Air roasted or drum roasted?

[MAXTOR]

AIR or DRUM

You wrote.“In my experience, it takes a mimimum of 12 minutes at a drop temeperature over 400 degrees farenheit. This has to be adjusted for type of bean and size of roast, as well as the style of roast.â€

 

[ralphshade]

So when were you a chef?

So prior to roasting coffee at the age of fifteen you were a chef? You must be quite the prodigy. :wink:

You don't seem to be picking up on my point. There a changes in the process that occur because of factors that cannot be accounted for. "There are more things in heaven and earth, Horatio..." I say you are a scientist because you aren attempting to reduce everything to a formula. There is some science behind the preparation of any food. There is also a great deal of inspiration and intuition. I do not not beleive that any machine can reproduce those things.

Hot air roasters have a much higher heat transfer rate than conventional drum roasters. The high air to bean ratio ensures a more rapid heat transfer than conventional drum roasters. This is one of the reasons why Air Roasters achieve the same result in half the time.

My entire argument against air roasting is that the do not produce the same result. You have even said so yourself. You have stated,

I also would like to add that it is taste at the end of the day and who likes smoked coffee likes it, probably because he never had a clean product.

You have been convinced, for whatever reason, that air roasted coffee tastes better. I disagree. This being said, I have no doubt that there will continue to be people like yourself who think that a computer can do their job better than they can. There will continue to be people who cannot appreciate the complexities in flavor and aroma that, in my opinion, are only developed fully in a drum roaster. There will also continue to be people like myself that love what is produced in a drum roaster over what is produced in an air roaster.

 

[nzroaster]

Although my personal opinion would back Ralphshade, there is no end to this argument. At the end of the day it comes down to the cup of coffee that you drink. The best coffee you can make is the one that the consumer prefers

"“I believe that there are factors that change with every roast, even if it is the same coffee and the same size roast. No machine can be programmed to adjust for them.â€

 

[MAXTOR]

NZROASTER

Thanks for your comments, this is not for arguments sake, its for understanding.

“What causes these changes is the climatic conditions, soil tempreture, and a number of many thousand other physical influences on the raw product. If you are claiming that every single green bean is physically & chemically identical, then that is a huge claim and if not then there is your answer.â€

 

[nzroaster]

"What I meant was lets say you bought a bag of Costa Rican Terrazzu and you roast that bag, are you saying that you are changing your roast parameters for the same batch of greens on every roast?
To adapt to what?"

yes, to achieve a consistant result. This probably sounds extreme and it is to illustrate the point that ralphshade was making about human input.

 

[MAXTOR]

NZROASTER

Here is my opinion about that:
Of course there are inconstancies within a bag. Smaller beans bigger beans, but I can assure you, you cant react to that.

If there is inconsistency beyond the obvious, its your process or your mood.
As I have said before, baby sitting a Drum.
(inconsistently)

I put this to you:
it is not an art to roast good coffee, but it is an art to control a drum roaster.

Its Like TD said in the SCAA forum

"I agree absolutely with holding your airflow constant when roasting. It is necessary to hold at least one of the variables constant or you are never sure which variable is actively affecting the roast. Additionally, if you restrict the airflow, you will also affect combustion (more in some roasters than others) thereby adjusting the heat input whether you intended to or not. If you then attempt to adjust both, you can begin to chase your tail, as you have no accurate way of measuring which variable is slowing or speeding the roast. Airflow is the most obvious variable to hold constant as it is the hardest to accuratley control, and if you are using good quality coffee you should want as clean a roast as possible so why restrict your airflow?"

So consider this, Greens can not be blamed for lack of process control.

 

[MAXTOR]

NZROASTER

I just read your post on SCAA Roasters Guild topic Drum Vs Fluid Bed.

For the amount you are roasting per day, there is no affordable Air Roaster available as of today that would be able to give you the control over process.
Typical Air roasters have a limitation, which is airflow.
You have no idea how much Airflow you would need to lift a one-bag batch.
The heater to heat such airflow would be in the hundreds of KW’s.
Although development moves towards Air Roasting, for bigger machines there needs to be mechanical movement to move the beans.
However, true commercial Air Roasters that are small batch machines like 1-2 KG per batch with a max of 80 respectively 160kg per day.
You would need 10 of them to turn out what you need.

I had a interesting conversation with Probat engineers 2 years ago.
They have a roaster that uses drum for movement and air for roasting called Therma II. This roaster has roasting times between 3.5 to 10 minutes and a batch size of 120 kg Cost I think around a million EURO.
Of course they have done their homework, Probat is long enough in the business to know what they are doing. Anyway the bottom line is this Probat told me that you can achieve a full developed roast in 4 minutes. And that is not only measured by cupping but by chemical analyses and content profiles.
The key is simply Heat Transfer Rate. Meaning how fast can your system transfer heat to the core of the bean.
And if you read through the posts top down it is explained why Air Roasters have those higher heat transfer rates.

What makes a good air roaster?
Profile roasting programmability of up to 10 different time and temperature steps.
Total control over temperature variance + - 1degree C
Total Control over airflow.
Total Control over time.
Cooling cycle not longer than 2 to 3 minutes from 240 to 30 degree C
Computerized, programmable.
Quiet

Roasting with an Air Roaster does not mean I cannot roast for 15 or 18 minutes.
Some times when I do Aroma profiling we take different approaches.

For example LTLT ( Low Temperature Long Time)

Brazil Santos Dark Roast
Batch 1kg
Temperature: 216 C
Time: 900 seconds

Impact of Roasting Temperature Profiles on Chemical Reaction
Conditions in Coffee Beans
S. SCHENKER1, C. HEINEMANN, M. HUBER, R. POMPIZZI, R. PERREN,
F. ESCHER*

As you can see from the above LTLT is used as 100% so in order to achieve roasting profiles for optimum Aroma development you need to have total control over process.
In an Air roaster you decrease or increase or hold environment temperature fast and efficient and there are few parameters to control.
In a Drum you have similar parameters with the addition of the drum it self and any adjustments with the exception of heating up constantly is too slow.
This is despite the fact that if you don’t keep max airflow going in the drum you going to end up with smoked and tarred coffee. Like 98% of what is available Globally. Everyone who cleans his drum has to got to ask him self how much of that dirt and tar actually ends up in the product.
But as I said for your size, I don’t think that a Air Roaster of a size you would need it is available right now with a full on process controller.

 

[nzroaster]

point noted.


PS, Really like your signiture

 

[MAXTOR]

NZROASTER

Thanks, just added another line.


Sorry ralphshade

I overlooked your post. I get your point and I agree.
Air Roasters don’t have all the smoke, tar and carbons added to the product roasted in drums in some drums more and in some less.

Right, complexities in flavor and aroma, you could call it that too.

“I have played with the little "home" hot air roasters...wasn't too impressed...you put the coffee in turn a dial and it turns the coffee brown...no airflow adjustment...no heat adjustment it is all or nothing..true I have never used a "commercial" air roasterâ€

 

[Alun_evans]

This strikes me as being a pretty similar type of discussion as you normally see between drum and fluid bed roasters...ie: the roaster using either type is normally not going to bend on their support of their particular method of roasting! In a couple of weeks time there is a coffee exhibition on in Singapore, I am going to be there. Incidentally Maxtor will be exhibiting there also....so how about I (a confirmed drum roaster myself) have a look at the air roaster in action. Hopefully we can settle this debate once and for all :wink:

 

[MAXTOR]

Alun, you blew my cover.

You figured me out yesterday, don’t know for sure how you did that,
but you did well
I get onto these boards once a year, as I am pretty busy.
Just took a few days off to have some fun.
I am looking for valuable arguments, the pros and the cons.
If the guys know that I am actually building Roasters they would not bother and it would be like yea yea this guy is on a sales pitch.

Just have to look at the first line of responds I got from topher after my first posting.

“do you own a popcorn...sorry air coffee roasting company?â€

 

[Alun_evans]

Actually the fact you build them probably gives you more credibility than if you are just a roaster using one. As you said about the guys at Probat...they build them..they have surely done their homework. How I figured it out... :wink: ....will tell all when we meet in Singapore.

 

[phaelon56]

As with most arguments, there are two sides and this one certainly has spirit on each. Some of the best coffees and espressos I've ever tasted came from drum roasted beans. The coffee that was quite possibly the very best I've had was at an Ethiopian Coffee Ceremony - roasted in a beat up bent old skillet on a gas stove and then crushed into rather inconsitently sized particles in a mortar and pestle before being steeped and served. My point being that with the right technique being employed by a person who has the passion and desire to produce excellent results.... the type of equipment is not the sole factor.

My opinion is that air roasting (fluid bed) has tremendous potential that has not been unlocked or fully developed. I've played with and used consumer style hot air roasters (e.g. a West Bend Poppery) and also consumer drum style roasters (Alpenroast). The hot air poppers can be modified with a Variac (voltage regulator), allowing the roaster to extend roasting time to 12 to 15 minutes or even longer if desired, including a plateau between first and second crack to more fully develop the flavor profile. Small consumer drum roasters, by virtue of design, typically yield a 15 - 19 minute roast time. Espresso enthusiasts often express a preference for the mellow flavor profile and full body (with less acidity) that small drum roasters produce. It's my impression that the voltage regulate small hot air roaster offer the best of both worlds.

IMHO this is where the problem arises with the most popular type of commercial hot air roasters, the Sivetz. I'm using one right now - the 1/4 bag model. Just to clear up an inaccuracy from an earlier post - hot air roasters such as the Sivetz come in models as large as 1 bag units (those roast a full bag of green beans at one time - about 150 pounds.

Our Sivetz offers an incredibly high degree of repeatability and consistency even when used by an inexperienced operator like me (I have lots of coffee and espresso experience but have only been running a commercial roaster for five weeks). Note that I said "operator" and not "roaster". I consider myself to be a machien operator who hopes to learn enough to become a true roaster.

Our roasted coffees do have a brighter finish than most drum roasted coffees but our customer base loves what we serve. I believe it can be improved. Our typical roast times are in the 9 - 10 minute range - not long enough. The gas burner on a Sivetz has little adjustability for heat output - it's more or less constant. The airflow is also more or less constant and I've been unable to find a method for increasing the outflow, only the inflow.I'm looking for ways to reduce the amount of incoming hot air and lengthen the roasts to 12 to 14 minutes.

If the experiences that home roasters have had with developing profiles hold true for commercial fluid bed roasters, it's conceivable that I can produce results every bit as good as drum roasters but it will still be different and again.... it always boils down to personal tastes.

Different strokes for different folks. My sincere desire is to develop some ways to truly control roast time and profile with the Sivetz and then get some experience under my belt with a commercial drum roaster. perhaps then I can make some valid A/B comparisons. Until then I'm thankful that I have a chance to work in the coffee business in some small way - it's very satisfying even though I still have my "day job".

 

[MAXTOR]

Owen
I agree with what you say in regards to passion and I think anybody would.

With air roasting there is a flavor not present and that are carbons and smoke, taste and smell. But I believe that most people would agree that is not something desirable.
Experienced Drum Roasters stress to work with as much airflow as you can to avoid carbonization.
Considering that coffee is one of the healthiest beverages this would not add to the benefits.
Everything else you can develop with a hot air roast.


I am not familiar with Sivetz as I mentioned before, but what you describe here to me sounds like all you do is put a bag of coffee into a hot air stream with no control of airflow and temperature and you just wait until the coffee reaches the desired roast color and than you drop it.

Questions how do you cool?

We have been at this stage maybe 5 years ago.

I can not stress this point enough, hot air roasting has a much higher heat transfer rate. If you roast 15 minutes in an Air Roaster like the one you describe it is the equivalent of a 30 – 40 minutes roast in a drum.
No one will do that.

Yesterday I roasted one-pound coffee at exact 218 degree C for 600 seconds.
I could roast this coffee for one hour and still would not hit second crack.
As you say air roasting has potential, it does.
But you need to have 100% control over: Airflow, Temperature, Time. And you need to be able to change those parameters at least 5 times during one roast cycle.

Here is a roasting profile that I use for one of the beans.
T= Temperature A= Airflow T= Time S= Seconds

Preheat 190 Charge 2 pounds Cooling 120 S

T A T
190 100% 100 S
200 90% 60 S
210 80% 60 S
220 70% 80 S
230 70% 80 S
240 65% 60 S
245 65% 80 S

Ethiopia sidamo dark roast.

If you cannot do that with your air roaster, you are basically roasting , applying one temperature and you let the greens gear up to that.
And that leaves you little possibilities for profile roasting.
And little profiles mean little Aroma management.

 

[phaelon56]

There are ways to modify the temperature and the roasting time with a Sivetz. But.... someone needs to come up with a separate PID for temps and a microprocessor control with programmable profiles that can be stored in memory. The profiles would control airflow and times. It's not rocket science but I'm not a real hardware hacker and lack the skills. Not to mention that it's not my roaster I'd be messing around with

I discovered a way tonight to ramp up the temperature differently in intervbals rather than just blastign with one styraight inlet temp, a corresponding straight up slope in rising bean temp and no real profile. Sivetz supposedly has a profile built into their system but I've watched the inlet temp and beans temps and gauged their progress over time. Sure doesn't look like a real roast profile to me.

I did find a way to reduce the burner flame size, thus lowering inlet temp and allowing me to extend the roast to 12 to 14 minutes. My preheat temp is low... about in the 150 degree temp if I load a new batch of beans quickly enough after the previous roast. I have reasons to think that tonight's batch of beans will be superior to what I was producing with 9 - 10 minute roast times but won't know until the beans have degassed for a day or two and I've had a chance to try them out.

The big issue right now for me is easy repeatability - these are subtle manual physical tweaks but I still see potential. The guy who used to do our roasting loved the concept of the Sivetz but hated some of the usability issues and the lack of ability to create profiles. He's currently building a 7.5 lb fluid bed roaster of his own design with plans to resell them and then add larger capacity models.

I think it's helpful to leave small consumer style popcorn poppers and hot air roasters out of the discussion altogether just as it's not fair - the large comemrcial fluid bed roasters are an entirely different beast.

Alpenroast 1/2 lb capacity electric drum roaster to a Probat. They operate in different universes - it's apples and oranges.