At my last job, we recycled tires by breaking them down into carbon, steel, and crude oil. We were able to do this by adding a chemical catalyst and super-heating the tires. This occurred inside a vacuum reactor - in an open environment, the materials would have turned into a massive fireball. But by eliminating the preconditions for a fire, a different chemical process would occur.

My idea: why not try this with coffee? The potential for a vacuum-roaster is very exciting. How would this affect the chemical reactions that occur throughout the roasting process? Would coffee taste better with no oxygen exposure during the roasting process?

It would be interesting to experiment with this on a small scale. One could take a sealed drum roaster, use nitrogen to flush out the oxygen, and then create a vacuum in the drum before roasting. Additionally, the drum should have a one-way valve for the nitrogen flush and in order to release any pressure that could potentially build up.

What do you think?

According to the roasting chapter in Illy, nitrogen flushed roasts tasted the same as regular ones. This is not surprising; since coffee roasting is a Maillard reaction which use amino acids, sugars and water as the source reagents.

The environment in the roast chamber will mostly effect heat transfer abilities. I spoke with a friend of mine who is an engineer who works with energy. My question was around the differences in heat transfer abilities between O2 and CO2. We did not talk about the effects of pressure. My guess would be that a high pressure environment (like a pressure cooker) might speed up getting heat energy into the bean but not sure it would have any benefits when it comes to roast quality. The effect I see with O2 has more to do with HO2 management relating with time. A vacuum or pressurized environment would also have to deal with expulsion of the moisture.

Am I wrong in thinking that oxygen must be present to carmelize sugars?

Adrock wrote:At my last job, we recycled tires by breaking them down into carbon, steel, and crude oil. We were able to do this by adding a chemical catalyst and super-heating the tires....
My idea: why not try this with coffee? The potential for a vacuum-roaster is very exciting. How would this affect the chemical reactions that occur throughout the roasting process? Would coffee taste better with no oxygen exposure during the roasting process?

Judging from some of the burnt rubber flavors I've gotten from restaurant coffee, some roasters may already be using recycled tires in their production!

But seriously: most of the chemical reactions going on in coffee roasting are happening inside the bean. And since during roasting there is a strong flow of water vapor (initially) and CO2 (later on) from inside the bean to the environment, even in a conventional roaster the reactions that matter are occurring in a low oxygen environment.

Damn - I thought I had a good idea. At least I won't waste the time and money on an experiment now.

Perhaps the coffee being bathed in its own smoke and water vapors might give it an earthier, smokier flavor?

JonR10 wrote:Am I wrong in thinking that oxygen must be present to caramelize sugars?

I think so - sugar, water, a little acid will do it.

Adrock wrote:My idea: why not try this with coffee? The potential for a vacuum-roaster is very exciting. How would this affect the chemical reactions that occur throughout the roasting process? Would coffee taste better with no oxygen exposure during the roasting process?

There's a thread over at the GCBC here about a nitrogen based "airless" roaster being developed for field deployment, but I believe that the driving factor was explained to be a way to avoid heat loss during roasting.

The thread has gone quiet for a few months, so I don't know what ever came of this project.

-Chris

I just don't understand what happens with the moisture in a closed system.