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02/27/2021 9:50 AM
Questions are best asked in the forum. The posts will last longer, and will be seen the most by members. After a few more posts in the Shoutbox, the post you made will no longer be seen.... maybe you could also introduce yourself and share a little.

02/27/2021 9:29 AM
I'm looking to hire someone to teach/help me to find the best roast profile for the 3 types of coffee that grow on my farm in nicaragua. I live in LA, but but could go anywhere in so cal with my Behmor for a roasting lesson. Please contact me if you're in

02/17/2021 7:20 PM
When your wife thinks 30 grams for a 6 cup setting is strong, you learn to drink muddy water when you are making coffee for both of you.

02/17/2021 8:32 AM
I use a rule of thumb of 60 grams per liter. 8 cups (1 liter, 32 oz) = 60 grams, 6 cups (3/4 liter, 24 oz) = 45 grams. 10 cups = 75 grams 12 cups = 90 grams

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OldMan41, depends what is "a pot"... usually is more accurate to specify the brew ratio, instead grams of coffee. The most usual is 1:15, thus 40 grams for 600 ml of water. If the 100 grams are for one liter pot, then we are talking about 1:10 ratio.

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1C Variation
ChicagoJohn
Most of the beans I've been working with up until now have had 1C in the range of 193-195C (~381F). Today, for the first time, I tried a Kenya Kigutha AA sample from Happy Mug using my newest popper mod. They recommend being careful not to exceed 1C.

What I noticed is that this sample 1C started at 185-186C (~366F) and it had a very healthy degree of 1C within a few degrees higher. So I adjusted the development time accordingly. Is this typical of Kenya coffees? And what would account for a 10C / 18F temperature in 1C?? Moisture?

Being new to all this, I was just surprised to see this low a 1C.

Profile attached.
ChicagoJohn attached the following image:
kenya-kigutha-aa.jpg

So many beans; so little time....
ginny
John:

ya no all else being equal or about the same there is no question for me that it as you said:

Quote

Moisture?



I have always found that many of my Africans hit 1st crack soon after 370 in my Hot Top 2K


that particular bean is really nice.


ginny



edit to correct temp

beach
Edited by ginny on 08/19/2015 4:38 PM
ChicagoJohn

Quote

ginny wrote:

John:

ya no all else being equal or about the same there is no question for me that it as you said:

Quote

Moisture?



I have always found that many of my Africns hit 1st crack soon after 180 in my Hot Top 2K


that particular bean is really nice.


ginny

beach


Thanks, ginny. Being so new to this, I just haven't seen 1C go this low. Thanks for the input. Can't wait to taste this one... but I will ... forum.homeroasters.org/images/smiley/shock.gif

postscript... thanks for the tip on Happy Mug; I really like them. forum.homeroasters.org/images/smiley/greenman.gif
So many beans; so little time....
JackH
I find 1C at about 380F too for a lot of coffees. Some do start a bit early or late but usually around 380F on my roaster.

I think with the Kenyan, not exceeding 2C should be the case. Maybe a typo.
---Jack

KKTO Roaster.
ChicagoJohn

Quote

JackH wrote:

I find 1C at about 380F too for a lot of coffees. Some do start a bit early or late but usually around 380F on my roaster.

I think with the Kenyan, not exceeding 2C should be the case. Maybe a typo.


Thanks so much for your input, Jack. I sincerely appreciate it. But 380F would amount to 193C in my jargon is exactly what I'm used to seeing, and this one was quite a bit lower at 367F / 186C.

If, indeed, moisture levels explain this, the question that would remain is whether one should then go by 1C or by temperature? At this point in my coffee journey, I am not entirely sure about what causes the first crack. I am guessing it is much more than moisture because if I take beans up to 120C an hold them there for a hour, they should be thoroughly dried out, but they still hit first crack at about the same temperature they would otherwise.

So I'm thinking there are chemical phenomena happening, exothermic phenomena (whereas evolution of moisture is highly endothermic), that may be involved. Hence I guess I am not still fully comfortable I understand why these Kenya beans went into first crack almost 18 degrees F lower than most of the other beans I've roasted.

Secondly, Happy Mug suggested not to exceed 1C by more than 25 seconds. So Not exceeding 1C was basically what they suggested. It was not a typo as "not to exceed 2nd crack." They were basically saying to make this a very light roast, which, according to the time-temperature log I attached, I think I probably did.

Lot's to learn about here, and I really, really do appreciate getting feedback from folks like you who have so much more experience !! Thanks !!

forum.homeroasters.org/images/smiley/drinking-smiley05.gif
So many beans; so little time....
ginny
John, I corrected my temp number I meant 370...


ginny
ChicagoJohn

Quote

ginny wrote:

John, I corrected my temp number I meant 370...


ginny


Thanks, ginny!

So I decided, in the interest of science, to go back out with my new roller roaster, very easy to do now, and try an experiment to see whether moisture is playing a role in the lower 1C temperature.

I present, below two time-temperature profiles. The first is the one I submitted previously and the second is the new one with significant time added for drying of the beans to occur, especially since they are floating around in hot air (as most of us are here in the US these days with our politics :)

You will note that although water should be evaporating above 100C, the additional time-temperature above 100C had virtuall no difference upon 1C.

While we cannot reach definitive conclusions on the basis of a single experiment, I think it safe to say we cannot dismiss the lower 1C temperatures of this Kenya bean as simply due to moisture content, at least not on the basis of my experiment.
ChicagoJohn attached the following image:
kenya-drying-interfal.jpg

So many beans; so little time....
HoldTheOnions
I had a kenye kianje AA that would sometimes give me odd 1c times, although they were late, not early, but maybe kenyans are odd that way.

Another thought, if the beans stop moving for even a second or two on the poplite, then you will likely get 1c early. The primary reason I upgraded my blower was to eliminate problems associated with that.
ChicagoJohn

Quote

HoldTheOnions wrote:

I had a kenye kianje AA that would sometimes give me odd 1c times, although they were late, not early, but maybe kenyans are odd that way.

Another thought, if the beans stop moving for even a second or two on the poplite, then you will likely get 1c early. The primary reason I upgraded my blower was to eliminate problems associated with that.


That's a good thought about the motion of the beans, HoldTheOnions, but with the funnel mod at 60 degree angle and the juiced up blower power, I have never had that issue happen. I'll repost the comparison I did in "drying out time", and you will note that the 1C was the same for both; and I have consistently seen very close replication of 1C within samples for everything I've roasted thus far. So I believe that these beans do have a significantly lower 1C threshold temperature; whatever chemistry is responsible for that outgassing and the associated exotherm. At the same time, I have no doubt about the validity of your thought and observation regarding the potential effects of suboptimal motion in a popcorn popper where we want convection to be the mode that dominates heat transfer to individual beans uniformly.

I couldn't wait to try these two profiles so I did this morning. The first one with the shorter time was excellent with a bright citrus acidity but with good body and overall "balance". I'm so new to this that I'm not comfortable trying to articulate my experience, but I will say that of all the single origin samples I've tried, probably 15 or so, this Kenya roasted like this gives the best brightness yet overall balance of anything I've tried thus far. I love it.

One thing I noticed in the second sample that had more "drying time" was in my hand grinder. I have noticed rather obvious differences in uniformity of torque versus degree of variation and in average torque; both are associated with the compressive strength of individual beans. Longer roasts into or just before 2C produce beans that are much more uniform and requiring lower average torque.

The first sample, like other light roasts I've done, had quite a lot of "hard" beans that took significantly more torque to crush. The second sample had very few if any and required less torque on average.

The second sample also seemed to have a little less brightness, but with my lack of experience, this could have been my perception rather than a true difference in the coffee. However, I liked the overall balance a little better in the second one -- it was still a nice, broad spectrum but the bright end seemed a bit more muted.

I'm saving the balance of both for another trial next week to see how they fare then.

Re-post of the two profiles:
ChicagoJohn attached the following image:
kenya-drying-interfal_1.jpg

Edited by ChicagoJohn on 08/20/2015 6:11 AM
So many beans; so little time....
ChicagoJohn
In considering why a Kenya AA has a significantly lower 1C temperature than other single origin samples I've tried, one possibility was higher moisture content. However, when I extended the time at drying temperatures by several minutes, no change in 1C temperature was observed.

I read several accounts of 1C in various articles on line and many stated that 1C was entirely endothermic (heat absorbing) and that the primary mechanism was pressure build up within the beans from steam. In a scientific paper, however, International Journal of Mass Spectrometry 365366 (2014) 324337 titled Evidence of different flavour formation dynamics by roasting coffeefrom different origins: On-line analysis with PTR-ToF-MS, the authors state, the following:

"During the initial endothermic phase of roasting, the green beans dry,reducing the water content from about 812% to a few percent.Further heating of the beans initiates the exothermic pyrolysis reac-tions. This can be perceived as a popping sound, called the first crack(at about 175185◦C). If one continues roasting to a very dark roastdegree, at higher temperatures (above 200◦C) the second crack can be heard."


I'm thinking that generation of steam could arise from both existing moisture levels in the beans, for which liberation would be an endothermic process, and from decomposition of carbohydrates such as sugars via caramelization (one type of pyrolysis) which could be exothermic under some circumstances. A disaccharide like sucrose should initially break down into glucose and fructose with evolution of water and then upon further condensation produce more water.

The diffusion of existing moisture within the beans outward to the surface would be accelerated by elevated temperature, but I would see this as a continuum of increasing rate with higher temperatures whereas my experience of 1C is that the temperature for a given sample of beans is quite repeatable.

Since evolution of significant additional water from decomposition of carbohydrates, for example, would be a chemical reaction that would probably involve a certain activation energy and a certain temperature threshold, I'm thinking that it, rather than existing bean moisture, is more likely cause of sudden increase of internal pressure that results in 1C.

Maybe, however, it takes more than a few minutes to thoroughly dry out the beans, so I'm considering an experiment where the beans are thoroughly dried and reach a constant weight at 140C, and comparing the onset and magnitude of 1C for that sample versus one that is not specially pre-dried. If both samples are roasted to the same time-temperature profile, it might also be interesting to see whether there is any noticeable difference in taste.

If someone has already done this experiment, let me know. I'm just curious because I've read a number of contradictory things about 1C on line.
So many beans; so little time....
ChicagoJohn
Noting an unexpectedly low 1C temperature for some Kenya AA beans, moisture was suggested as a possible cause. In some internet research, some were suggesting that 1C was an endothermic process solely due to steam and others that it was an exothermic process involving condensation reactions within the bean.

I did a simple study hoping to better understand this. I weighed two samples of the Kenya beans at 91.0 gm. I put one sample in a 9 diameter aluminum cake pan in a table top convection oven set at 125C fitted with a double screen to minimize radiant heating and with a K thermocouple positioned directly above the beans. The cycling of the oven controller resulted in a continual cycle of 110C to 120C in the vicinity of the beans, with an average temperature of 115C.

As it was apparent that complete removal of water and any low molecular weight organic volatiles would require much longer than anticipated at this temperature, I decided to try to find a suitable curve fit that I could extrapolate to estimate the total volatile level. This was done with an inverse power function which provided a very good regression fit, and the value extrapolated out to 24 hours was about 10% of the initial bean weight. Since continuing the drying process for that period was impractical, I arbitrarily decided to terminate it at 90% of the total, 9% weight loss based upon the original weight.

I felt that at 90% of complete drying / removal of VOCs I would still be able to see the effect of drying upon 1C in terms of both onset temperature and magnitude of rolling crack. The relevant graphs are attached.

In comparing the dried beans with the original sample, no obvious difference in size was noted although the dried been color had shifted from green to yellow. The bulk density of the dried beans was a little lower at 0.67 gm/cc versus 0.70 gm/cc for the green beens.

Following similar roasting profiles for both samples, I observed that for the green beens, 1C was at 187C/369F but that the onset temperature increased to 195C/383F for the dried sample. Rolling 1C for the green beans was in the interval 189-200C versus 196-204C for the dried sample.

These results are consistent with the hypothesis that higher volatiles (moisture plus perhaps some organics) can lower the onset temperature of 1C; my initial question. I did not use the chaff collector for this experiment, and I observed that for both samples profuse chaff was emitted starting around 180C/356F, suggesting that drying did not have a large effect upon that process.

However, the fact that a significant rolling 1C was still observed for the 90% dried sample, though at a higher temperature, suggests that there is more to 1C than merely release of moisture, which had been reduced by 90%. I continue to believe it is likely that condensation reactions such as dehydration of sugars and other carbohydrates, also play a significant role in 1C.
Apparently, as I have read, pressures build up within the bean until burst strength is exceeded, and drying would perhaps tend to both reduce the volatile content and also increase burst strength of the bean by reducing the plasticizing effects of water and other lower molecular weight volatiles.

An unexpected observation was what appears to be a slightly larger roasted bean size in the dried sample. I checked the bulk density of the two final roast samples and it was a little lower for the dried sample which would be consistent with larger beans and greater interstitial space; 0.34 gm/cc for dried versus 0.37 for green after roasting; both roughly half the bulk densities before roasting.

Im planning to let these rest for a few days and then see if I can notice any differences in the cup.
ChicagoJohn attached the following images:
dried-v-green-time-temperature.jpg roasted.jpg color-before-and-after-drying.jpg extrapolated-wt-loss.jpg incremental-drying.jpg

So many beans; so little time....
ChicagoJohn
Forgot to mention -- Final roast yields based upon 91 gm were 86% for the green beans and 85% for the dried sample, suggesting that for the most part the 9% initial loss in drying was part of what occurred in the green sample during the roast.
So many beans; so little time....
ChicagoJohn
I tried the dried coffee roast this morning, and I'd say it differs in the same way as the profile where I extended the "drying time", only more so. It was drinkable but lacked the low-end, bright, citrus component.

From further investigation on the internet, it seems that the recommended moisture range for storage is 10 - 12%, and from the extrapolation of my measurements, this Kenya AA was just over 10%, the recommended minimum.

I was unable to find anything about taste effects of reducing moisture significantly before roasting (in this case down to 1%), but from the low rate of diffusion I saw at 115C, and the change in 1C onset of 8C or 15F associated with moisture level differences, it appears there is still significant water present at 1C when starting out with 10%. It is likely that this water level is a factor in the various reactions forming carboxylic acids, aldehydes, and ketones that affect aroma.

While all three profile results are drinkable, I prefer the first one using the standard "light roast" profile I usually use.
So many beans; so little time....
kaffeine
ChicagoJohn,

This post was quite interesting to read. I am a returning student studying civil engineering, and to me your scientific approach is impressive to say the least!

So let me kick some rocks around, as we civi's do sometimes... As I was researching beans I read somewhere that some beans tend to be "hard shell" thus requiring more heat to crack. So could it be that these Kenya beans are "thin shell", requiring less heat to crack?

I cannot recall where I read about bean hardness, so I've got no reference leg to stand on. But I thought I'd throw this out there as a possible research avenue...

... Ok, back to my homework.
ChicagoJohn

Quote

kaffeine wrote:

As I was researching beans I read somewhere that some beans tend to be "hard shell" thus requiring more heat to crack. So could it be that these Kenya beans are "thin shell", requiring less heat to crack?
.


I've also read about differences in bean structure / integrity, and you raise an interesting question at how these differences would affect first crack onset temperature. I've seen some micrographs how the distinction is evident in degree of porosity, especially as it occurs around the center "strip" where I imagine the two beans were attached at one time. I'll try to get some soft beans just to see how they act. I think I may have read that some robusta's are in this category.

I'm pretty sure the Kenya beans I'm using are in the hard-bean category, and their moisture content is at the low end of what I've read is acceptable for storage - 10 - 12 or 13%. These are 10%. But, as you saw, reducing that level significantly does elevated the 1C onset temperature (and adversely affects my subject assessment of taste.)

Thanks for commenting and best wishes for your career.
So many beans; so little time....
ChicagoJohn
Two additional observations:

I tried drying 104.3 gm of the Kenya AA beans in a food dryer turned up to 145F maximum temperature. I measured the temperature at 60C, 140F. I left them in there overnight and recorded the weight loss at 6.9% the following day. After 24 hr exposure to ambient conditions, their weight had not changed (but we use a dehumidifier).

So I put a couple of damp paper towels in a larger bowl and exposed them to this environment covered (~ 100 RH). After a week at these conditions, the weight was 0.75% higher than it had started out. Not sure where the equilibrium moisture contend at ambient conditions would have ended up because I roasted them this morning, and 1C was back at 187C again.

I had a sample of Brazilian dry process from Sweet Marias, so I decided to try that and was amazed at a 1C of 203C. Never had one that high before, and I'm thinking it may be a result of the dry process used. End of 1C was 215C where I stopped the roast (2 min after 1C started). I am pretty sure I heard a little 2C happening towards the end.

Sweet Maria's recommendation was City+ to Full City, so I'm thinking that is probably what happened as a result of the temperatures involved.
So many beans; so little time....
JETROASTER
Many thanks for sharing your research.
The carbohydrate/sucrose breakdown theory makes a lot of sense. The timing of it is in line, and the more intense 1C for the more structurally sound beans dovetails nicely.
I think your drying experiments effectively ruled out free moisture as a player.
The experiments also seemed to demonstrate the varied loss of other VOCs from different drying process. This part still vexes me....
How could those same VOCs ever remain in roasted coffee...regardless of the drying process?
In structurally dense beans, is time more of a factor?
The Mass Spectrometry research experiment seemed to suggest that the release of some volatiles occurred later with the old root stock Africans than with the more modern beans.
Is there a relationship to bean structure, or did the old school African bean (I think it was an Ethiopian) simply have fewer VOCs to begin with?
Again, many thanks for sharing your insights.
Cheers, Scott
Ringo
Great write up, I really enjoyed reading. I will kick one rock also. I have noticed if I come into 1st crack too slow I will get a silent crack. I have always guessed that if pressures build too slow they can leak out and not crack the out sides. I took the Boot roasting class and one of the road maps to the roast is a chemical smell coming out of the beans right before 1st crack. A few seconds after the smell you will get 1st crack. You have to pull the beans out with a tryer to get this smell. Boot teaches that this is a better roasting road map then 1st crack.
On a side note after I got a better RTD for my roaster with faster reaction time I have very little variation in 1st crack temp given a charge size. For me 1st crack will be 402 to 407f.
Edited by Ringo on 09/01/2015 5:00 AM
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
ChicagoJohn

Quote

Ringo wrote:

Great write up, I really enjoyed reading. I will kick one rock also. I have noticed if I come into 1st crack too slow I will get a silent crack. I have always guessed that if pressures build too slow they can leak out and not crack the out sides. I took the Boot roasting class and one of the road maps to the roast is a chemical smell coming out of the beans right before 1st crack. A few seconds after the smell you will get 1st crack. You have to pull the beans out with a tryer to get this smell. Boot teaches that this is a better roasting road map then 1st crack.
On a side note after I got a better RTD for my roaster with faster reaction time I have very little variation in 1st crack temp given a charge size. For me 1st crack will be 402 to 407f.


Thanks for the comments, Ringo, they were very helpful to me in thinking about this further. What you say regarding the odor emission makes a lot of sense to me. With a popper mod, I have definitely noticed this phenomenon but have not previously tried to link it to incidence of 1C. I will now begin doing that, recording observations. My hypothesis is that both residual moisture and water coming from condensation reactions (which would emit odors) contribute to the internal pressure, and some beans may also have higher integrity withstanding higher pressures before they crack, (explaining while the beans in a batch don't all crack at once.)

While I have not observed an effect on 1C onset temperature from length of interval approaching 1C, your observation certainly makes sense and may be bean sample specific; i.e., it may not be equally evident in all varieties or samples within them; and roasting method specific.

I use a K type thermocouple rather than an RTD, and I have two modified roasters. I note very reproducible 1C onset temperatures within a given 1 lb sample, replicated for both roasters -- within a degree every time. I also have observed large differences among coffee types; e.g., Kenya AA, Ethiopian Yirga Cheffe, and most recently Brazil Dry Processed; at 187C, 195C, and 203C, respectively.

An analysis of variance of these data would show a very high level of statistical significance for inter-type differences with bean type accounting for a very large percentage of total variance, and there would likely not be a significant effect due to which of the two roasters I use. I roast five 91 gm batches per pound received, and I've picked up quite a few different types of beans, and the pattern of variance in 1C onset temp within each sample has been surprisingly repeatable.

The temperatures you report correspond to 206C - 208C. I've not yet seen a 1C onset that high, and in most cases I've finished 1C and am terminating the roast before 206C (I prefer light roasts). The range I've seen, 187-203C, repeatable to 1 degree C, would correspond to be 369 - 397F.

So, it seems that differences in roasting methods (e.g., small batch air-popper versus drum roaster) may significantly affect measurement of 1C onset, and perhaps even observed differences for various bean types. The important thing would seem to be ability to control so as to achieve repeatability within a given roasting set up from batch to batch.

Again, thank you for your thoughtful comments. As a total newbie to this area, I'm trying to formulate a general theory to help me know when things are following an expected path and, more importantly, when they're not, and hearing about others' observations is a huge help for me in making sense of my own.
Edited by ChicagoJohn on 09/01/2015 6:42 AM
So many beans; so little time....
Ringo
I need to clear on thing up I do not run RTDs I run TC. For my environmental temp I use a bare wire TC for fast reaction time and for the bean temp I use a very thin cased Tc. I run RTDs with my day job and work jargon crossed into coffee jargon. RTDs would be better but my PID will not read them. I am very interested in seeing where you take this research. The better we understand what is happening in a roast the better our product will be.
All you need in life is ignorance and confidence, and then success is sure. Mark Twain
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