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300F to 350F (150C to 175C)
seedlings
Up to 300F is drying , 350-390F is sugar caramelization, what is happening during the roast from 300F to 350F?

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
Unta
Im posting this W.O.W thinking that it was a pretty concise overview of What makes coffee brown and resonable place to start, thinking that between 300 and 350 coffee starts to brown.

Maillard Reaction, Strecker Degredation and Caramelisation
June 20th, 2006

In the next of my apparent series of articles on all things coffee and chemistry I am going to tackle in a pleasant (I hope) depth these three types of reactions as they appear all the time in coffee articles. Obviously we are going to need to get into a bit of chemistry but hopefully it will remain understandable!

All of these are forms of non-enzymatic browning – opposed to reactions causing foods to go brown because of one of many enzyme actions, such as your apple turning brown when bitten into and left for a bit. This seems an obvious distinction, but I think it is important to include.

As usual – questions or mistakes in the comments!

The Maillard Reaction

Luis-Camille Maillard was the chemist after whom these particular reactions are named, as he was one of the first to investigate them in 1912. The term describes a very specific set a reactions – browning reactions occuring between amino acids and reducing sugars.
Amino acids are the building blocks of proteins, and just as the 26 letters of the alphabet can be used to write an infinite number of different texts, the 20 standard amino acids are put together to create a potentially infinite number of different proteins.
I won’t dwell on the chemistry but all amino acids have the same end to the chain:

The R symbolises the rest of the chain, and obviously this is the bit that is different from amino acid to amino acid.
So anything with protein in it is a candidate for the maillard reaction. All we need now is the presence of a reducing sugar.

The term reducing sugar implies something more interesting than what we find. Simply put a reducing sugar is any sugar with an aldehyde group. We often talk about aldehydes in coffee’s complex aroma chemistry (such as benzaldehyde – which has the characteristic smell of bitter almonds, and is used in just about any almond syrup), but to be an aldehyde means you have to have this arm tacked onto the molecule somewhere:

(again R is the the Rest of the molecule)
A list of reducing sugars is full of familiar names: fructose, glucose, lactose and maltose to name a few.
However, and this is important, sucrose – table sugar – is not a reducing sugar and takes no part in the Maillard Reactions (but does get involved in caramelisation).

These two react together and form new molecules with a brown colour – melanoidins (which you may recall being quite important to crema). Heat is not absolutely necessary, you could mix the two, put them in the fridge and they would turn brown – just very slowly! Heat helps speed the whole thing up. Equally they can happen with water present, but water slows it down. Without the sugar there can be no browning – this is why quakers stand out in roasted coffee, and are so pale.

Problems arise in the full description of reactions because different sugars and different amino acids produce different molecules, and then to complicate the picture these molecules begin to react and interact further. It is almost a cascading set of reactions. Therefore there are a great deal of different compounds created, both aromatic and non-volatile.

There is of course commonality between Maillard Reactions in different food products – coffee and chocolate share a great deal in terms of flavour as many of the same reactions have occured. Roast beef should also share some similar chemistry to roasted coffee, though whether there is enough commonality to make the combination palatable is debatable (though I have a collection of recipes for roasted and barbequed meat with a coffee crust!)
The Maillard reactions are the reason that milk left on a steam wand quickly turns brown.

These reactions are dependent on a few variables: the different amino acids available, the pH, the amount of water, any salts and the period of time held at a temperature.

The Strecker Degradation

This is one I thought I should include because I see it referenced quite a lot, in any text concerning roasting chemistry and is instrumental in the creation of the brown pigment as well as a myriad of volatile aromatics. It falls under the umbrella of, and requires compounds created by, the Maillard Reactions. Unfortunately this one isn’t so simple to explain.

It involves amino acids again, but instead of reacting with a sugar it is reacting with a molecule with two carbonyl groups, which look like this:

The compounds begin to trade parts of themselves, one of the carbonyl groups ending up on the amino acid (the acid having lost on carbon from its chain) creating an aldehyde as wll as an amino ketone. This is an intermediary stage and reactions continue to create many different volatiles.

I have refrained from making explicit descriptions of groups of aromatics. Ketones could be broadly described as having buttery, caramel flavours but key aromas in both raspberries and grapefruit are ketones.
Therefore I don’t think it is terribly helpful for me to claim that furans taste of this, and aldehydes taste of that….
Perhaps a description of each group of aromatics – esters, phenolics, terpenoids and thiols – would make an interesting article.

Caramelisation

Much slower than Maillard reactions, and requiring much higher temperatures these reactions begin exclusively with sugars. They really begin up around 150C to 180C, with water being lost from the sugar molecule beginning the chain of events. In all cases the sugar is converted to a furfuryl. These are a type of furans that have a caramelly, slightly burnt and also slightly meaty notes. The same compound is produced via a different route in the Mailllard reactions. However it is with prolonged high temperature that many other types of aromas are generated.
Caramelisation is more predictable than Maillard reaction due to less variation in the starting compounds. Without the sulphur or nitrogen found in the amino acids caramelisation is unable to produce flavours as meaty as Maillard reactions

It is interesting to note how the sugar solutions taste changes in caramelisation. A sugar solution initially will be sweet with no aroma. Through caramelisation it becomes both sour and a little bitter, as a rich aroma develops. Generally the longer sugar is caramelised the less sweet it tastes.

Extended Reading:
General Book: The Maillard Reaction
Website: Course Information and A nice Diagram
Coffee Specific: The Science of Quality

Hopefully this will give the reader an insight into the basics of the different types of chemistry going on when you apply heat to food and it turns brown. Because of the broad range of applications I haven’t focused this one completely on coffee, though no doubt that will change when I come to review it. Any mistakes or obvious omissions then please let me know!

http://www.jimsev...elisation/



And with that Sweet marias posts that @ 327 they are considering it early yellow and that its still steaming off water. By 347 they are saying that the beans are showing signs of browning.

Sean
Sean Harrington
educate.
 
http://www.untacoffee.com
David
seedlings wrote:
Up to 300F is drying , 350-390F is sugar caramelization, what is happening during the roast from 300F to 350F?CHAD

Hi, CHAD. I had the impression that the drying phase was a range, centered around 300F plus or minus around 20 degrees, generally the phase when the beans move from green to at least a medium tan, YMMV. Logically, the beans don't seriously start to dry until above 212F, with the surface giving off vapor first and then more drying occurs as the heat penetrates to the center of the bean. Meanwhile the outer surface starts to brown. The browning doesn't have much to do with the drying, but does give an decent indicator of the drying phase.

More to the point of your question (discussion starter), the innards of the beans are "loosening up" chemically. That level of heat allows amino acid chains to be freed up so that they can combine with reducing sugars when the time comes. This combination process gives the different flavor characteristics that we are looking for and that, thankfully, we can influence to some degree by the profile we chose.

Great question, CHAD.

Comments?

================
Shock
OMG, Sean beat me to the punch. He also types so much faster than I do. And uses a lot more concise and relevant information, too. Nice post, dude. :Clap:

BTW, SweetMarias is using typical roasting chamber temperatures. I was referring to actual bean temperatures.
Edited by David on 12/05/2011 5:04 AM
 
seedlings
Good insight fellas. Sean, this is the interesting line: "Generally the longer sugar is caramelised the less sweet it tastes." Hmmm... This is the opposite of what I thought for some reason. I had in my mind that slowing down the caramelization process increased sweetness- but can't put my finger on where or why I though that.

I'm beginning to think that the 300-350F segment is where 'roast' flavors develop. If you want a 'meatier' coffee this phase should be slowed, if you want a refined or delicate (can't find the right word) coffee, then speed this phase up.

CHAD
Edited by seedlings on 12/05/2011 5:30 AM
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
wsikes
So... is it the furfuryls produced during caramelization than can give the coffee a "tinge" of a burnt taste even though the roast has not progressed to a very dark stage?
William Sikes
 
Unta
seedlings wrote:
"Generally the longer sugar is caramelised the less sweet it tastes." Hmmm... This is the opposite of what I thought for some reason. I had in my mind that slowing down the caramelization process increased sweetness- but can't put my finger on where or why I though that.


CHAD


Its true, carmel gets less "sweet" but more "tasty" and complex as it darkens, in my limited experience.

Maybe the 355ish to 370 needs to be the slow or stall time. Maybe the slow doesn't need to continue all the way to 390.
So for instance 355-375 at 10/ then jump up to what ever your typical cadence is from 390 on.
Ill run some samples later, see if there is any noticeable difference.
When you say meatier, are you speaking to body or flavor.
I also wonder if slowing down the phase prior to carmelization impacts the carmelization by reduction of moisture. It most certainly does...but in what way.

Sean
Edited by Unta on 12/05/2011 6:11 AM
Sean Harrington
educate.
 
http://www.untacoffee.com
seedlings
Meatier - I mean indistinct roasted coffee flavor.

CHAD

*edit: I'm kind of thinking about it this way... the roasted flavors you get on items baked in your oven at 350F. Cookies bake, but sugars aren't as caramelized as they would be at higher temperatures. You couldn't 'burn' bread at 350F, but you can make dry toast.
Edited by seedlings on 12/05/2011 6:33 AM
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
JackH
I can tell you that dwelling too long from 300F to 1C brings out a very nutty/woody flavor for my roasts. I don't care much for it so I try to speed to 1C as fast as I can.
---Jack

KKTO Roaster.
 
seedlings
JackH wrote:
I can tell you that dwelling too long from 300F to 1C brings out a very nutty/woody flavor for my roasts. I don't care much for it so I try to speed to 1C as fast as I can.


I tend to think the same thing, but I keep reading about 'drawing out sweetness and complexity' and things like that by stretching out that phase... I'm looking for evidence.

CHAD
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
Unta
JackH wrote:
I can tell you that dwelling too long from 300F to 1C brings out a very nutty/woody flavor for my roasts. I don't care much for it so I try to speed to 1C as fast as I can.

Just curious, when you say speed to first crack what does that mean with your roaster?
How fast is speeding?
Sean
Sean Harrington
educate.
 
http://www.untacoffee.com
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Unta
I wonder if a a lack of moisture in the electric heat machines might have something to do with it....
Sean
Sean Harrington
educate.
 
http://www.untacoffee.com
JETROASTER
Unta wrote:
I wonder if a a lack of moisture in the electric heat machines might have something to do with it....
Sean


I'm wondering if this all differs between drum and air-roasting? -Scott
 
JackH
Unta wrote:
JackH wrote:
I can tell you that dwelling too long from 300F to 1C brings out a very nutty/woody flavor for my roasts. I don't care much for it so I try to speed to 1C as fast as I can.

Just curious, when you say speed to first crack what does that mean with your roaster?
How fast is speeding?
Sean


I initially set turbo oven heater power to get a rate of rise that will give me 4-5 minutes to 300F for drying. Once I am at 300F and the beans are yellow, I increase power (speed up) to get to 1C fast. Usually takes about 3-4 minutes. Then I reduce to keep the roast from running away. With the unheated garage, it is taking longer for me. I never allow ET to go above 500F or it will run away.

When I started out all my roasts were sour. The key for me was enough drying time and letting there be enough time after 1C without going to a full 2C.
---Jack

KKTO Roaster.
 
JackH
seedlings wrote:
JackH wrote:
I can tell you that dwelling too long from 300F to 1C brings out a very nutty/woody flavor for my roasts. I don't care much for it so I try to speed to 1C as fast as I can.


I tend to think the same thing, but I keep reading about 'drawing out sweetness and complexity' and things like that by stretching out that phase... I'm looking for evidence.

CHAD


I think some of the sweetness also comes later after 1C, at least I can sometimes smell the roaster smoke go from a sour/vinegar to a nicer smell.
---Jack

KKTO Roaster.
 
Unta
JackH wrote:


When I started out all my roasts were sour. The key for me was enough drying time and letting there be enough time after 1C without going to a full 2C.

Jack,
What is your optimal time between the cracks?
Sean
Sean Harrington
educate.
 
http://www.untacoffee.com
JackH
Unta wrote:
JackH wrote:


When I started out all my roasts were sour. The key for me was enough drying time and letting there be enough time after 1C without going to a full 2C.

Jack,
What is your optimal time between the cracks?
Sean


Sean,

My latest time to 1C on the Sumatra is about 10 minutes. I usually don't go to 2C but reduce power (4-5 deg/min?) after 1C for at least 3 minutes, then dump. Still trying to figure out what the optimal time would be.
The SC on the graph should have been a END, I pressed the wrong button.
JackH attached the following image:
sumatra_web.jpg

Edited by JackH on 12/07/2011 12:48 PM
---Jack

KKTO Roaster.
 
JackH
In my haste and enthusiasm, I hope I did not hijack or go off the original topic.
---Jack

KKTO Roaster.
 
farmroast
I've yet to find any details on temp. profiles within 280f-360f
Generally we're in the 20-25degrees/min range. It's not a hard part of the roast to make some adjustments if we knew more about the effects of changes.
Maybe it's just another one of things we are going to have to test.
Ed B.
DreamRoast 1kg roaster, Levers, Hand Mills http://coffee-roa...gspot.com/
 
seedlings
Unta wrote:
JackH wrote:
I can tell you that dwelling too long from 300F to 1C brings out a very nutty/woody flavor for my roasts. I don't care much for it so I try to speed to 1C as fast as I can.

Just curious, when you say speed to first crack what does that mean with your roaster?
How fast is speeding?
Sean


I can get two pounds to first crack in about 8 minutes, but generally it's 10-12 minutes. So that's what... 40F/min on average?

CHAD
Edited by seedlings on 12/08/2011 4:07 AM
Roaster: CoffeeAir II 2# DIY air roaster
Grinder: Vintage Grindmaster 500
Brewers: Vintage Cory DCU DCL, Aeropress, Press, Osaka Titanium pourover
 
Unta
JackH wrote:
In my haste and enthusiasm, I hope I did not hijack or go off the original topic.

No Worries.
Sean
Sean Harrington
educate.
 
http://www.untacoffee.com
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