Troubles with various roasts and gassing of beans

[HMZimelka]

Hi all.

First post here...

I'm having some issues that have completely stumped me.

I've started to roast with a Diedrich IR2,5 at work and at home I have a Gene Cafe...
I've been roasting for about a year with the Gene Cafe, and only recently started with the IR2,5.

However, about 2 weeks ago, things have been getting strange, as the beans I roast started behaving different from what I am used to.

I actually have no idea where to start, as I'm simply too frustrated to think straight right now... LOL


I usually roast a City+ profile, for espresso based drinks. I use a Expobar Office Lever (E61) at home and at work I use a Faema Ambassador 2 group.
Standard procedure for me was to let beans gas for about 3 to 5 days according to the bean type and roast profile. Usually, this was enough to pull a rich tasting, smooth crema espresso or ristretto.

It feels, that overnight, things have turned upside down, and roasts I made on both my Gene and the Diedrich on the 29th of May are still giving off gas...
The shots I pull, on both machines, are full of bubbles, the crema is lighter than usual, and the taste is terribly sour.
Pulling shots with a bottomless portafilter, one can see beard filled with big bubbles.

The various batches of roasted beans from the 29th of May, across 3 different bean origins (Guatemala Antigua, Indonesia Mandheling, and also Columbia Excelso) all behave in a similar fashion.
They all are tasting horrid.

The only way to get a slightly better tasting coffee, which still isn't nice by any standard, is by grinding finer and extracting for longer. However, crema is thick, full of bubbles, and simply collapses, and my flat whites are ending up blotchy.

Both machines are maintained and cleaned properly. My machine at home especially.
I have changed nothing that I would consider obvious. The pressure and temperature of both machines are in order.
There have been no drastic environmental changes that I know of. It's just been getting very dry and cold here in Namibia over last couple of months.

The altitude is around 1600 meters, and its quite dry here. I have noticed, that since moving up from Cape Town last year, at sea level, that gassing times have been a little longer... but 10 days? Something feels wrong...

For those that have more experience than me, is there anything you recommend I could try, and do differently? I'm stumped

Thanks in advance!

Best,

Martin

 

[eldub]

I don't think it's a degassing issue.

It sounds like your current roasts are lighter than previous attempts, thus the sour taste and lighter crema..

Btw, what is a "flat white?"

 

[expat]

HMZ, I'm not a barista so I can't help you there but it seems you're having the same problems with two different roasters and two different coffee makers. If I read correctly you've roasted and produced finished coffee successfully on this equipment in the recent past - even tho the Deitrich is fairly new to you.

If that's the case it seems the only other variable is the bean or beans. Have you recently gotten in a new shipment of one or more of the beans you use?

 

[John P]

It's altitude and lack of humidity.

Here in Salt Lake City, we are at 1300 meters and have the second driest climate, after Nevada, in the States.

Typically I wait 7 days before using espresso after roasting, and I would say peak days are more like day 11-12.

Also, you will need to adjust your roast profiles. Normal altitude profiles do not work the same at high altitude. Adjust.

 

[HMZimelka]

Hi,

Thanks for your time replying!

The shots I'm pulling are improving, which does lend me to believe its a gassing issue caused by some environmental factors that I haven't had to deal with before.

I don't think it's a degassing issue.

It sounds like your current roasts are lighter than previous attempts, thus the sour taste and lighter crema..

Btw, what is a "flat white?"

I'm certain that the roasts are identical. I dump the beans right at the start of second crack, which sometimes varies by a few seconds, but not more.

The beans, even at day 10, were simply behaving like beans that were used directly after roasting. Sour, light, full of bubbles, and crema that just collapses after a few seconds.

A flat white is an espresso based drink, using finely textured milk foam poured over a single or a double ristretto shot, often accompanied by latte art.
Is it called differently where you are? See pic bellow.

HMZ, I'm not a barista so I can't help you there but it seems you're having the same problems with two different roasters and two different coffee makers. If I read correctly you've roasted and produced finished coffee successfully on this equipment in the recent past - even tho the Deitrich is fairly new to you.

If that's the case it seems the only other variable is the bean or beans. Have you recently gotten in a new shipment of one or more of the beans you use?

You are correctly understanding the situation, but the beans have not changed at all. I simply roast too little. I roast my own beans for home use, so 15kg of various beans I have at home will take me a while to get though (6 months I guess). At work, the Diedrich get used to roast for one restaurant/coffee shop, so consumption per day is still very low. Such a waste of a shite expensive roaster. Here, the local agents in South Africa sell the roaster for about US$ 21 000, which is a lot more than the $13 000 quote I got from Diedrich USA the other day...

It's altitude and lack of humidity.

Here in Salt Lake City, we are at 1300 meters and have the second driest climate, after Nevada, in the States.

Typically I wait 7 days before using espresso after roasting, and I would say peak days are more like day 11-12.

Also, you will need to adjust your roast profiles. Normal altitude profiles do not work the same at high altitude. Adjust.

OK, cool. Thank you! It's day 12 today for the batch in question. It is better, and shots are pouring out with far less bubbles than before... Still not where I want it though, but getting there slowly.

When you say I must adjust my roasting profiles, how exactly must I adjust? I've not read up on anything that resembles roasting at altitude, so I'll have to start looking.
I have done a few roasts which I stopped well into second crack, but those are not ready to drink yet. I usually prefer the the taste of beans roasted up to second crack, but not a fan of those roasted darker.

 

[eldub]

Btw... A good gauge of a roast level, ime, is the color of the crema as well as taste of the final product. The lighter the roast, the lighter the crema. An under roasted bean also tends to taste sour. I've experimented with many espresso blends less than a week after roasting that haven't tasted sour or shown badly as you describe above.

 

[HMZimelka]

The waiting has helped. Crema is a nice dark and smooth caramel colour, with no bubbles...
14-16 days after roasting...

 

[buckhorn_cortez]

I live in Albuquerque, NM at 1512 meters. We get 9-inches of precipitation in a good year. So far this year, we've had less than 1-inch of precipitation, and the daily humidity has been in the 5% range. I'm really not convinced that elevation and humidity have all that much affect on coffee roasting if you follow the recommendations of Diedrich for roast times with their equipment.

We roast on a Diedrich HR-1. With a Diedrich, you always need to adjust your profile so that you get the roast level you want in 15 minutes. Stephan Diedrich is adamant that the correct roast time on his machines is 15 minutes for any roast level. You adjust the profile to meet the 15 minute time. Are you achieving 15 minute roasts with the Diedrich? FWIW - The Diedrich facility is in Sandpoint, Idaho with an elevation of 649 meters.

To me, it sounds like you're under roasting the beans. I would suggest taking them all the way through first crack to second crack at a minimum. Joseph John (creator of Malabar Gold espresso) recommends 30 seconds into second crack for his espresso blend. He also recommends resting his coffee for 7-10 days before use.

We generally follow both Diedrich's recommendations for time and Joseph John's recommendations for roasting and resting espresso and have found that we have no problems with degassing the coffee and pulling excellent expresso shots.

Try roasting through first crack and slightly into second and then resting the beans for at least 7 days. Also, make sure your water is at 93 - 94.5 C at the group head. Cooler water temperatures will result in sour coffee. If you're less than 91.5 C - you're going to have sour coffee.

You may find out that the procedures you're using (flush time, etc.) at the new elevation have resulted in cooler water when you pull the shot.

 

[eldub]

I agree, buckhorn, but it doesn't sound like the op does.

I'be never noticed the crema get darker after beans are degassed a bit. To me, the roast level dictates the crema color as well as flavor profile, for the most part. When I pull samples at multiple roast levels, I'm usually determining just how far I have to go to get that batch of beans out of the sour, under-roasted zone.

 

[John P]

It's possible that the roast profile for the given beans is simply incorrect.

 

[eldub]

Thank you, John.

I think that's the most likely scenario.

 

[HMZimelka]

I live in Albuquerque, NM at 1512 meters. We get 9-inches of precipitation in a good year. So far this year, we've had less than 1-inch of precipitation, and the daily humidity has been in the 5% range. I'm really not convinced that elevation and humidity have all that much affect on coffee roasting if you follow the recommendations of Diedrich for roast times with their equipment.

We roast on a Diedrich HR-1. With a Diedrich, you always need to adjust your profile so that you get the roast level you want in 15 minutes. Stephan Diedrich is adamant that the correct roast time on his machines is 15 minutes for any roast level. You adjust the profile to meet the 15 minute time. Are you achieving 15 minute roasts with the Diedrich? FWIW - The Diedrich facility is in Sandpoint, Idaho with an elevation of 649 meters.

To me, it sounds like you're under roasting the beans. I would suggest taking them all the way through first crack to second crack at a minimum. Joseph John (creator of Malabar Gold espresso) recommends 30 seconds into second crack for his espresso blend. He also recommends resting his coffee for 7-10 days before use.

We generally follow both Diedrich's recommendations for time and Joseph John's recommendations for roasting and resting espresso and have found that we have no problems with degassing the coffee and pulling excellent expresso shots.

Try roasting through first crack and slightly into second and then resting the beans for at least 7 days. Also, make sure your water is at 93 - 94.5 C at the group head. Cooler water temperatures will result in sour coffee. If you're less than 91.5 C - you're going to have sour coffee.

You may find out that the procedures you're using (flush time, etc.) at the new elevation have resulted in cooler water when you pull the shot.

Thank you for your reply.
I've mentioned I usually roast a Full City at home, and have always enjoyed this roast level the most across the beans I've tried.
Every now and then, and especially during this recent issue, I roast a little darker. Usually up to about 30 seconds after the first sounds of second crack. The beans behave in a similar fashion as described, however, they reach their peak a little earlier.

On the Diedrich, my first crack is at 10:00, and at 13:30 I start to hear the first sounds of second crack, and I stop the roast at 14min.
My Gene needs longer, and usually I pull the beans at 15:00, but they behave in the same manner. (compared to the beginning of the year, they are also needing about 16 days) I will definitely try your recommendation, and I'll slow the roast down to achieve a 15min roast, but I have also read many people expecting first crack as early as 9:30. ??? seems early.

Here, the water boils at 94,2ºC here, so I do a cooling flush until the spluttering stops, and my brewing temperature usually is at around 94ºC. Luckily I have a thermometer probe to measure the temp. At work, the machine seem to brew at around 94,5ºC. I've already come to grips with the changes altitude has on my HX machine. I have also adjusted my boiler pressure accordingly.

I agree, buckhorn, but it doesn't sound like the op does.

I'be never noticed the crema get darker after beans are degassed a bit. To me, the roast level dictates the crema color as well as flavor profile, for the most part. When I pull samples at multiple roast levels, I'm usually determining just how far I have to go to get that batch of beans out of the sour, under-roasted zone.

I haven't changed my roasting profile and beans for home use from the beginning of the year (hot, humid) up to now (cold and dry). At the beginning of the year, I was happy with 7 days gassing, after which shots looked great. Now, I need to wait much longer to reach the same taste and look. It's a simple observation.

Yes, of course, roasting level dictates crema colour and taste profile, however, the roast needs to have reached it's peak before one can settle on the profile one wants.

Gassing beans, when ground, release a greater amount of gas due to the increase surface area. When hot water hits the grind, this reaction increases. During extraction, this gas release will cause an under extraction, making the crema lighter, causing earlier blonding, with more bubbles in crema. Plus, the taste is sour. To compensate, I grind finer, and extract longer, but I avoid drinking coffee like this.

With the Diedrich, my initial roast had first crack at 10:00, and the developing period was 3 minutes. Pulled at 13min.
My Gene needs longer, and usually I pull the beans at 15:00

After the said 16 days, the crema is very smooth and rich, and shows the colour I expect. At day 7-10, the crema is still a cake like mess.

 

[buckhorn_cortez]

I will definitely try your recommendation, and I'll slow the roast down to achieve a 15min roast, but I have also read many people expecting first crack as early as 9:30. ??? seems early.

The amount of time to reach 1st crack is variable depending upon the type of beans being roasted, and the roaster temperature when you drop the beans. Generally, with a Diedrich, you try to get the beans to "bottom out" (the roaster dropping in temperature from the bean mass) at 1.5 minutes after dropping the beans into the roaster.

Obviously, the higher the roaster temperature when you drop the beans, the higher the temperature the roaster will be when the temperature bottoms out, and then starts increasing - AND the shorter the time will be to first crack. You don't want the roaster to stall, so you want the temperature bottom extend only 15-30 seconds - depending upon the burner setting for the beginning of the roast profile.

Then you have how you apply heat for the profile (temperature vs. time). You can apply a lot of heat early in the roast and have an extremely steep time/temp slope, then reduce the heat and extend the ramp to 15 minutes at a very shallow time/temp slope.

Or, you can have a very shallow ramp at the beginning and finish with high heat and a steep ramp, or make the ramp even over the entire roast etc. There are problems with some of these approaches like the really steep ramp in the beginning with a lot of heat can cause blowouts in the beans from steam trying to escape. Conversely, a long slow ramp can cause the beans to heat too slowly and not start the maillard reactions when needed ending with beans that are underroasted internally with a grassy taste.

The idea being - you need to tailor the heat application over the time of the roast for the beans being roasted to arrive at the 15 minute mark at the roast level you desire.

The other thing you have to quantify for the Diedrich is the roaster response window. As an example, let's say there is a 3 minute window. This means that what you did 1.5 minutes ago (increase heat, decrease heat) will affect the roast now - and what you do now will affect the roast in 1.5 minutes = 3 minute window.

So, you always have to anticipate when and how to adjust the machine with the response window in mind and try and keep the heat at the level you want for the profile you're trying to achieve. With a manual machine, you have to do this with gas pressure (burner heat) and roasting drum air using manual adjustments of each.

I don't know how familiar you are with the Diedrich and the roasting air control - but, that is one of the major controls on that roaster for heat flow and temperature on the roaster along with the burner level. If you know the roaster, you know it can be adjusted 10% fresh air / 90% recirculated (10:90); 50:50;, and 90:10. That also changes the type of heat from radiated / IR to convection as you go through the air control.

My point is that you're not necessarily "slowing down the roast" - you're tailoring the heat and air circulation to reach the roast level at 15 minutes. You want to fully develop the beans to their optimum level.

If you use the tryer during roasting, you can watch the beans puff up and the surface get smooth as the roast develops. When the surface is smooth and not wrinkled at the end of a roast, you have ensured that the beans have been handled correctly with time/temperature as they have been expanded to their maximum.

If you already know all of this -- then what you need to do is just profile a couple of roasts of the same beans and pick the one you like best.

 

[expat]

There have been several comments in this thread about a 15 minute roast. Now I'm a new roaster, just at it for a couple of years, roasting in 10kg batches, and have only roasted a few thousand kilos of beans, but who determined that a 15 minute roast is optimum?

When we first started roasting The Lovely & Talented Roast Mistress and I were bound to the clock. We were time fanatics. But then we quickly figured out, at least for us, that time means nothing. So we put the timer away and just started roasting for (1) mainly smell and taste (yes, she takes beans from the tester and tastes them during the roast to determine greenness and state of development) and color and (2) appearance.

Buckhorn_Cortez said, "you're tailoring the heat and air circulation to reach the roast level at 15 minutes. You want to fully develop the beans to their optimum level."

If I'm getting his intent in that statement then I agree totally -- you're trying to roast in 15 minutes regardless of the beans. And like people beans are different. And every day you roast is different -- more or less humidity, hotter or colder, etc., and these all seem to affect roast times. For us here in cool to cold, and usually wet Ireland our Colombian develops at a much lower roaster temp than say our Ethiopian Sidamo does.

So it seems you've solved your degassing issue by letting the beans rest for 2+ weeks but as to roasting itself maybe forget about the clock and focus on the bean. I know Mr. Deitrich has A LOT more experience that I'll probably ever have but if he is firm about 15 minutes regardless of bean then I've got to disagree (although I've really got to think that he's just been misunderstood or misquoted). And if we're wrong and 15 minutes is the standard then I don't see us changing. I can't argue with the testimonials on our website's testimonial page so for us, even a 23 minute roast seems to be working.

I'd like to hear what some of you have to say about this. Is 15 gospel or just something that got misunderstood along the way?

 

[buckhorn_cortez]

There have been several comments in this thread about a 15 minute roast. Now I'm a new roaster, just at it for a couple of years, roasting in 10kg batches, and have only roasted a few thousand kilos of beans, but who determined that a 15 minute roast is optimum?

This is what Stephan Diedrich recommends for Diedrich built roasters based upon his experience with his roasters. The OP was using a Diedrich roaster so I thought the information was germane to the conversation.

We have found this recommendation works for the Diedrich roaster we use, and have roasted several thousand roasts through it of various types of beans. How you develop the roast within this time window is a totally different subject. For a general, even roast we would try for a heat rise of 22-24 degrees F per minute heat rise. This is with a bottom out temperature of 230F. If you bottom out at a lower or higher temperature, then you have to adjust the remainder of the heat rise for that temperature. That is how you control the heat application and profile is adjusting the drum temperature when the beans are dropped and then adjusting the heat rise per minute for the bean type and bottom out temperature for the desired end roast level for the remainder of the roast.

If you do it differently, that is, different roast times for different beans and you get good roasts - fine. No one is keeping score, there will be no fines levied, the government won't be coming in to audit you, etc. The idea is to get a good roast.

We find the fixed 15 minute time window to be how we like to work with the machnine by adjusting drop temperature, bottom out point, and time versus temperature heat rise for the remainder of the roasting time.

When we first started roasting The Lovely & Talented Roast Mistress and I were bound to the clock. We were time fanatics. But then we quickly figured out, at least for us, that time means nothing. So we put the timer away and just started roasting for (1) mainly smell and taste (yes, she takes beans from the tester and tastes them during the roast to determine greenness and state of development) and color and (2) appearance.

We go by first time to first crack, first crack temperature, and how long that stage lasts combined with samples pulled from the roast as the beans start to turn brown. Of course, roast development is dfferent for each bean type. We document the roast with roasting notes for every bean type and a complete roasting log that is reviewed prior to roasting a new type of coffee as a starting point.

Buckhorn_Cortez said, "you're tailoring the heat and air circulation to reach the roast level at 15 minutes. You want to fully develop the beans to their optimum level."

If I'm getting his intent in that statement then I agree totally -- you're trying to roast in 15 minutes regardless of the beans. And like people beans are different. And every day you roast is different -- more or less humidity, hotter or colder, etc., and these all seem to affect roast times. For us here in cool to cold, and usually wet Ireland our Colombian develops at a much lower roaster temp than say our Ethiopian Sidamo does.

That's why we keep roasting logs for every single roast, so that every day isn't a new day. We can interpolate changes that may need to be made for the same bean type roasted on a different day as the starting conditions are different. In a perfect setup, you would temperature and humidity control the bean storage area and the roasting area - we don't have that luxury so we document ambient conditions to identify how to make changes in the roast without the adjustment being a total, off-the-top-of-your-head SWAG.

So it seems you've solved your degassing issue by letting the beans rest for 2+ weeks but as to roasting itself maybe forget about the clock and focus on the bean. I know Mr. Deitrich has A LOT more experience that I'll probably ever have but if he is firm about 15 minutes regardless of bean then I've got to disagree (although I've really got to think that he's just been misunderstood or misquoted).

I assure you, neither I nor my wife misunderstood Stephan Diedrich's insistance on a fixed, 15 minute roast time when we attended his roasting class. In fact, the book given to you as part of the class has that recommendation in it.

And if we're wrong and 15 minutes is the standard then I don't see us changing. I can't argue with the testimonials on our websites testimonial page so for us, even a 23 minute roast seems to be working.

I'd like to hear what some of you have to say about this. Is 15 gospel or just something that got misunderstood along the way?

There is no "right or wrong" - there are only poorly roasted beans and well roasted beans - nothing else counts. As I've state earlier - roast however you want. Diedrich's recommendation is for his roasters and if you understand how to adjust the roasts within that fixed roasting time - it works. If you want to develop your own roasting methods - that's up to you. I'm sure you can find people with the same amount of experience as Stephan Diedrich who are diametrically opposed to his recommendation for a fixed roasting time and also roast excellent coffee.

The one thing the fixed roasting time, and adjusting the roasting profile within that time window, does is take one variable out of the process - total roast time.

If you feel you that a fixed roast time is a constraint on your personal technique - I don't think anyone one else cares. If you get a good roast as the end product - that's all that counts.

Let me state this one more time - the reason I brought this up is that the OP is using a Diedrich roaster and I think it is a valid point of discussion as it addresses a manufacturer's recommendation for a specific piece of equipment.