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snwcmpr
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storing roasted beans
ChicagoJohn
Just over six months have passed now since I started the experiment described above in mid-November. To summarize, I obtained a sufficient quantity of my favorite coffee -- a Yirgacheffe from FreshGround Roasting, a local roaster -- and I roasted some immediately using my standard Scott Rao profile, mixed the 91 gram batches thoroughly, vacuum sealed half and put in a deep freeze along with a quantity of greens also vacuum sealed. The deep freeze is at -5F / -20C. I then prepared and consumed the new roast for about two weeks using my standard Aeropress infusion method. That experience was the great, full spectrum taste, flavor and aroma I've become accustomed to and love.

So yesterday was six months and one week after placing the greens and roasted beans in the deep freeze. I let them sit in the package overnight to come back to ambient temperature without exposure to air. One thing I noticed right away was that the roasted beans looked as if they had not been vacuum sealed -- there was a fair amount of gas in the bag and the beans were free-flowing, not a solid brick like the greens were. The bag remained tightly sealed, so the only explanation is off-gassing from the roasted beans even though they were allowed to stand for days after roasting before vacuum sealing.

While I had initially devised a complex rating form for various aspects of subjective experience in consuming the coffee, I realized that the time lag would invalidate the meaning of this. So instead, in preparation for today, I have drunk the Yirgacheffe for a month roasted as I went along from a recent two-pound purchase from FreshGround. I ran out yesterday and today I transitioned over to the six-month old roasted beans that had been stored in the freezer.

I could detect absolutely no difference. The coffee was as great as it usually is. Had the gas in the bag been oxygen, I'm doubtful this would have been the case. In any event, I found this result to be encouraging. I will continue to drink the remainder of this roast and then transition in to a new roast from the vacuum sealed greens. However, with this result from the roasted beans, I would certainly not expect to see any adverse effects of storing the greens vacuum sealed and deep frozen.

Assuming that this result can be generalized to other bean varieties (a reasonable assumption I would think) t\e practical significance of this experiment for me as a consumer of only about 30 gm of roasted beans per day is that I can purchase in quantities that will be cost effective and at the best time without concern for the effects of aging (of the beans; unfortunately not for me personally).

So I just wanted to provide this update for now, and I'll add to the results in a few weeks after I've worked my way through the stored roast and the newly roasted stored greens.
So many beans; so little time....
 
snwcmpr
Waking Life Espresso, a shop no longer in Asheville, NC, brewed some Finca Kilimanjaro Gesha some years ago. Spectacular brew. Roasted by Mountain Air Roasting, a member here.
Some time later, no idea, they brought out some frozen, vacuum sealed, 5 lb bags. Spectacular brew again.
That is my only experience with frozen vacuum sealed coffee.

I vacuum seal batches, 1 lb green weight, for road trips and vacations. Other than that, I roast as I need.

Ken in NC
--------------
Backwoods Roaster
"I wish I could taste as well as I wish I could roast."

As Abraham Lincoln said "Do not trust everything you read on the internet".
 
oldgearhead
Coffee doesn't last long enough around our house to ever consider storage. I roast 2 kilograms a week, just for my wife, myself, and a few friends on the weekend. Heavens, I consume 500g per week by myself...
No oil on my beans...
 
JETROASTER
Thanks for posting your results. I came across this patent a few weeks ago;
https://www.googl.../US3725076 It seems to suggest that grinding while frozen keeps the oils in a state that retards the loss of aromatics....thereby giving better shelf-life than coffees ground above freezing.
I believe it was also this patent (perhaps one of the links) that asserted beans frozen immediately after roasting maintained freshness longer than the unfrozen....even if all were subsequently stored at room temp. The idea being that simply freezing for a short period of time after roasting creates a product with a longer shelf life.
Cool research. Thanks for sharing. Cheers, -Scott
 
ChicagoJohn
That is interesting information, Scott, and since the volatility of many of the hundreds of chemicals in roast coffee affecting aroma and flavor is a function of temperature, the concept makes sense. It is also a function of time, and so the longer the delay between grinding and infusion, the greater the loss, especially in the more volatile compounds.

The other issue, however is that of exposure of cold surfaces to warmer ambient conditions. The solubility of water in air increases with temperature, and if cold bean surfaces are exposed to warmer air with moderate to high humidity, condensation will take place -- not a problem if the beans are ground and infused immediately, but if a container of frozen beans is repeatedly opened in a warm humid environment and then returned to the freezer, the introduction of both moisture and oxygen could, in theory, cause undesirable changes affecting cup quality. When I remove beans from the deep freeze, I always allow them to remain at ambient conditions over night before opening the package thus eliminating the temperature gradient.

I neglected to mention related considerations involved in my experiment. First, I used Foodsaver Heat-Seal vacuum seal bags. They are made of five layers of high density polyethylene film with a nylon film outer layer for strength and rigidity. Food bags meant for short-term use may be 1.5 - 3 mils thick whereas the overall thickness of the bags I used is about 14 mils, and thickness is one of the determinants of permeability to moisture and oxygen.

Another factor is orientation of crystalline sites within the film since permeation occurs between these sites. Because of this factor and also the occurrence of microscopic pinholes, single layer films tend to be more permeable than multi-layer films at equivalent total thickness because the permeation path is more circuitous and because it is unlikely that pinholes with align, and permeability to oxygen and water vapor are highly correlated in these films.

Another is polymer density; low density polyethylene is about 8 - 10 times more permeable than high density polyethylene. All polyethylene films are quite permeable to aromatic organics; nylon is an effective permeation barrier for these compounds.

Drawing a strong vacuum on the beans initially is important, of course, in minimizing the initial oxygen and moisture content.

So I thought I'd detail these conditions of my experiment because the results might be quite different if, for example, one were to substitute Zip-Lock storage bags for the FoodSaver Heat Seal vacuum bags I used.
So many beans; so little time....
 
alext
Great experiment and thanks for sharing it. Since there are 2 factors involved, vacuum sealing and freezing I wonder how much one or the other contributes.
 
ChicagoJohn
alext wrote:

Great experiment and thanks for sharing it. Since there are 2 factors involved, vacuum sealing and freezing I wonder how much one or the other contributes.


Good question, and there are many others that could be pursued; effects of type of storage container, materials of construction, vacuum vs air vs nitrogen or carbon dioxide, storage temperature, interaction of storage temperature and the previous parameter values, and so on.

My interest, however, is in solving a practical problem; that being how to get through extended periods of time when it is impractical for me to roast due to inclement weather conditions -- primary in the winter months. From my background as a chemist, I thought it reasonable to assume that reducing temperature would favorably affect chemical reaction rates; a rule of thumb for 1st order reaction kinetics is a doubling of rate for every 10C increase in temperature, so going from 23C down to -4C might slow any reactions to about 1/7 of what they would be at room temperature.

At the same time, reactant concentrations also affect rates, so reducing oxygen availability by vacuum, should be advantageous - flushing with nitrogen or carbon dioxide even better, but I didn't have that option. In a freezer situation where there is sufficient head apace in the container, ice crystals can vaporize (sublime) and condense on container surfaces, a phenomenon that is often evident when opening packages of vegetables that have been a freezer for a long time. So minimizing air space by drawing a vacuum should be helpful in minimizing this effect as well.

So my objective was to see if this combination of storage conditions would provide a way to solve this problem I have of winter weather here in Chicagoland given my admittedly undeveloped palate when it comes to coffee. (But since I am the only consumer of the product, my perception is the sole criterion.)

Having just finished the stored beans I roasted over six months ago, right after a month's daily consumption of freshly roasted beans of the same variety, I could detect no difference at all, even though I did see evidence of some out-gassing in the roasted bean pouch during storage. I just roasted the green beans today, and would expect to see no differences there either since I followed the same roasting protocol, But if I do, I'll report it here. Otherwise I consider this a success and plan to roast enough late this year to last me through the winter.
So many beans; so little time....
 
alext
I have a similar need. Since I roast outside, even in the mild northern california climate there are still winter days where its too rainy (if we are lucky) or a little too cold, so having an emergency supply stored is very appealing. I have limited freezer space so I wonder how long I can get away with storing at room temperature but vacuum packing. I might have to try it out. Put one bag in the freezer and one in a cabinet.

Thanks again for sharing your experiment and comments.
 
ChicagoJohn
alext wrote:

I have a similar need. Since I roast outside, even in the mild northern california climate there are still winter days where its too rainy (if we are lucky) or a little too cold, so having an emergency supply stored is very appealing. I have limited freezer space so I wonder how long I can get away with storing at room temperature but vacuum packing. I might have to try it out. Put one bag in the freezer and one in a cabinet.

Thanks again for sharing your experiment and comments.


Applying the rule-of-thumb dependence of reaction rate on temperature, I was unable to detect any difference at all in the roasted beans after six months at -4F (-20C) A typical refrigerator is around 40F which is about 4C.

So if you were to store the same type of Foodsaver vacuum seal bag of roasted beans refrigerator instead of the freezer, assuming a 23C (73F) average ambient temperature, then whereas in my freezer reaction rates wee would have been slowed down to 1/16 what it would have been at ambient, in a refrigerator it would still be slowed down to 1/4 what it would be at room temperature. This assumes, again, that the various reactions follow the rule-of-thumb model.

In other words, in a refrigerator after about six weeks would yield the same result as a deep freeze after six months insofar as any chemical reactions that might occur and which follow the model are concerned.

As you point out, however, we don't know the relative contributions of temperature and of minimizing oxygen and head space. The experiment you outlined would perhaps shed some light on that, and I would look forward to hearing your results. If a six week storage interval is good enough to resolve your weather problem, then perhaps you could simply use your refrigerator which may have more available space.

I would also be interested to learn whether your roasted beans outgas like mine did even though I allowed them to stand for a considerable time (I can't recall now exactly what that was but I may have recorded it earlier in this thread). They were free flowing in the sealed bag while the green beans were a solid brick just like when I put them in. I've heard they give off carbon dioxide, but whatever the gas is, it's not oxygen and not going to react chemically with the beans since they expelled it.

I hope you learn that the vacuum sealing is sufficient alone. That would make things a lot easier.
Edited by ChicagoJohn on 05/29/2016 12:06 PM
So many beans; so little time....
 
alext
I just roasted today and also played around with the vacuum packer. Its the Frisper system and its ok. It doesn't use bag space that efficiently but the bags are reusable, so I guess its decent.

For the test, I will leave the roasted beans out 24 hours and then vacuum pack them. 1 bag in the fridge and one in a drawer at room temp. In 6 weeks I'll compare. Does that sound like about the right experiment?

Added: One thing I just thought of - before and after weights. This could be a good clue about moisture changes assuming precise enough scale.
Edited by alext on 05/29/2016 1:48 PM
 
ChicagoJohn
alext wrote:

I just roasted today and also played around with the vacuum packer. Its the Frisper system and its ok. It doesn't use bag space that efficiently but the bags are reusable, so I guess its decent.

For the test, I will leave the roasted beans out 24 hours and then vacuum pack them. 1 bag in the fridge and one in a drawer at room temp. In 6 weeks I'll compare. Does that sound like about the right experiment?

Added: One thing I just thought of - before and after weights. This could be a good clue about moisture changes assuming precise enough scale.


Before and after weights is an excellent idea -- wish I'd thought of that. When you reweigh the bags, make sure they have been out several hours so they have returned to ambient temperature -- weighing something hotter or colder than ambient can create convection currents in the air that affect the scale readings.

In my experience, it takes several days up to a week for roasted beans to sort of level off. I can definitely discern changes in flavor from 24 hours to a week. You might want to wait several days after roasting so that anything ordinarily happening in this interval doesn't interact with differences in storage temperature. I think I let my roasted beans sit for a week and then mixed them up before bagging and sealing.

Also, you might want to set the time at whatever time interval you think would work for your weather situation -- maybe two months, if you think you could get through your cold, rainy weather in that time, or even a bit longer. What we don't know is if, in my experiment, the roasted beans would still have been good at two years. So if you extend yours beyond what is pretty certain to be good in the fridge, say 2-3 months and everything is still good, then that would answer our questions regarding the practical issue of how to circumvent inclement weather.

Finally, I'll be great to see what results you get with different bags and a different vacuum sealing system. That will help us understand how important, if at all, that aspect may be.

I think it's great that you're interested in doing this, and I'm really looking forward to your results. It would be so much more convenient if this only required vacuum packing or at least vacuum packing and refrigerator storage versus a deep freeze.

PS - remember to allow beans to stand overnight at ambient after removing from any cold environment before breaking the seal to prevent moisture from the air from condensing on them.
So many beans; so little time....
 
alext
Welp for better or worse, I sealed the bags after 24 hours (5/30) of sitting in an open bag. Part of that was simply practical reasons but its also the point that I would prefer to keep the beans at.

I sealed 4 bags and put 2 in a drawer at room temp and 2 in the refrigerator. I decided to do 4 bags, so that I could try them at 6 week and then some later point. 60g of roasted beans in each.

Interesting thing, after 24 hours, 5/31:

Bag 1 (room temp): Brick, just like after vacuum packing.
Bag 2 (room temp): Some inflation. Not enough the beans can move but its soft and not brick like. Seems to be perfectly sealed.
Bag 3 (refrigerator): Brick, just like after vacuum packing.
Bag 4 (refrigerator): Some inflation! Nearly identical to bag 2.

The inflation in both bags seems to be around the bean mass and not the seals, so I am not sure what to say. I will continue to monitor.
 
alext
Update: 6/17
Start date: 5/30
4 bags vacuum packed after 24 hours rest, 60g of roasted beans in each

Bag 1 (room temp): Soft brick, not flowing. Slight change from last check.
Bag 2 (room temp): Some inflation. Beans now can move freely. Slight change from last check.
Bag 3 (refrigerator): Brick, just like after vacuum packing. No change from last check.
Bag 4 (refrigerator): Some inflation! Not as much as bag 2 above. No change from last check.

Its clear off-gassing is happening faster with the room temp bags. Curious to see variation between bags in each environment - not sure if its the beans of the bags. Once I hit about 6 weeks, I'll be opening all 4 bags and comparing to see if there are differences. That will be a high caffeination day :)
 
snwcmpr
I am going to make a guess.
The vacuum is not required. The off-gassing will not noticeably alter the taste. That the effects of oxygen (room air) would make a much more noticeable taste difference.
This is much like storing in a container with a one-way valve. Room air is pushed out by the off-gassing.

Another comparison might be a one-way valved container vs the vacuum. Would the vacuum withdraw more flavor, by pulling the gas out, than the canister, which would have a neutral pressure effect on the beans.

I vacuum seal for vacations, and I always have loose beans in the bags, some even after a week of so.

Ken in NC
--------------
Backwoods Roaster
"I wish I could taste as well as I wish I could roast."

As Abraham Lincoln said "Do not trust everything you read on the internet".
 
ChicagoJohn
I'm sure that's right. My green beans remained a solid brick and the roasted ones were loose due to outgasing even after allowing them to stand a week before vacuum sealing. The gases that come off would not include oxygen, as you said, and that is what is reactive.

As for the effect of temperature, I store roasted beans in bags with one-way valves, but I do notice changes with age. To the extent that non-oxygen related reactions occur over time, lower temperatures would be beneficial in slowing their rates. The longer-term outgasing could be due to volatilizing of low molecular weight compounds trapped inside the bean and/or the products of continuing chemical reactions.

This Fall I plan to roast, seal and freeze 15 lb to last me from December until March. I will store at least one pound at ambient temperature, try that at the end, and see whether there is any noticeable difference (to my uneducated palate, anyway :) That may help to answer the question of whether reduction in storage temperature is a meaningful factor.
Edited by JackH on 06/25/2016 11:52 PM
So many beans; so little time....
 
alext
Well the bags in the store even from the quality local brands never taste fresh to me. I assume they are simply relying on off gassing.

Do any commercial offerings use nitrogen? If nitrogen is cheap enough for chips I can't see why it couldn't be used for coffee as well. Unless of course it doesn't help...
 
ChicagoJohn
Good idea, and actually I believe nitrogen flushing has been used with coffee for this purpose. Any gas that replaces oxygen, such as nitrogen or carbon dioxide, would be beneficial in reducing oxidation rates. But there are two issues; one is ensuring that the interstitial void volume, not just the container head space, is flushed, and another is permeability of the packaging material to oxygen. Most polymers are subject to oxygen permeation via molecular diffusion and/or pinholes and other "leaks". So a thick layer or a continuous metal foil layer might be necessary. But achieving an optimum result could be costly in relation to the competitively pricing the coffee.
Edited by JackH on 06/25/2016 11:51 PM
So many beans; so little time....
 
gadget
Illy does package its coffee with presurizes nitrogen. They patented it so thats probably why other coffee brands cannot do this.

http://www.illy.c.../packaging
Edited by JETROASTER on 06/23/2016 10:08 AM
 
ChicagoJohn
It is interesting that a patent was issued for this because it is a method that is commonly used in storage situations where the presence of oxygen is detrimental. Unless the patent has other unique claims, such as a particular package design or sealing method, I would have thought the mere use of nitrogen or other relatively inert gas, such as carbon dioxide, would have been considered to be obvious and/or prior art and thus not patent-worthy. But these days the US Patent Office is happy to take applicants' money and often issue patents which are subsequently not upheld in court when an infringement suit is filed.
Edited by JackH on 06/25/2016 11:50 PM
So many beans; so little time....
 
gadget
I found this patent and it is very specific to coffee beans. It describes their complete process from after the beans are roasted until they are canned...

http://patents.ju...nt/4748030
Edited by JackH on 06/25/2016 11:50 PM
 
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