Degree of Roast.docx

1、Degree of RoastDegree of Roast, Temperature, DescriptionThis 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 r

2、oasts and what look,color,bean sizeandsurfacetexture,corresponds to the degree of roast. *(see note from home roaster George Steinert below).Roasting is more about exceptions than rules. I havethis pageabout bean color vs. ground coffee color that might be helpful. So get to it.(click on preview for

3、 full size image)Note: The above image is not the exact same beans pictured below. The gray strips on either side of this image are a photographic 18% gray card.1. Green unroasted coffee 0:00 - 75 fThis is a wet processed, Central American coffee, a accidental blend I have had sitting around. Each p

4、hoto here are different coffee seeds from the batch I roasted sosize and shape will varyseed to seed.Click on image for large photo, orherefor multi-bean photo2. Starting to pale4:00 - 270 fDrum roasters take a long time to transfer heat to coffee so there is little change in the first few minutes.

5、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 c

6、ultivar or Mundo Novo.Click on image for large photo, orherefor multi-bean photo3. Early yellow stage6:00 - 327 fAt 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 o

7、f 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.Click on image for large photo, orherefor multi-bean photo4. Yellow-Tan stage6:30 - 345 fThe roast is starting to as

8、sume 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 Cos

9、ta Rican and Mexican coffees.Click on image for large photo, orherefor multi-bean photo5. Light Brown stage8:00 - 370 fFirst 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.Click

10、on image for large photo, orherefor multi-bean photo6. Brown Stage9:00 - 393 fNow 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

11、 is responsible for browning of cooked beef!)Click on image for large photo, orherefor multi-bean photo7. 1st crack begins9:20 - 401 fAt 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 Cra

12、ck, which has a shallower sound, more like a snap). At the point of first crack the internal bean temperature would be around 356 f.Click on image for large photo, orherefor multi-bean photo8. 1st crack under way10:00 - 415 fAs first crack continues the coffee still appears mottled and uneven in col

13、or. 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 hea

14、t 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 t

15、o this window of temperatures when caramelization begins.Click on image for large photo, orherefor multi-bean photo9. 1st crack finishes10:40 - 426 fThis is considered aCity Roast. First crack is done and the roast is stopped.Notice the bean surface is smoother somewhat from expansion but still has

16、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.Click on image for large photo, orherefor multi-bean photo10.City+ roast11:05 435fCity+ means the coffee has cleared first crack, and time

17、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 che

18、mically 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.Click on image for large photo, orherefor multi-bean photo. Check here for thewhole bean vs. ground coffee comparison photosor aMacro pho

19、tos of a single City + bean.11.Full City roast11:30 - 444 fOn the verge of 2nd crackThis 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 she

20、en 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 a

21、s 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 s

22、ize 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.Click on image for large photo, orherefor multi-bean photoCheck here for thewhole bean vs. ground coffee comparison photosor aMacro photo of

23、a single Full City bean12.Full City+ roast11:50 - 454 fFirst audible snaps of 2nd crackThe 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 c

24、alled 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,

25、 more small cracks on the face (or flat side) of the bean.Click on image for large photo, orherefor multi-bean photo ora Macro photo of a single Full City + bean13.Vienna - Light French roast12:15 - 465 f2nd crackis under way(This is mydarkestespresso roast)The Vienna stage (also called Continental)

26、 to Light French stage is where you begin to findOrigin Charactereclipsed byRoast 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 c

27、arbony 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 general

28、ly a Light French Roast or a tad darker.Click on image for large photo, orherefor multi-bean photo.Check here for thewhole bean vs. ground coffee comparison photosor amacro photo of a single French roast bean.14.Full French roast12:40 - 474 f2nd crackis very rapid, nearing its end.Sugars are heavily

29、 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

30、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 thats my limit.Notice how fast and dramatic the change is from the previous photo - all that happened in less than 30 seconds!Click on image for large photo, orherefor multi-bean

31、photo15. Fully carbonized13:00 - 486 fSome call this Italian or Spanish roast, an insult to either!At this stage, the coffee can be over 25% ash; it is carbonized, dead, charcoal.Click on image for large photo, orherefor multi-bean photo16. Imminent fire .13:30 - 497 fThis bean is right at the verge

32、 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 forcafe 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 coffe