Freezing coffee beans for espresso - Page 2

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JohnB.
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#11: Post by JohnB. »

I started vacuum sealing/freezing my roasted coffee around 2008. Used Foodsaver bags back then but these days most of it goes into canning jars. Any coffee that is going to be in the freezer more then 1-2 weeks gets vacuum sealed. I've compared vac sealed to non vac sealed coffees a number of times over the years & the vacuum sealed coffees hold up much longer in the freezer. I keep a scale in the freezer room/pantry so I can pour my dose out of the jar & put it right back into the freezer. I've yet to see the much rumored condensation I read about in these threads but maybe one day. :D
The frozen/cold beans go directly into the grinder.
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JohnB.
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#12: Post by JohnB. »

Auctor wrote:
I think thawing changes the bean, and possibly ages it faster (similar to veggies). Also, definitely never freeze, thaw, and refreeze.
Are you saying you've had bad luck freezing vegetables?
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RyanJE

#13: Post by RyanJE »

I used to fuss with vac seal and freezing in jars. Now I just take over the one way valve and freeze before the bag is open. You'd be surprised how long the beans are still great and you take them out.

I think most people's "theories" about coffee age and problems with freezing etc. are based on obsession over the shot making process. That, and some coffee just isn't great before you even get it. It's hard to know all the variables like the harvest season, green storage, how it was handled and shipped as bulk green, processing at the farm, etc.
I drink two shots before I drink two shots, then I drink two more....

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Spitz.me

#14: Post by Spitz.me »

This topic gets revisited fairly often and the conclusion never changes, no matter the preoccupation/theory that spurred the thread. Countless home baristas are freezing coffees and have been for years.

James Hoffman mentioned that "it can't be good" to take the beans out of the freezer to dose and then replace them. Well, it hasn't been bad....
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GC7
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#15: Post by GC7 »

Freezing works very well to preserve flavors in roasted coffee. I leave beans for up to three months or so in valve bags with tape over the valve. I wait at least a day for the O2 to be displaced by out gassed CO2 and then freeze.

Freezing cells is something I know a bit about as we've done this in my labs for almost 50 years. It's only a concern if you want to freeze and then maintain viability and grow the frozen cells. Bacteria and the like are easy. Just add a bit of glycerol and put in liquid nitrogen or -80 freezer. For animal cells, you need DMSO and a more complicated freeze and then thaw protocol. The glycerol and DMSO prevent ice crystals from forming inside the cells and tis is what kills them and make things like meat or fish appears mushy after thawing. This doesn't apply so much with plant cells with cell walls and where roasting removes most of the water. Any minor change in grind settings (I don't see any difference) should not affect the extraction of preserved compounds that contribute to flavor.

Auctor

#16: Post by Auctor »

The trouble I often get into is that while I can observe things well enough, it's sometimes challenging to combine those observations with cogent explanations (which are themselves hypotheses). :lol:

Freezing temperatures can slow or stop certain chemical reactions that occur at room temp. I think we can agree with this. I also think we can agree that as a result, freezing can slow or even stop the "staling" of coffee. Finally, I think we can all agree that moisture (eg water vapor in the air) is bad for coffee beans.

Where I think there's disagreement is whether the freeze/thaw/refreeze cycle has any impact on coffee, especially when new air is introduced during the thaw phase. I used the example of a frozen veggie to claim that thawing and refreezing can be detrimental to coffee (like it is to veggies). But that analogy likely just confused the matter because veggies are primarily water-based and thus are more susceptible to damage during a freeze/thaw/refreeze. Sorry about that.

My contention is that the introduction of air (which includes both oxygen and water vapor) at any point once coffee is roasted is detrimental to the bean. Further, any freeze/thaw/refreeze would impact the beans, since there is water vapor in the beans. Hence my suggestions.

My experience over days of using the same beans and playing with different scenarios has led me to my conclusions. Whether others have experienced the flavor degradation I've tasted is subject to individual palates and their own quasi-science experiments to tease out the same results.

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Spitz.me

#17: Post by Spitz.me »

The cycle isn't freeze, thaw and then refreeze. The cycle is that we take the dose out and replace the coffee in the freezer. I don't describe my process as thawing all of my beans for each dose. I wouldn't define my frozen salmon piece as thawed because I took it out for a few seconds.

Those who have been freezing successfully for years aren't arguing, they're stating what is working and has worked for years.

The small amount of condensation hasn't seemed to worsen the coffee in the few seconds it takes to dose for many people. If it did, no one would be using the method. Taste is all that matters. We all do what works for us whether it's scientific or not.

Burrs haven't rusted either.
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Auctor

#18: Post by Auctor »

Spitz.me wrote:The cycle isn't freeze, thaw and then refreeze. The cycle is that we take the dose out and replace the coffee in the freezer.
I get it. And I think, based on the limited amount of exposure before the beans are put back in the freezer, I would agree, there's probably little risk to what you've described above. That said, the original post most definitely was not that scenario, and is what I originally commented on. See below.
pablodekaffe wrote:But today we pulled some shots on Decent Londinium profile with beans that had been frozen after one week of roasting, and only one week in freezer before thawing overnight, and the taste was really off.

We had pulled some shots with this coffee before freezing, and it was flavorful, but we pulled three shots today and although the shot profiles looked good, the taste was noticeably different, to the point of bitterness and unacceptable aftertaste.
It's the thawing overnight that I responded to.

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Spitz.me

#19: Post by Spitz.me »

Auctor wrote:I get it. And I think, based on the limited amount of exposure before the beans are put back in the freezer, I would agree, there's probably little risk to what you've described above. That said, the original post most definitely was not that scenario, and is what I originally commented on. See below.



It's the thawing overnight that I responded to.
Ahhh, thanks for pointing that out.

I would like to add that it's fairly clear, although not through rigorous testing, that the staling has effectively stopped. I can keep my grind level the same for the duration that those frozen beans exist. I also don't have to change my grind level if my attention is averted for a minute and I can't grind the beans right away. Grind level changes would give us pause for something drastically changing in the beans and I haven't felt compelled to change grind level significantly due to aging of the frozen beans.
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JohnB.
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#20: Post by JohnB. »

It takes about 10 minutes for a vacuum sealed bag (1/2 lb?) of coffee beans removed from the freezer & placed on a counter to come up to room temp in a 70* room. Timed it once using an infrared temp gun. When you leave a bag of beans out overnight it isn't thawing, it's staling. The roasted beans have so little moisture in them that they are mainly just cold, not frozen.
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