# Obligatory 'air v drum' thread



## MikeHag (Mar 13, 2011)

I'll get to the air v drum thing in a rounabout way, as my question also has to do with roast style/profile/design, and is based upon what I've learned through reading, not experience.

The degree of a roast (colour, eg as per Agtron) directly corelates with final bean temperature. Hence a roast is terminated either based on colour or (if you have the measuring capability) temperature (or smell, but I'll leave that for now). Air roasted beans will reach termination point sooner than drum. It will have a bright, more acidic character whereas drum roasted have a more complex yet muted character.

This suggests to me that the choice of air v drum comes down to the chacteristics you want from your roast. Here are some thoughts:

- it seems to me that drum roasting would be better suited to espresso and air roasting better suited to brewed coffee

- given the current trend in the uk for a lighter roast with more acidity, it seems to me that air roasting has a lot to offer

I know I'm skimming the surface here and opinions are welcome







I have no preference towards either roasting method but I do inherently question things that are the most popular (i.e. drums) simply because we humans have a tendancy to herd. (VHS or Betamax anyone?







)


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## CoffeeMagic (Aug 7, 2011)

Ahhhh... You've just opened another can of worms







but very good questions nonetheless.

Just to put one thing in context, i wouldn't get too hung up on Final Bean Temp since the value depends on where you are measuring it. You will probably find that it varies between roaster manufacturers. You are correct in what you say but be aware of how it is measured in each case.

Don't forget that some beans, specifically high-grown will tend to be acidy due to their slower growth. It can also be said that light roasts will tend to have more acidity, hence the tendency to roast darker for espresso. Again you are correct in what you say, but other factors should also be considered before coming to any conclusion.

Fortunately, I get the best of both having a drum roaster that also uses air blasts during the roast. Air roasting will generally produce a more even roast and can roast faster (not always a good thing). Although there is a trend for roasters to roast lighter, I'm not entirely sure that is customer-driven. There is a balance and a preference here regarding the chemistry of the roast - caramelisation and the Maillard reaction. Let's save that for another day







.

Practicality may play a strong part in using either to deliver both espresso and brewed coffee by adjusting the roast profile. My own opinion would be to not categorise any one method. Drum roasting is very traditional, whereas I foresee air roasting as becoming more mainstream in the long term or at least in the form of a hybrid.


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## MikeHag (Mar 13, 2011)

Thanks Ron. You've elegantly dodged the question







But yeah, hybrid models do seem on paper to be a good development in the industry. I can't wait to get hold of some beans from your Solar.


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## CoffeeMagic (Aug 7, 2011)

I have to admit that I pondered exactly the same thing in terms of air v drum. It's a dilemma that isn't easy to solve. There are the traditionalists in one corner and adopters in the other. Both create similar results but with subtle differences. Air roasting has been around a long time.

As regards your conclusions, you are probably quite right technically but not practically, if you see what I mean.

I'm getting the online shop done at the moment and waiting for more beans to become available. Hopefully won't be too much longer.


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## MikeHag (Mar 13, 2011)

I think I might understand what you mean about practicality, but I'm not 100% sure! Maybe a drum roaster is more practical for a roaster who wishes to produce beans for both espresso and brewed coffee, since seemingly using an air roaster would create more limitations in the choice of beans that could be used for an espresso roast... but I'm not sure.

This is so frustrating for me! I need to get some practical experience under my belt. I can almost grasp the technicalities, but like you say, actually doing it would reveal practical learnings that currently elude me.


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## CoffeeMagic (Aug 7, 2011)

Fundamentally, they are both practical at producing good espresso and brewed coffee roasts as the differences are subtle. There are many commercial roasters using Sivitz. They are probably the only company to solve the issue of roasting large quantities of beans using air.

At the home roaster level there are many air roasters - popcorn maker, Gene, etc. There is also a drum roaster - Hottop. The more popular is the air roaster. You might need to put one on your Xmas Wish List









Perhaps you should think of the roaster (whatever method) as a means to achieving an end result - a tool if you like. They all roast coffee from light to dark. With experience you get to know the best way of achieving the result you want with the least amount of compromise.


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