"Room" temperature is one of many possible temperatures for just-roasted beans...

Roasted up a small batch (130g) of Nicaragua Buena Vista Obata using an 8-minute (IKAWA) linearly-declining RoR roast profile to what looked like a City-ish roast level - at least that's what it looked like immediately post-roast. It's typical for my roasts to advance another half-level (e.g. City+ to Full City) after a week's rest.

I split the just-roasted (about 15min post-roast) beans across two vacuum-sealed bags, large enough so the beans could lie flat in a single layer in the bag. So the environment around the beans in each bag was the same. The vacuum turned them into a stiif, flat, sheet-o-beans:



One bag was left to hang out at room temperature, and the other bag went into my sous vide bath set to 60C/140F for 24 hours. I picked the temperature as a compromise between food safety, and paranoia over driving out all the tasty volatiles. I'd consider other temperatures if I can find a table of the vaporization temperatures of the key (good tasting) volatiles in roasted coffee. Stopped at 24 hours, because going longer would seem inconsistent with the whole point of accelerating the resting phase.

After 24 hours, both bags felt equally rigid, essentially just as stiff as when the original vacuum was pulled. Interesting... I've been programmed to think the little vents on bags of commercially roasted coffee are there to allow the beans to degas post-roast, so I was prepared for my sealed bags to inflate like balloons. LOL, I fooled myself. Now I'm more inclined to think the air vents are meant to keeps the bags from exploding when they're trucked over mountain passes or carried on an airliner.

The sous vided beans were ever-so-slightly darker. If I had a roast color analyzer perhaps it would be just enough to register a 1-point difference. Same was true for the ground beans. There was a difference in smell, with the room-temp beans having a stronger 'nose', but nothing offensive with either group.

Cupped the grind at about 13:1 brew ratio. The room-temperature-rested brew had slightly more foam on the surface after the hot water was added. The brew color for the cooked beans was notably darker, and curiously, less cloudy. I can't think of why the suspended solids would be different between the two.

After five minutes I started tasting: the sous vided beans were smoother, milder, no bitterness or sour notes. The room temperature rested beans were stronger, with some definite sourness. The cupping differences were the same after letting them cool down another ten minutes.

So, did I just bake my beans, or did I accelerate the resting process? The sous vided beans made a smoother/milder cup of coffee, which could be the interpreted as similar to a baked roast profile. However, these particular greens have shown a similar, mild taste profile after a week's resting time at room temperature. Next time I'll try to use punchier greens.

Just letting the roast rest at room temperature for a week or so is certainly the simplest approach, but sometimes I get in a pinch.
Grinding the beans and letting the grind rest for an hour is also a proven technique - but that's in the path between me and my coffee that morning. Dropping the roast into a ziplock bag and floating them in my sous vide could come in handy from time to time. I'll be trying this with different origin greens and posting updates. And I hope others also give this a go and post their results - it only takes a couple doses (e.g. 18g) of beans to experiment.

GDM528 wrote:
After 24 hours, both bags felt equally rigid, essentially just as stiff as when the original vacuum was pulled. Interesting... I've been programmed to think the little vents on bags of commercially roasted coffee are there to allow the beans to degas post-roast, so I was prepared for my sealed bags to inflate like balloons. LOL, I fooled myself. Now I'm more inclined to think the air vents are meant to keeps the bags from exploding when they're trucked over mountain passes or carried on an airliner.

I would have thought they would degas and bags expand. I know I've done this with fresh chesnuts and the bag seems rigid the first day. But let it go a week or so and the bag will balloon. So I'd say you have to leave it for more than 1 day to get a conclusion.

perhaps the vacuumization draws (some of) the CO2 out already, indeed a longer wait seems necessary...
I read the problem statement as lack of time to wait for a fresh roast to degas, why not try grinding a small batch post roast and vacuming that for a bit for use for the next morning without sous vide?

This reminds me when I caramelized white chocolate in a sous vide water immersion bath and pressure cooker a few years back. I think the sous vis method took about a week at 180F or something like that (a quick google search brings up influencer or AI generated results only, don't trust those) and pressure cooker was for a few hours. These aren't much different from doing it with onions and garlic as well.
I wonder what would happen if you tried this with greens, or already roasted? Results would likely be terrible, but would be fun to try if you have the time to do so I'm putting on my todo list now, but it'll be months before I can get to it, so maybe someone will beat me to it.

I tried doing a pre roast sous vide, result was the same as a normal roast unless you charge preheated greens (which then only shortens the roast, no taste differences)

My conclusion was that the formation of taste components happens at pretty high temperatures.

Nice work! My initial thought would be that resting at an increased temp drives some CO2 out of the beans (apparently not a lot), meaning that perhaps there is less CO2 to coat the grounds (which make them float in suspension and causes that foam) and less carbonic acid in the cupped brew. This might be perceived as more balance in your cupping or in it's extreme, flatter.

It is surprising that the SV pack didn't balloon at least a little, and it might be that each sample is fairly small at less than 65g.But I'm with you that offgassing of CO2 might be a bit overstated. I did recently get some beans from Hawaii which were sealed without a valve, and the darker roasted beans were tightly ballooned. I think you're spot on thinking that it's more a shipping thing where they're accounting for locations at different sea levels.

I'm really glad you did a control group and cupped them side-by-side. Another interesting control would be a sample rested in a container with a looser top. I've got it in my head that the first 24h offgasses campfire tastes that tend to make coffee taste harsh and your setup would isolate that. Just a thought!

Would love to see one with some beans put directly in the freezer, one sous vided, and one left to age normally at room temp. It would also be interesting to try to see how much the sous vide for a day would age them. This could be done by doing the sous vide and then put them in the freezer while letting the room temp age a week or so. Then taste them to see if they are closer. I'm not sure how much influence freeze/thaw would have on the results though.

Cool stuff! I'm curious about the ballooning bag myth as well. Maybe that is more common with dark roast coffees? I notice that Prodigal does not use a valve on their bags. I have noticed in the grocery that there are the vacuum sealed bricks of pre ground coffee like Bustelo that do not balloon. That is very dark roast. I wonder if they age the beans before packaging? Or like a previous poster suggested, maybe the vacuum process pulls all the CO2 out.

I suspect it's the grinding that handles the CO2 with preground.

It's not just removal of CO2 that improves the flavor of roasted coffee over a period of rest-it's also oxidation. I don't think the oxidative effect would be equal here. Accelerated aging studies function similarly, however: one sample (a reference or control) is kept, and the experimental sample is placed in an environment that is warmer. The rule of thumb for this is that rate of chemical reactions (including oxidative reactions) doubles for every 10ºc increase in temperature-so, in theory, if you had a coffee at 20º and one at 40º, the one at 40 will "age" 4x faster.

My question is, how do I explain to my wife why I'm using the sous vide to age my coffee beans?

I don't see any good outcomes.

I roasted enough this weekend to have a little surplus, I plan to freeze some so I have for contingency plans, and I need some beans to tide me over for a few days while I let a roast rest.

I do like this experiment and appreciate your sharing.

Randy