Fluid bed Vs Drum

[Javaphile]

Re: Fluid bed Vs Drum

Yeah that is an interesting link, too bad they dont post prices. :-/

Note the gas consumption on the larger ones, 5-6 times what drum roasters of the same size use. Even with being able to roast twice as much every hour as a drum thats still 2.5-3 times higher gas consumption. Their afterburners also consume more gas as the air is being moved through at a much faster rate.

Java "Hhhmmm...Technology!" phile

[Fresh_Coffee]

Re: Fluid bed Vs Drum

This has been a very interesting discussion particularly as it shows quite a deep interest and much articulation from home roasters, and as Java has said the topic is quite subjective. However, just a couple of points:

A) Java, re your description of what commercial roasters in the US do....this is not intended to be misinterpreted, it is just a simple fact that many are generally into burning good coffee by basically over-roasting. In terms of simplifying this style for the readership, this is basically the southern italian style of espresso roast...turn it black and let it "bleed" (oil). Over here we tend to follow the northern Italian espresso kind of roast which is not to roast much darker than a cinnamon coloured roast. This is mentioned simply so you will know that commercial roasting drums over here, are not as well "seasoned" with oily charcoal as you might think!

B) re: "....As my tastebuds became more educated to the different coffees and their flavors I found that in quite a few of the coffees I was buying from my local speciality roaster I could identify the bean that had been roasted before the batch I was drinking had been....." Hmmm. Really?

C) A recognized world authority on a lotathings coffee, our own Australian coffee expert Ian Bersten, designed and built several "shop" sized bench roasters of the fluid bed type, and he also designed and built (from memory so could be not quite correct but shouldnt be far wrong  ;D)   a 30 & possibly a 60 kilo fuid bed roaster atleast one of which (from memory) went into commercial roasting in Sydney. This was done at the same time as German manufacturer Neotech was doing much the same thing only going even bigger. Sivetz might have been working on the same things at the same time, or maybe later, cant remember.

It would be interesting for Ian to give us the benefit of some practical knowledge on the subject for purely academic reasons. He is very "scientific" and if he is able to give a comparison (between fluid bed and drum roasting), you should be able to bet your bottom dollar that it has been well researched and is..."no bull". Andy?

Cheers,
FC.

[papalui]

Re: Fluid bed Vs Drum

Interesting link Poundy. The 1.25 pound roaster looks interesting. I wonder what it costs?

[poundy]

Re: Fluid bed Vs Drum

http://www.sivetzcoffee.com/

Commercial size fluid bed roasting.

[Javaphile]

Re: Fluid bed Vs Drum

Given that all the most popular roasters are drum roasters rather than fluid bed I assume that there are a number of reasons for the preference.

Drum roasters are the most popular? Amoung what demographic? Amoung home roasters fluid bed roasters far outsell drum roasters. In the commercial roasting community drum roasters are used almost exclusively over fluid bed roasters simply because of their efficiency. Fluid air bed roasters (at least as they are currently designed) are economical only on a small scale.

The typically shorter roast times for fluid beds have been described as somewhat reducing the complexity of the coffee even though it is also described as brighter.

I cant speak for other roasters as Ive no personal experience with them but with my Z&D roaster I had no problem achieving the ideal roast time of 15-17 minutes simply by adjusting the amount of beans roasted.

Comparing the results of fluid bed to drum roasting where the beans are not taken to the same roast level is like comparing red and green applies.

Agreed, when dealing with the flavors native to that bean, but not when dealing with flavors that have been introduced from an outside source.

Drum roasters offer control of every aspect of the roast whereas the air flow in a fluid bed is usually not controllable without custom mods such as Mals. If fluid bed roasters offered programmable air flow during a roast they would be more in line with the flexibility of drum roasting.

I think the reason fluid bed roasters dont offer such a control is a matter of economics and idiot proofing. The fluid bed roasters are aimed at the entry level roaster and are priced and designed accordingly. Adding a variable fan control adds costs to its production and makes the roasting process no longer the set and forget experience that is in such high demand by the average consumer.

Since beans outgass during roasting the beans are not going to take up much flavour from a seasoned drum so I dont agree with Javaphile on that point.

As a drum roaster rumbles around with the beans rolling around inside it they are leaving behind their oils on the drum as well as plenty of smoke residue. Both of these of course having tastes and smells distinctive to the bean being roasted. When that roast finishes and the next batch of beans is put in there is plenty of these residues left behind. The new batch of beans are in physical contact with these residues as they tumble around in the drum. The residues flavors dont have to be absorbed via a gas exchange as they are being transmitted to the beans via direct contact. Look at what youre roasting your beans in. When you finish a roast theres smoke stains and, if you take the roast far enough, oils on the surface of your drum/bowl/collander/whatever. Unless youre using a drum odds are you wash your roasting container when youre done. Drum roasters dont get washed, those oils and smoke residues remain, ready to taint the following roast. And they can indeed flavor the following roast.

As my tastebuds became more educated to the different coffees and their flavors I found that in quite a few of the coffees I was buying from my local speciality roaster I could identify the bean that had been roasted before the batch I was drinking had been.

With us home roasters this is not as big an issue because we generally dont roast as dark as commercial roasters and so dont produce anywhere near as many oils nor smoke. While well pull a roast when it has at most a few specks of oil showing the majority of roasts I see coming out of the commercial shops are completely covered in oil.

As Im sure others here who sell such items will attest drum roasters need to be seasoned with a few roasts when first purchased and in fact every producer of drum roasters Im aware of tells you so in the owners manual.

The simple answer is that if you want to roast more than about 100-150gm at a time you will end up being a drum roaster.

This seems to be because of economics, not because the drum roasting process is neccessarily better than the fluid bed method.

Whew! That was several mouthfuls!

Now, with all that said I think the only people who would be really concerned with it all are the Single Origin roasters/drinkers. If youre doing blends the seasoning is a good thing. It adds depth and a broader range of flavors to the roast, exactly what you want in a blend. However, if youre doing SOs and want to taste purely that bean then those left-over flavors from the previous roast become an unwanted contaminant. :P

And so once again, we have a very subjective issue. It all depends on what youre looking for in your roast. There is no right or wrong answer, theres only the answer that works best for your tastes and pocketbook. As well as other highly subjective things like the willingness of ones other half to put up with ones obsession and tearing into appliances for that perfect part for your new roaster mod. ;D ;D ;D

Java "Off to put his fingers on ice to cool them off" phile

[garglebutt]

Re: Fluid bed Vs Drum

Given that all the most popular roasters are drum roasters rather than fluid bed I assume that there are a number of reasons for the preference. The typically shorter roast times for fluid beds have been described as somewhat reducing the complexity of the coffee even though it is also described as brighter. Comparing the results of fluid bed to drum roasting where the beans are not taken to the same roast level is like comparing red and green applies.

Drum roasters offer control of every aspect of the roast whereas the air flow in a fluid bed is usually not controllable without custom mods such as Mals. If fluid bed roasters offered programmable air flow during a roast they would be more in line with the flexibility of drum roasting.

I think the main gist of this thread was in relation to home roasting and for this you have a choice between: modified popcorn poppers and dedicated coffee "popper" designs like the iRoast, and some variation of a drum roaster starting from a heat gun in a dog bowl up to a HOTTOP or BBQ drum.

Since beans outgass during roasting the beans are not going to take up much flavour from a seasoned drum so I dont agree with Javaphile on that point. The simple answer is that if you want to roast more than about 100-150gm at a time you will end up being a drum roaster.

[Javaphile]

Re: Fluid bed Vs Drum

Then FC, can we assume that if a fluid bed roaster was to roast at the same rate (speed) as a drum the results could be as good?

Who says roasting with a drum produces better results than with a fluid air bed?

I have done many comparrisons of roasts done in my fluid air bed against the identical bean (both batches came from the same bag of beans) done by the speciality roaster in their drum roaster. In every case the flavor of that particular bean was crisper and cleaner in the fluid bed roasts with the drum roaster batches having a very muddied blend of flavors with the flavors peculiar to that bean being very noticably muted when compared to the batch from the fluid bed.

Much of this Im sure is attributable to the darker roasts coming out of the drum as they were standard production runs (see elsewhere in the forums for a discussion on this) and hence taken to a much darker roast than I would ever roast myself. However, with that said, the beans from the drum had flavors that did not come from that bean, but rather had crept in from the flavor of previous roasts. In some cases the taste of a previous roast wasnt even a background taste but was right there in the forefront of the flavors and was *very noticable.

The analogy that Ive come up with is that roasting in a drum is like cooking in a cast iron skillet while roasting in a fluid air bed is like cooking with a glass/pyrex skillet. When cooking with a cast iron skillet your food readily takes on flavors from everything ever cooked previously in that pan due to the seasoning of the pan with all those flavors never being removed from the pan with its washing. Cooking with a glass skillet on the other hand leaves the food tasting purely of itself as it has no seasoning due to its being thoroughly cleaned after each use.

It seems to me that as purists and true coffee snobs we would want to be tasting the flavor of *just the bean were drinking, not its flavor mixed with the flavor of 20 other beans as well. From this viewpoint it seems the cleaner, brighter roast produced by a fluid bed would be considered an advantage rather than a detractor of the method.

Java "Always experimenting" phile

[Javaphile]

Re: Fluid bed Vs Drum

I think you will find the "cleaner brighter" thaing relates to a ***quicker*** roasting time...

However there are other things in the total scenario to look forward to, so I am not necessarily in favour of the quicker roast.

Just "throwing something in from left field kind of thing..."

Regardz,
FC.

Hhhhmmm....It doesnt seem like that is the case as my roasts consistantly finish up in the 15-17 minute ideal roast time using my Z&D roaster.

Java "Still experimenting" phile

[Dimal]

Re: Fluid bed Vs Drum

I think you will find the "cleaner brighter" thaing relates to a ***quicker*** roasting time...

However there are other things in the total scenario to look forward to, so I am not necessarily in favour of the quicker roast.

Just "throwing something in from left field kind of thing..."

Regardz,
FC.

Hi FC,

Ive been using a popper for the last year or so and more recently, have modded it such that I can vary the fan speed. This allows me to tailor roasting profiles a little better than without this control.

For example, I can up the roast quantity to about 150 grams with a chimney fitted and by increasing the fan speed to maintain an active fluid bed, the roast duration can be extended to slow down the time to first and second cracks. With the above bean load, I can achieve a profile that brings on First Crack at about the 6-7 minute mark and Second Crack at around the 12-13 minute mark.

In doing this, I have never detected a change in the characteristic bright, clean nature of the roast but have definitely been able to achieve a SO roast with more body and mouth-feel, which I suspect is due to being able to extend the roast times.

For our needs, I dont really need to step up to a method that roasts significantly more beans than this but have been giving serious consideration to a modded Turbo Oven on a base with bean stirrer (a la Stir Crazy). Thought that this would allow me to maintain the flavour profiles Ive been getting with the popper but with a slightly more hands-off approach (have got very poor dexterity as a result of a couple of strokes). Will probably complete this during Winter.

Cheers,
Mal.

[Andy]

Re: Fluid bed Vs Drum

Then FC, can we assume that if a fluid bed roaster was to roast at the same rate (speed) as a drum the results could be as good?

In theory I would expect that a fluid bed roaster could have even better heat control because when you remove the heat from the air-flow it would cool near instantly (unlike the large metal mass in a drum) and could therefore use computer controlled roast curves fairly well to get similar results each time.

I know we have members keen on building larger scale fluidbed roasters (3kg ish) so it will be interesting to see how the prototypes turn-out.

[Fresh_Coffee]

Re: Fluid bed Vs Drum

I think you will find the "cleaner brighter" thaing relates to a ***quicker*** roasting time...

However there are other things in the total scenario to look forward to, so I am not necessarily in favour of the quicker roast.

Just "throwing something in from left field kind of thing..."

Regardz,
FC.

[Javaphile]

Re: Fluid bed Vs Drum

Ive been mulling over a thought on fluid vs drum here the last few days and thought Id throw it out to see what you might think about it.

Pretty consistantly you hear that fluid bed roasters produce a cleaner, brighter tasting coffee than do drum units.

One of the things I do when Im roasting a bean for which Ive already established a best roast point for is to vary the times on the roasts (my roaster does a 4oz/113g batch with 6 needed to produce a 3-4 day supply) by just a bit and then combine all the roasts.

This seems to produce a cup that is not as bright and with a more muddied blend of flavors, more like a drum roaster does but with-out as much of the smoke flavor.

Could it be that the cleaner, brighter taste the fluid beds produce is not only because of the recognized reason of being exposed to less smoke, but also because they are more evenly roasting the beans?

Java "The things one thinks of in the middle of the night..." phile

[Javaphile]

Re: Fluid bed Vs Drum

Well yeah...err...umm...ahhh...I give up, what was the question again?????!! ;D

All detailed out
Chiz,
FC.

I think it was do we float higher on coffee roasted in a Drum or a Fluid Bed roaster. ;D

Java "Floating away on the thin edge of caffine" phile

[Fresh_Coffee]

Re: Fluid bed Vs Drum

Well yeah...err...umm...ahhh...I give up, what was the question again?????!! ;D

All detailed out
Chiz,
FC.

[Javaphile]

Re: Fluid bed Vs Drum

Then again it could be the lighter beans on top will have more of their surface area exposed to the hot air as they wont be in as frequent contact with other beans making up for the slightly cooler air temp and causing them to roast just as fast as the heavier beans on the bottom. ;D

Java "Dont ya love science?" phile