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Color is just one of the ways to determine degree of roast. By itself, it is of limited use. When complemented by the audible cues (first and second crack) and the aromas of the roast process, it is extremely informative . Here is a You Tube video showing the color changes that occur during roasting –
|Degree of Roast, Temperature, Description
This coffee was roasted on my Probat 12 kilo so I could take advantage of the sample trier. Ignore the times, and take the temperatures as a ballpark figure.
The important thing is here is to see the transformation the coffee goes through as it roasts and what look, color, bean sizeand surface texture, corresponds to the degree of roast. ***(see note from home roaster George Steinert below).
Roasting is more about exceptions than rules. I have this page about bean color vs. ground coffee color that might be helpful. So get to it.
|(click on preview for full size image)|
1. Green unroasted coffee 0:00 – 75 f
This is a wet processed, Central American coffee, a accidental blend I have had sitting around. Each photo here are different coffee seeds from the batch I roasted sosize and shape will vary seed to seed.
2. Starting to pale 4:00 – 270 f
Drum roasters take a long time to transfer heat to coffee so there is little change in the first few minutes. In an air roaster coffee gets to this stage so much faster because of the efficient heat transference of the rapid moving air stream, so the whole warm-up phase can be as fast as two minutes.
Odd looking seeds – the near one might be a Kona Typica and the farther one perhaps the traditional Bourbon cultivar or Mundo Novo. Click on image for large photo, or here for multi-bean photo
3. Early yellow stage 6:00 – 327 f
At this point the coffee is still losing water in the form of steam and no physical expansion of the bean has taken place. The coffee has a very humid, hay-like smell at this point. All of these warm-up stages leading up to first crack are part of an endothermic process, as the coffee takes on heat, leading to the first audible roast reaction, the exothermic 1st crack.
4. Yellow-Tan stage 6:30 – 345 f
The roast is starting to assume a browner color, and a marbling appearance is starting to emerge. No bean expansion yet. The first “toasty” smells (toasted grain, bread) can be detected, and a bit less wet, humid air coming off the coffee. Note that some coffees turn a brighter and more distinct yellow at this time, such as Costa Rican and Mexican coffees.
5. Light Brown stage 8:00 – 370 f
First crack is drawing near at this point. Some bean expansion is visible as the central crack in the coffee has opened slightly. The coffee releases some silverskin or chaff.
6. Brown Stage 9:00 – 393 f
Now we are right at the door of first crack. The coffee has browned considerably, which is partly due to browning reactions from sugars, but largely due to another browning reaction called the Maillard Reaction (which also is responsible for browning of cooked beef!)
7. 1st crack begins 9:20 – 401 f
At this point, the very first popping sounds of the First Crack can be heard. This sound can be similar to popcorn pops (in distinction to the sound of the Second Crack, which has a shallower sound, more like a snap). At the point of first crack the internal bean temperature would be around 356 f.
8. 1st crack under way 10:00 – 415 f
As first crack continues the coffee still appears mottled and uneven in color. The coffee starts expanding in size and shows visible cracks. The amount of chaff in the crease of the seed is noticeably less.
First crack is an exothermic reaction; the beans are giving off heat. But then the beans quickly become endothermic, meaning that a roaster that is not adding enough heat to the process will stall the roast at this point …not a good thing. Once caramelization begins (340-400 degrees internal bean temperature) a roast that looses heat will taste “baked”, perhaps due to the disruption on long-chain polymerization. The melting point of sucrose is 370 f and corresponds to this window of temperatures when caramelization begins.
9. 1st crack finishes 10:40 – 426 f
This is considered a City Roast. First crack is done and the roast is stopped.
Notice the bean surface is smoother somewhat from expansion but still has darker marks in the coffee, like a finely etched pattern. The edges of the seed are still fairly hard. At this point the coffee starts giving off carbon dioxide.
10. City+ roast 11:05 435f
City+ means the coffee has cleared first crack, and time is allowed for an even bean surface appearance to develop.
There are only very small changes between the #9 picture above and this one, notably the edges of the bean are a bit softer. The whole stage between the first and second crack is a short period ( 15 to 30 seconds) where a lot is happening chemically to the beans. The coffee gains heat once again until its woody cellulose matrix, the bean structure itself, begins to fracture … that is, the Second Crack.
11. Full City roast 11:30 – 444 f
This image represents a Full City roast; the coffee is on the verge of 2nd crack. This might be hard to judge the first few times you roast; after a while, you will have a feel for it. The beans are have a slight sheen of oil and the edges are softer.
The internal bean temperature for second crack normally is 446 degrees farenheit. But in fact second crack is a bit less predictable than first crack, in my experience. Why? It could be due to the fact that first crack is the physical expansion of the coffee seed as water and carbon dioxide split and CO2 outgassing starts. Second Crack is the physical fracturing of the celllose matrix of the coffee. This matrix is both organized cellulose that reacts readily to heat, and not-so-organized cellulose that does not. Since every coffee is physically different in size and density due to the cultivar, origin, altitude, etc., it make sense that the particular cell matrix is different too, and not as universally consistent.
12. Full City+ roast 11:50 – 454 f
The darker side of a Full City roast is Full City +, where the coffee has barely entered 2nd crack. A few snaps are heard, and the roast is then stopped. Second crack may continue into the cooling phase – this is called “coasting”. The more effective and rapid your cooling – the better your ability to stop the roast at the degree you want.
Compare the full size images from the Full City roast and this one, and I think it is easy to see a difference. Well, maybe not easy, but the Full City+ roast is a bit fuller, more small cracks on the face (or flat side) of the bean.
13. Vienna – Light French roast12:15 – 465 f
The Vienna stage (also called Continental) to Light French stage is where you begin to find Origin Character eclipsed by Roast Character. A dark or heavy roast is at odds with buying coffee for its distinct origin qualities. Dark roast coffees tend to taste more like each other – as the differences due to distinct origins are obscured by the carbony roast flavors. Nontheless, some coffees are excellent at this stage (our Puro Scuro blend is engineered for this roast range).
By the way; Espresso is not a roast. But Northern Italian style espresso is usually roasted to 440 – 446 internal bean temperature. Southern Italian (Scura) is generally a Light French Roast or a tad darker.
14. Full French roast 12:40 – 474 f
Sugars are heavily caramelized (read as burned) and are degraded; the woody bean structure is carbonizing and the seed continues to expand and loose mass. The body of the resulting cup will be thinner/lighter as the aromatic compounds, oils, and soluble solids are being burned out of the coffee and rising up to fill your house with smoke. 474 is well beyond any roast I do on the Probat. I will go as high as 465 on a couple blends, and that’s my limit.
Notice how fast and dramatic the change is from the previous photo – all that happened in less than 30 seconds!
15. Fully carbonized 13:00 – 486 f
At this stage, the coffee can be over 25% ash; it is carbonized, dead, charcoal.
16. Imminent fire … 13:30 – 497 f
This bean is right at the verge of fire – in fact you can actually start a fire with a large batch once you dump the coffee out of the roast drum into the cool tray. The sudden rush of oxygen might be the needed ingredient for cafe del fuego. Kids, grab your marshmallows! Hope you like ’em smokey!
Needless to say, this roast level is full-on carbon and you can write your name with a coffee bean. The bean size here is smaller that photo 15 due to the randomness of the seeds selected to photograph – coffee does not get smaller at this stage…
|***Note from George Steinert, home roaster: “I see a lot of new users of the iRoast2 struggling to make sense of roast levels. I have been using the iR2 since February. I got the best success when I added the digital thermometer with thermocouple probe (both from SM) and condensed the well-documented “degree of roast” information on the SM web site into a one page chart (below). By using the temps on the chart (as measured with the thermocouple planted in the bean mass) as a “guide” and when combining that with actual experience of hearing the cracks (when they can be heard through the fan noise), the color, the smell, and the time (when using a consistent load of green beans), I have had very predictable results. I continue to use the chart as my baseline of understanding when roasting with the RK drum which I started using in June. I reference the start and end of first crack to tell me how the roast is progressing. After a while, the aroma becomes a factor. About 60-90 seconds before first crack begins, I swear I can tell it’s coming because of a characteristic aroma. Primarily I use the sounds of the crack(s) and secondarily, the time. With the iRoast2, the temp from the thermocouple gives a pretty reliable indication of where they are in the roasting process…given some flexibility regarding start and end of first crack depending on the type of beans. With the iRoast, you also have the helpful cues of color and seeing what’s happening on the surface of the bean. Users should note that First Crack is not going to necessarily begin when your thermocouple hits 401 degrees F nor end when it hits 426 F but after you’ve done a few dozen roasts you will get the feel for how to overlay the progress of the roast onto the temperatures you are reading.
George Steinert’s Degree of Roast/Temperature chart:
Please note that both Tom and George emphasize that temperature alone will NOT determine degree of roast. Each roaster is different and different beans roast slightly differently as well. All the information on this page is to be take together to help determine degree of roast – no one element (appearance, sound, temperature, etc) can determine degree of roast. Most importantly – TASTE THE COFFEE – and see what that tells you about how it roasted.
Note about High Altitude Roasting
Here is a representative image I took of the Agtron Roast Color Tiles, and might give you a basica idea of the color scale. There is a bit of glare on the left side though (most visibile on Agrton 45). Since this is such an approximation and the appearance depends so much on monitor calibration, etc, I am not going to put a ton of work into this … I am working on a better method of sharing these roast colors information.
For those that have been to Spain, and have fallen in love with the Cafe con leche and the espresso, and have tried to reproduce the taste at home and failed, its not because you made it wrong, its because of the absence of one type of roasted bean in the mix. The sugar roasted bean at which makes up 10-30% of the blend, the Torrefacto.
Encasing the bean in sugar during roasting does two things. It preserves the bean for an extended life, and also uniquely cuts down on the acidity in the taste. This enables a strong tasting coffee without bitterness or the acid bite. I have found that my coffee consumption goes way up when I go to Mallorca or Spain, (and its high to start with ) yet gratefully I dont suffer from increased heartburn. There is something about the taste of torrefacto, so much so that I decided to learn how to make it.
It has taken a year. A year of reading, watching, visiting Roasters in Spain, researching history in USA and in France. It actually is such a simple process but……. too easy to mess up if you want to put the beans through your roaster without destroying your drum or pan with caramelised sugar.
If you have a fancy miniature drum home roaster, dont do this process in it. If you have anything you want to keep as is, dont do this in it. You have been warned.
The only methods of making this are in a metal bowl with a hot air gun, or a Corretto (breadmaker) and following instructions carefully. Im taking no responsibility for your frustration or tears or ruined equipment, thats just the way it is.
The commercial machines used to manufacture torrefacto, are dedicated machines for that job. They have special pouring mechanisms for adding the sugar and special cooling so as to quickly get the sugar to dry off on each bean and not clump together. This is a small unit, the companies in Spain usually use 300-600 kilo machines.
OK.. so here I will tell you how to do it in a Corretto. (This breadmaker is being stripped for a design Im working on..but it still works fine)
Pre heat the drum to 265C and add your green beans. (I roast Torrefacto in 300gram batches) Allow the beans to ‘dry’ by leaving them on the low setting of the gun for 4 minutes or so. (During this time you will see the temp rise about 4-6 degrees a minute). Once the temp is above 130C, watch for the beans colour change to yellowish..raise your heat rate to about 10 degrees C a minute. At about 175-185C add 12% of the green bean weight, of sugar, directly into the roasting beans. Close the lid and keep roasting. At this stage, your Corretto will smoke and smell of burning caramel and neighbours might be thinking that they should call the fire service. Ignore them.
Keep a wooden spoon handy in case you have to occasionally scrape down the sides of the corretto basket if one or two beans stick. DO NOT LOSE YOUR NERVE at this point. Its easy to get panicky when seeing a gloopy mess. If you have followed these instructions concerning weights, there should not be a gloopy mess, if you havent… it will take 2 hours of cleaning involving heat, sand and lots of elbow grease.
Continue roasting the bean of your choice in the pan, to the timings that you like for that particular roast. Now the last batch I did was Old Brown Java, and I like to dump them just at the onset of second crack, however this time I let second crack develop for 20 seconds or so and then dumped.
I dump onto flat roasting tins and shake for 30 seconds so nothing will stick. If Im roasting in the UK.. The weather will cool them off in double quick time.. Once cooled the beans are completely shiny, dry to the touch and no stickiness what so ever. If you crack one open, they look exactly the same as a normally roasted bean.
If there is any sugar left in your basket, and there should not be, just the odd fleck here and there, just proceed with your next non torrefacto roast and the basket will be perfectly cleaned.
I usually mix Torrefacto at a ratio of 20% by volume to the same single origin bean. If I am doing a blend, say 30% Old Brown Java, 20% Malabar, 20% Brazil, I will use 30% Torrefacto. (If I am going for the ‘full’ taste, I will make torrefacto out of Robusta, its a personal choice)
In the cup as an espresso, there is a gentle sweetness and decided lack of too much acidity whilst retaining the strength of the coffee. In a latte.. well I just make cafe con leche. A long pour of coffee and equal amount of steamed milk. It is my favourite milk based coffee.
More so than America, More so than Europe combined, More so than Australia. The U.K. has a furtive little hobby that no one admits to, certainly does not discuss, and is not mentioned in public. BritishCoffeeScene is going to lift the lid right now.
Home Coffee Roasting. Its a spreading hobby throughout the British Isles. Its true. In talking with Artisan Coffee houses, and doing the sums, I can state that between 35% and 45% of bean sales are the raw green beans!
That means approximately half of all sales from specialist coffee Houses are going to individuals who, in one form or another, roast their own. Yet… there is no mention of it, no discussion, no contact through on line forums, no interchange with the supplier about roasting. The beans are sold, the beans arrive at the solitary destination and then… silence. A little while later, the coffee house gets another innocuous order for some more green beans. Noting that the customer has previously bought green beans, the supplier will include a little information pack with references to online forums that discuss coffee roasting, or offer for the customer to take advantage of advice the coffee house gives freely, and…… nothing.
Britain, what gives? Coffee roasting is a proud and noble art. It contains elements of innovation in equipment making, it requires a modicum of skill to bring all the elements together, and it has the capacity to be turned into a full scale home roasting production utilising computers, logs, thermometers, roast times and bean preferences. Around the world, there a clubs and chat boards and people who have never seen each who exchange information and equipment and test results. In Britain? there is a just a request to purchase green beans on the Coffee House Paypal site or Amazon ordering. It stops there.
Although I have use of a professional Toper roaster, what do I use for small batch testing? I have small home made hot air units. I have air guns. I have Stainless steel bowls and wooden spoons. I have adapted breadmakers. I have popcorn poppers. I have Halogen cookers. I have heavy pans. Ive used a lot of the commercially available home roasters too.
My favourite home roaster is a Russell Hobbs “Breadman” breadmaker. I use it weekly making a kilo of coffee in 18 minutes including pre heat time. This is my own machine with a test lid of 2 nonstick roasting pans cut down to size, with the viewing tempered glass sandwiched between them and pop riveted to hold. I drilled the hole tight for the air gun and later will add another hole for a chaff removal system Ive thought of. I will be making a more professional lid for this once my testing is complete with this prototype. I have a the unit linked to my computer via a thermometer.
So why dont I just spend a couple of thousand pounds or more on a “mini” professional system? First, I dont want to. Second, for less than 60 smackers, with this setup, I have the ability to produce equal if not better roasted coffee than most large scale coffee houses.
If you have a computer, and purchase an inexpensive Victor 86c thermometer..and couple it to an amazing FREE software for Roast logging and charting (No, Im not going to tell you where it is unless you come out of hiding and ask for it!)
Perhaps when you home roasters realise its Ok to come out of the closet, and that what you do is fine and wonderful and that there are some of us out here who want to share and learn from each other, you might join in some discussions and forum groups to further information.
When you finish your Roasting. Your coffee should look like this and taste amazing. You will never settle for less.
Coffee Roasting was not something Rob Hodge ever envisaged in his future. After his marriage to Vikki in 2002, Rob and new wife spent their honeymoon in Australia and developed a love for the country during their stay there. When they returned to the U.K. and went back to their industry Jobs, Rob in Telecoms and Vikki in I.T. they never forgot the country of their dreams.
Working hard and saving money, they finally managed to obtain the elusive visa and moved to Sydney in the late 2000’s. Vikki enrolled as a student in catering and worked her way through the rigorous and tough Australian college system which culminated in her becoming a professional Chef.
Rob and Vikki, always being interested in coffee as a drink, were amazed to find a really outstanding and mature coffee “scene” in Australia, with some of the most knowledgable people on the doorstep. After discussing between themselves, Rob made the decision to study the subject of coffee making in depth, and looked around for a suitable school/teacher.
It wasn’t long before the name of Tony Vitello popped up. Now Tony has been around coffee for all of his life and has an unsurpassed reputation as a teacher. Tony is a founder of the Australian Coffee Gang and his successful students are sought after for job placements.
Rob sought out Tony and was accepted on his course. By applying himself diligently, Rob soaked up all the information he could from the Coffee Gang teacher and practiced, practiced and practiced.
At the same time, Rob began a detailed background investigation into roasting proper and worked with some established artisan Roasters. It was here that Rob began to develop a love for the process of taking coffee from its raw state, and roasting it so as to extract its full potential in the cup.
Rob was invited to be the only Barista of choice at the Hyde Park event of Australia Day in 2010. Rob served over 7 kilos of coffee between 7am till 2pm on that day.
Robs professional skills continued to be noted, and in February, one month later, he was invited to be barista at TAFF College and powerhouse museum, serving the entire campus.
Moving on with life, a young family, external circumstances dictated that a return to the U.K. was required. Heartbreaking as it was in leaving their beloved Sydney, Rob and Vikki sold the profitable coffee van business. Rob threw himself into intensive final training and knowledge gathering regarding roasting and all things production.
Upon their return to the U.K. The Hodge family ordered a professional Coffee Roasting machine and set up RAVE coffee immediately. Buying best green coffee from reputable sources only, they worked night and day to produce the Roast profiles for each varietal that Rob had worked so hard on. Working to a strict business plan, and roasting ONLY to orders for best freshness… and working with the worlds leading online purchase company, RAVE coffee has become one, if not THE most noted artisan coffee roasters the UK today.
When you buy a bag of coffee from RAVE, you have the collective knowledge and experience from coffee masters all over the world. No piece of information has ever been discarded by Rob, and only integrated into his practice when he has tested it for himself. Buy RAVE. Taste the difference.
Rave Coffee, Unit 7, Stirling Works, Love Lane, Cirencester, GL7 1YG
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