Marcelnl wrote:That I find hard to believe since direct oxidation which forms CO2 is unlikely.

I think you are right. I was repeating some roasters idea about this but it wasn't based on any science.

Pressino wrote:That would explain my experience that the amount of crema produced by dark roasted coffees decreased more rapidly over time than it does with lighter roasts. :!:

Moderator note: What appears to be the source article for above image: https://www.researchgate.net/publicatio ... ted_coffee

buckersss wrote: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.

Done!

City+/Full-City roasted some washed Colombian greens and vacuum bagged'em. Beans were laid out flat to minimize the air trapped between the beans and hopefully give me a more clear indication of outgassing. I've previously tested my Foodsaver and found it doesn't pull a very strong vacuum, about one-half atmospheric pressure - but that's still strong enough to draw the plastic film tight around the beans, enough for the bag to curl a bit. On the other hand, laying the beans flat makes the bag size capable of hosting a large volume of gas, so no 'ballon' likely. The sealing mechanism can't come any closer than about an inch to the contents, so I wouldn't have been able to form a tight seal around a more spherically shaped bean mass.



Bag had relaxed by day three, and the beans were loosely moving around by day 5. After a week the plastic film was still resting on the beans. It would take a lot more than this 55g sample to generate any 'lift'. Besides, how much pressure is that CO2 gonna produce at 25C, after having been developed during the roast at 220C?

"Bag hit", you ask? Immediately upon opening the bag, it had a strong olfactory impact, similar to a full (12oz) just-purchased bag of dark roasted coffee, with perhaps slightly higher plasticky and phenolic notes. Taking daily hits of a similar quantity out of a ziplock bag is a more pleasant experience, so, patience not a virtue in this case.

Terminated the test after day seven so I can drink that coffee, finally!

Sous Vide Temperature Test

Nicaragua Buena Vista Obata greens (Klatch), roasted to City+/Full-City using a linearly-declining RoR 8-minute profile on an IKAWA Home roaster. Yielded three 55g batches of roasted coffee, distributed into three sealed plastic bags.

Each bag was held at room temperature, 60C(140F), 80C(176F) respectively, for ten hours.

Cupped each sample, fine grind, approximately 14:1 brew ratio:
No significant difference in crust/foam between the samples.
All had a pleasant aroma, growing increasingly weaker for the higher resting temperature.
Room temperature sample was the harshest, from a combination of acidic and sour notes - however, it was still quite pleasant.
60C sample had no harsh notes, slightly weaker overall strength, but more sweetness. Remarkably pleasant drinking experience.
80C sample had notably weaker overall strength, and interestingly seemed to add back some sour notes. Kinda bland.
Comparisons were identical as the samples cooled to room temperature.

My overarching observation from cupping was: "why am I drinking espresso?" The long steeping time and high brew ratio seems like a bomb-proof way to enjoy coffee. Espresso drinkers must be in it for the challenge.

Tried pulling shots. 18g, extended preinfusion 'bloom', 34g out:
Crema identical between samples.
Tasting notes exactly mirrored the cupping notes - but greatly exaggerated. The room temperature sample was harsh and unpleasant, the 60C sample was 'ok' but no sweetness, and the 80C sample was more bland and more sour - but still better than the room temperature sample.

So, 80C is too hot, and 60C does seem to take the edge off freshly-roasted coffee enough for next-day drinkability. This will be a useful hack for the occasional circumstance when I can't roast a week in advance. I wouldn't do this on a regular basis, as the 80C results seem to imply that I'm messing with the flavor balance of the rested coffee, and I presume that accelerated resting is also accelerated staling, so I would only sous vide a few days worth of the roast and let the rest catch up at room temperature.

Why not compare with 'fresh roasted, immediately ground and kept in a sealed jar'coffee?
When travelling I take my Robot and pre ground coffee, usually lasts quite well until approx 7 days after grinding.

One thing I've observed with vacuum sealing is if I seal to complete vacuum using my food saving, my bags never puff/loosen up even after a week. When I open these bags there is usually a distinct lack if aromatics. If I repeatedly vac seal the bags the coffee seems to lose flavor at an accelerated rate. As a result I generally never pull a full vacuum unless I'm freezing coffee.

If I seal the bag just before I pull a full vacuum, after a few days the bag is bloated. Opening these puffed bags reveals much more aroma and the coffee subjectively tastes more flavorful. I've often wondered if the coffee flavor, as least as I enjoy needs some amount of oxidation or if there are other processes happening as it ages to bring the most desirable flavor out.

I certainly wouldn't be mad if a way was discovered to decrease the amount of rest time I needed to wait post roast before I enjoyed full bliss

Marcelnl wrote:Why not compare with 'fresh roasted, immediately ground and kept in a sealed jar'coffee?
When travelling I take my Robot and pre ground coffee, usually lasts quite well until approx 7 days after grinding.

I have tried pre-grinding, and I consider it comparable, one of several hacks to dealing with just-roasted coffee that people can adopt (or not) to their unique circumstances. Unique to me, I already happen to store my roasted coffee in ziplock bags (no vacuum, just push out the excess air before sealing) and I happen to have a sous vide sitting full time on my countertop. So it's very easy (aka lazy) to simply float the bag of coffee in the sous vide overnight.

SutterMill wrote:If I seal the bag just before I pull a full vacuum, after a few days the bag is bloated. Opening these puffed bags reveals much more aroma and the coffee subjectively tastes more flavorful. I've often wondered if the coffee flavor, as least as I enjoy needs some amount of oxidation or if there are other processes happening as it ages to bring the most desirable flavor out.

I've observed the same effect as I use regular ziplock bags for my daily-use coffee storage. I had attributed much of the bag's expansion to an imperfect seal and the beans in the bag pushing the walls of the bag apart. Now you have me wondering if there's yet some other thing going on that's producing enough gas to visibly 'inflate' the bag...

I can relate to the bag hit effect before brewing. I've never tried rigorously testing if it's real or psychosomatic, but I have found roasts that look good and smell good also taste good.

Give it a try. I typically stop/seal the vacuum just as the plastic starts to form around the beans. A majority of the air has been evacuated and some vacuum has occurred, but very little.
One thing to note. I very rarely go very far into second crack. Meaning most of my roasts are city to full city. Rarely city+ or beyond.