What does coffee taste like when you use too much airflow?

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
Ziv Sade
Posts: 58
Joined: 11 years ago

#1: Post by Ziv Sade »

Hi all,

Lately I've been playing with higher then usual airflow levels. I am doing it because I found out that on my roaster (huky 500) when I use lower airflow - there is a chaff build up on the exhaust pipe and also chaff is falling from the front of the drum plate, so I decided to give it a try - Roasting with a higher airflow.

The thing is - I have noticed a sour taste in my coffee and I am also wondering if my beans will age much quicker that way like they usually do on an air roaster.

I would love to hear your thoughts regarding the above.

Thanks in advance.

Ziv Sade (original poster)
Posts: 58
Joined: 11 years ago

#2: Post by Ziv Sade (original poster) »

Someone???

HoldTheOnions
Posts: 764
Joined: 9 years ago

#3: Post by HoldTheOnions »

I have air roaster, and I know that same temp reading at a low fan speed is not the same as on a high fan speed. So if you are raising your fan speeds, then you would need to increase your temps for consistency with previous roasts. That said, changing the fan speed could also have other implications, such as changing the rate at which beans dry and accordingly how the bean mass changes during the roast. So even if you compensate for the increased fan speed with a higher temp, your roast could still come off differently. Do you log your bean temp curves? If so, then you should be able to back into it. If not, then it may take a little more work to get back to where you were. I would methodically raise fan speed a little bit at a time, then play with temps until I was happy, then keep doing it until I was at desired fan speed. I'm just thinking you would have easier time make several little jumps vs. one big one. Maybe someone else has better advice.

dustin360
Posts: 825
Joined: 13 years ago

#4: Post by dustin360 »

Why do you think fluid bed roasted coffee ages faster?

Also more airflow just cooks the bean more evenly, there isnt anything magic that it does. So the bean with have less variation from inside to outside. I often aim for a degree of variation between the inside and outside of the bean, so I rarely roast with max airflow. But since every coffee is different, some will taste better with higher airflow and others will not.

beanfish
Posts: 20
Joined: 9 years ago

#5: Post by beanfish »

OK, I'm roasting on a Huky 500 (original configuration), also.

1. When charging the Huky, lean it back to make sure the beans don't lodge int the exhaust.

2. Roast with the trier upside down (open side facing downwards). To prevent spillage, only partially withdraw the trier during roasting.

3. The chaff problem seems to occur more frequently when using the baffle. Leave this is full open position and use a speed control on the DC motor
instead to control airflow.

4. The least expensive speed controls are sliding switch fan dimmers (< $12 http://bit.ly/1vH5Bc1 ; < $30
http://http://bit.ly/1ATDpsJ ). Great, but two caveats: Firstly they don't have a long movement, making
find adjustments a little fussy-- possible, but fussy. Stick some light colored tape alongside the slide and mark it incrementally to aid in consistency.
More expensive fan controls like this one are better, and the best, arguably, is a variac like this one.

IMPORTANT NOTE: As far as I'm able to tell, of the several types of thermocouple available, those supplied by Mr. Li appear to be the ungrounded
type. This means that if you are using a fan dimmer instead of a variac (http://bit.ly/17V2ng1, you might wish to
ground the Huky itself. The ungrounded
TCs read more quickly than grounded types, but they are subject to inaccurate readings if they are bumped or moved and thus
momentarily ground to the frame of the Huky. The result is crazy readouts. Again, just ground the Huky's frame to avoid this.

Lastly, again addressing the chaff issue, at the outset of 1C, where most of the chaff is released give the fan a blast to clear any clogs and then return it to normal operating range.

Scott Rao, in "The Roaster's Companion" suggests using a lighter to determine the baseline ventilation. Hold the lighter to the open trier hole and adjust the fan so that the flame leans toward the opening, but is not extinguished. Others I've read online suggest that at 1C the fan should be kicked up to about 75% while reducing heat after the endothermic flash (a very brief dip in temperature-- sometimes not even clearly detectable on the thermometer readout) that occurs shortly after the outset of 1c, just before the roast goes exothermic).

Hope some of this is along the lines of what you were looking for. I'm not super expert, but I pay attention, take careful notes, try and use as scientific approach as I can afford (no VST, though), and enjoy good coffee. :)

Mile High Roaster
Posts: 65
Joined: 10 years ago

#6: Post by Mile High Roaster »

Ziv Sade wrote:Hi all,

Lately I've been playing with higher then usual airflow levels. I am doing it because I found out that on my roaster (huky 500) when I use lower airflow - there is a chaff build up on the exhaust pipe and also chaff is falling from the front of the drum plate, so I decided to give it a try - Roasting with a higher airflow.

The thing is - I have noticed a sour taste in my coffee and I am also wondering if my beans will age much quicker that way like they usually do on an air roaster.

I would love to hear your thoughts regarding the above.

Thanks in advance.
Consider this excerpt from the following paper- I think he is onto something: http://e-collection.library.ethz.ch/view/eth:23461

"The amount of hot air in relation to the coffee batch size turned out
to be critical for roaster design and operation. Low air-to-bean ratios resulted in
coffee of superior cup-quality, whereas excessive air streams led to products of
bland, dull and flat sensory properties. A lower ratio is assumed to prevent physical
aroma stripping and excessive contact with oxygen and may create a favorable
"microclimate" enclosing the beans. These findings also stress the important role of
oxidation processes during roasting and storage."

GregR
Posts: 226
Joined: 14 years ago

#7: Post by GregR »

Regarding the chaff spilling down towards the stove area-- this decreased for me as the roaster became seasoned. In the early days I kept a shop vac handy and gave it a quick vacuum right before or around first crack. And as mentioned- a strong blast of the fan helps-- I do that right at the end of first crack and have never had any sort of chaff clog issue.

dustin360
Posts: 825
Joined: 13 years ago

#8: Post by dustin360 »

Mile High Roaster wrote:Consider this excerpt from the following paper- I think he is onto something: http://e-collection.library.ethz.ch/view/eth:23461

"The amount of hot air in relation to the coffee batch size turned out
to be critical for roaster design and operation. Low air-to-bean ratios resulted in
coffee of superior cup-quality, whereas excessive air streams led to products of
bland, dull and flat sensory properties. A lower ratio is assumed to prevent physical
aroma stripping and excessive contact with oxygen and may create a favorable
"microclimate" enclosing the beans. These findings also stress the important role of
oxidation processes during roasting and storage."


Schenker used an air roaster for his experiments, so this quote would be in line with what i would be thinking if I was using an air roaster. Too much air would probably create to even of a roast on a fluid bed roaster, which would lead to boring lackluster results on some coffees.

GregR
Posts: 226
Joined: 14 years ago

#9: Post by GregR »

Sour notes often come from drying the beans too quickly. They end up roasted on the outside and under-roasted on the inside. It's easy to do with Indos especially.

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boar_d_laze
Posts: 2058
Joined: 17 years ago

#10: Post by boar_d_laze »

GregR wrote:Sour notes often come from drying the beans too quickly. They end up roasted on the outside and under-roasted on the inside.
A result of too much heat cooking the outside of the bean more quickly than the inside. More a matter of going too fast through any or all of the intervals than too much air during drying.

Starbucks coffees suffer from this; tasting simultaneously burnt (scorched sugar) and "green" (sour). Sear and blast medium-rare works for steak but not coffee beans.

Rich
Drop a nickel in the pot Joe. Takin' it slow. Waiter, waiter, percolator

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