duties to make it less cumbersome.

Anyone game?

I'm willing to put in some of the effort.

Allen
1/2 lb and 1 lb drum, Siemens Sirocco fluidbed, presspot, chemex, cajun biggin brewer from the backwoods of Louisiana
Ringo
This is a cut from a thread on GCBC, by Buttwisker.
This is not a trivial topic that easily can be answered in a concise post. I started collecting peer-reviewed journal articles a couple of weeks back about coffee chemistry, as I have realized that there is a need for a book about coffee chemistry and home roasting at an intermediate level, something that falls between the Davids book and the Flament book. The Kenneth Davids book is a good intro for beginners, but the Flament book and the literature papers are beyond most folks. I intend to spend some time this winter putting together a book that will treat this topic at an intermediate level.

Some of the papers in the primary literature have astounded me! I am learning an awful lot in the process of researching this potential tome. While Larry's description is quite accurate, it is more focused on the physics than the chemistry of the roasting process.

I think to hit it in brief off the top of my head:

There are many compounds of varying reactivities in green coffee beans. These compounds react with each other and their environment regardless of the temperature that they are at, but the rate of these reactions increases with increasing temperature. (A basic rule of thumb in organic chemistry is that for every 10?C (18?F) increase in temperature, the reaction rate will double for a first order reaction.) As coffee beans are heated, the vapor pressure of the various components within the bean increases. So as well as having a increase in the rate of reactions between the bean constituents, we also are driving the lower boiling compounds out of the bean. Water is usually about 11-14% of the green coffee bean's initial mass. As the bean is heated approaching the boiling point of water (100?C or 212?F), the water is lost from the bean - however much of this water expands and destroys cellular walls within the bean during this process of leaving.

The bean turns yellowish and a grassy or grainy smell (kind of like popcorn) is evidenced as the bean is dried out - this grassy smell consists of fragmented hydrocarbons such as isoprene and other low boiling organics. By the time the bean temperature reaches 300?F, the initial water mass has been driven off (however, more water is being gradually produced through the degradation of other compounds within the bean). When the bean reaches approximately 350?F, the sugars within the bean begin to caramelize. This is a process where the carbohydrate chains begin to interlink and react with each other. Different sugars caramelize at different temperatures, at different rates, and with each other as well. Caramelized sugars are more stable than sugar molecules, and allow sweetness to survive beyond temperatures where sugars would be converted to compounds that are not sweet.

As the temperature increases slightly higher, the Maillard reactions begin. Maillard reactions consist of reactions between sugars, caramels, lipids, and proteins. The products of Maillard reactions are usually heterocyclic compounds (carbon-based rings with oxygen or nitrogen linked into the ring), and give coffee it's 'roasted' flavor. Compounds such as furans, pyrazines, and pyrroles are the result of Maillard reactions. Strecker reactions begin at slightly higher temperatures yet - these form various aldehydes from the starting materials of the beans and from compounds formed in these other reactions. The amazing thing about these concerted reactions is that they all occur at different rates, temperatures and they compete with each other. This is why slight changes in a roast profile with the same bean can result in entirely different flavors in the final roasted product - slightly altering the temperature ramp will result in conditions that favor different end products.

Larry covered the physics of the first and second crack quite well - and these can occur at different temperatures based on the ramp rate - as the beans will have different extents of dryness, expansion, and fracture based on that ramp rate. The first crack involves the splitting of the seam and the loss of the remaining silverskin. This usually occurs past the temperature where caramelization occurs, and caramelization is a relatively slow process, so if you do a fast ramp to the first crack, you are missing out on caramelization in favor of Maillard and Strecker products. With less caramelization, there are more sugars to form Maillard and Strecker products, so the bean will get an extra pungent roastiness and acrid flavors, as well as chocolates and nuts. Conversely, if a slow ramp to the first crack is taken, with a healthy pause in the range of 350-375?F, there will be more caramelization and less Maillard and Strecker products. This results in a sweeter roast.

While some of the signature flavors are present by this point, some of the organic acids, esters, and aromatics that give coffee it's signature fruitiness, spiciness, floral, chocolate and nutty characteristics are formed in the pause between the first and second cracks. For this reason it is frequently advantageous to have a period of several minutes between the completion of the first crack and the first vanguard snaps of the second (or the end of the roast - depending on your target roast level). Too long of a period will drive off some of those compounds, resulting in a baked flavor.

As the temperature of the bean approaches 450?, combustion of the organic compounds occurs, as oxygen reacts with your tasty flavor compounds, breaking them down into water, carbon dioxide, and charcoal. Many of the fragile tasty compounds get hydrolyzed by the water and begin to be not-so-tasty compounds. Eventually if the roast continues you wind up with nothing but charcoal.

Say we just roasted our beans to Full City, right before the second crack begins. The cellular matrix of the bean has been compromised, and many oils have been formed, but they are almost entirely within the structure of the bean. Bits of combustion that have occurred have resulted in carbon dioxide entrained in that oil. Carbon dioxide weighs 44 grams per mole (a mole is a unit of a whole bunch of molecules, basically a 6 with 23 zeroes after it). At standard temperature and pressure (basically room temperature and sea level air pressure) a mole of a gas molecule, such as carbon dioxide, will fill 22.4 liters. That is why a couple hundred grams of roasted coffee will give off so much carbon dioxide as it degasses over the first couple of days - the degassing being the CO2 leaching out of the oils within the bean. Anyway, by rapidly cooling the beans and getting them into a container evacuated of oxygen, we prevent further oxidation of the oils in the coffee (oxidation of oils is what causes bacon to become rancid). That is why I prefer to quickly cool the beans with a fan or shop-vac cooler, get them into a valved bag, and then suck all of the air out of the bag with a vacuum.

I guess I could go on rambling forever, and nearly every sentence in this post could (and likely will) be elaborated upon to a paragraph or more, and there are so many related side topics, that this should fill up a book. I intend to reference my statements with footnotes referring to the original primary literature articles for most of my points. And hopefully this won't be another one of those undertakings that starts off with grand intentions then dies in a quagmire of procrastination...

=BW=
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
John Despres
Ringo, post a link to the original, please. Thanks!

Great article by BW, too.

John
Respect the bean.
John Despres
Fresh Roast 8, Gene Cafe, JYTT 1k, Quest M3, Mazzer Mini, Technivorm, various size presses and many more brewers.
Ringo
http://www.greenc...pic=3679.0 Yea this is Buttwiskers lessons. This man knows coffee.

Edit - made link clickable JD
Edited by John Despres on 08/28/2010 12:01 PM
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
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