A new coffee storage paradigm

[tmaynard]

Thesis: Green coffee beans are shelf stable for a year or two. Roasted coffee beans are shelf stable for 10-12 days. During this time, the roasted beans are out-gassing CO2.

Lemma: When the outgassing ceases, the beans are stale. This outgassing is a by-product of the roasting process.

Lemma: A process that slows or halts the CO2 outgassing will preserve the "freshness" of roasted beans.

Conclusion: Storing beans under negative pressure (partial vacuum) is simply wrong because it will expedite the outgassing of CO2. The negative pressure is "sucking CO2 out of the beans." Storing beans at atmospheric pressure will restrict outgassing to normal rates. Storing roasted beans at positive CO2 pressure will decrease or halt the normal outgassing, thus placing the beans in "suspended animation" and limiting outgassing.

Note: I am *not* saying that you can keep beans "freshly roasted" indefinitely, nor that you can "recarbonate" roasted beans. I am merely positing that beans kept under CO2 pressure will remain at a post-roast freshness level longer.

Admittedly, beans kept under positive pressure with nearly any (non-toxic) gas should accomplish the same end, but CO2 is the natural outgas, and is easy to obtain and manipulate.

Okay: Bring on the flames! Is this just nuts? If so, where and why? Where is the hole in the logic? What is the defect in the design?

It just kinda seems obvious to me, but I'm biased a bit.

Tom.

[farmroast]

It's the o2 that causes the staling. CO2 does protect the beans and is better to have in the contained bean environment. Too much co2 in the bean as in just after roasting and for the first day or two will when mixed with water and saliva creates carbonic acid that adds a bitter/sourness to the cup. One of the reason the cup taste better after a various amount of rest. The thought with the vacuum just after roasting is that most of the o2 is removed the outgassing of co2 will create a neutral environment. This can buy you a few days but once opened the beans will have released much co2 and o2 will quickly enter the beans. I pretty hard to beat mother nature.

[mldavis2]

Thesis: Green coffee beans are shelf stable for a year or two. Roasted coffee beans are shelf stable for 10-12 days. During this time, the roasted beans are out-gassing CO2.

Lemma: When the outgassing ceases, the beans are stale. This outgassing is a by-product of the roasting process.

Tom.

I'm not sure it's correct to say that the beans are stale once outgassing of CO2 ceases. They are stale once critical aromatics are oxidized. There is a small amount of oxygen in each bean, so even roasted beans that are vacuum packed will stale over time, although not as quickly. The question might better be asked if negative or positive CO2 pressure is better in inhibiting oxidation. I suspect it wouldn't matter all that much unless you could find a way to extract the oxygen.

[kaboodle]

I agree...roasted coffee is not stale (at least not by my tastes) when out-gassing has ceased. I haven't done any scientific measurement of the out-gas properties by day, but judging by the amount of pressure remaining upon the sealed lids of my Mason jars sealed with a FoodSaver, most of the serious out-gassing is done in 3-4 days. Some of my blends don't come into full flavor for a day or two after that point and are at their peak flavors. The roast level plays some part as well. If the beans are roasted to the point where oils have emerged onto the surface, those oils can become rancid over time and produce a loss in flavor. My roasts don't get any more than about 10 days shelf life, so I rarely have felt that the coffee flavor suffered or when stale. The flavor certainly does fall off once the peak has been reached, but not so much that I would consider it stale.

Rick

[mldavis2]

We should all be experts on stale coffee, as I'm sure we've all consumed our share. My real problem is that, now that I roast my own, I've forgotten what stale coffee tastes like. (I seem to recall essence of cardboard and ash but those taste receptors haven't been exercised in a while.) I've become a real coffee "snob" (enthusiast is a better term) to the point where I will not drink coffee that comes from a percolator or a dime-store drip brewer unless the offer is connected to an event of such importance that refusal would result in dire personal or political consequences. Joy is having fresh roasted coffee on demand. I never roast more than I can consume in a week or less, and I roast about 2 days ahead, forcing myself to forgo any temptation to sample a new roast too early. Self-discipline, I keep telling myself......

Along the same lines, I do prefer to store my freshly roasted beans in a Tupperware container rather than a plastic zip lock bag. My beans come slightly warm from the iRoast (it does a good job of cooling quickly) and are poured onto a thick aluminum baking sheet (with sides) to cool at room temperature for about an hour, then they are placed in the container with the lid on. Thin plastic will allow aromatics to permeate the container (smell the bag and you'll see that it doesn't hold the aroma completely), while the much thicker Tupperware container virtually eliminates odor from escaping. The Tupperware is also easy to toss in the dishwasher to clean up any stale oils that might collect on the sides. The top is flexible enough that I've seen no signs of CO2 buildup, although it would just pop the lid up on one corner.

[Sweet Maria's]

Agree with the other replies. It's not about "sucking out CO2" but rather, oxidation. That said, I am as much a fan of vacuum-packed roasted coffee as I am of holding brewed coffee in airpots. Sure, it works, especially in the short term. But it certainly does not halt staling/aging, and maybe more significantly, it sends the wrong message about coffee ... I mean, for me home roasting is as much about a new approach to coffee, treating it as a fresh and fragile food item, as it is about any particular technique to accomplish the result ... and that is, having small amounts of fresh-roasted coffee and enjoying it before all those fleeting volatile aromatics split the scene, and before O2 has a chance to stale the lipids, etc. Of course, same goes with new appraches to brewing and espresso as well. Can you imagine pulling a beautiful shot, then putting it in a mini thermos to enjoy a few hours later?

[tmaynard]

Agree with the other replies. It's not about "sucking out CO2" but rather, oxidation.

Perhaps my intent was never made clear: I'm not talking about long-term storage, I'm talking about storage for the 10-12 days that roasted coffee may remain "fresh." I'm talking about doing what's necessary to preserve that peak of freshness throughout the normal staling period -- if that makes any sense.

I'd like to brew a cup of coffee at 12 days' rest that tastes like a "normally stored" brew at, say, 6 days' rest. I'm trying to "prop up" the staling curve, even if just a bit.

for me home roasting is as much about a new approach to coffee, treating it as a fresh and fragile food item

Exactly! And I'm searching for a way to take that to another level, attempting to maintain that peak of freshness in an optimal way, that's all. Hence my CO2 pressurized storage idea: keep oxidation at bay, keep the beans from outgassing (or outgassing as much), keep everything in a fairly neutral environment -- although CO2 can be acidic under some circumstances. Nitrogen storage is another option.

In all cases, it still seems to me that a neutral environment, at positive pressure, will (A) keep oxygen at bay, and (B) slow down the escape of volatiles from the beans. I didn't read any response that truly refuted those points.

Of course, the proof is in the pudding: roast a batch, keep half in air-tight, room temperature containers, and half under pressure. Brew each at various intervals (daily) and contrast/compare. While I doubt that my palate is sensitive enough to detect subtle differences, I might notice a major change.

[mldavis2]

I'd definitely set up an experiment to see if you can tell enough difference to make it worth the effort to pressurize with N2 or CO2. As I said before, it's my understanding that, although fresh roast gives off CO2, the beans do have small amounts of O2 in the cell matrix. You may eliminate outside O2 from entering and accelerating deterioration, but there isn't much you can do about what's already in the bean. We know that even vacuum packed roast gets stale.

Let us know how it turns out. I don't know of anyone trying pressure instead of vacuum.

[MileHiCoffeeGuy]

Agree with the other replies. It's not about "sucking out CO2" but rather, oxidation. That said, I am as much a fan of vacuum-packed roasted coffee as I am of holding brewed coffee in airpots. Sure, it works, especially in the short term. But it certainly does not halt staling/aging, and maybe more significantly, it sends the wrong message about coffee ... I mean, for me home roasting is as much about a new approach to coffee, treating it as a fresh and fragile food item, as it is about any particular technique to accomplish the result ... and that is, having small amounts of fresh-roasted coffee and enjoying it before all those fleeting volatile aromatics split the scene, and before O2 has a chance to stale the lipids, etc. Of course, same goes with new appraches to brewing and espresso as well. Can you imagine pulling a beautiful shot, then putting it in a mini thermos to enjoy a few hours later?

I have wondered if vacuum packing roasted beans would actually harm the beans by allowing the lipids to surface faster, thus being more exposed to oxidation; or conversely, allowing O2 to permeate the beans faster - as with using vacuum to marinate meat. Any comments Tom?

Also, what about storing our green beans under vacuum? I know SM does to some degree. I like to buy a lot of green beans at a time to cut down on shipping costs - Is vacuuming the beans of any further value?

[kaboodle]

Maybe I'm misunderstanding Tom's comments, but lots of homeroasters use vac-seal methods to store our roasts just as others would use the various products that Sweet Marias sells to store roasted coffee. It's as simple as that and has nothing to do with trying to "send a wrong message". What is the difference between using the Sweet Marias marketed products such as the de-gas bags or that "Coffee Tin"to attempt seal out oxygen vs a Foodsaver and a Mason jar? We don't all have the luxury of time to roast every few days and consume it such that no oxygen limiting storage methods are necessary.

Rick