Grinding coffee beans stored in a frozen bean cellar without defrosting?

Grinders are one of the keys to exceptional espresso. Discuss them here.

#1: Post by boren »

My improvised "bean cellar" is a set of glass vials with cork caps and a plastic rack (everything bought from aliexpress for a total of 29 USD shipped). The caps don't have a one-way valve, so are likely to lose their seal if degassing continues and produces pressure. To avoid this I'm planning to store them in the freezer, where, as far as I know, degassing is supposed to completely stop. The idea is to then just take a vial out and grind the beans without defrosting. I figure if there's condensation when I open a vial it's not an issue, since it won't affect the other vials, and the very mildly wet beans to some degree mimic RDT.

Does this plan make sense? Any downside to grinding frozen beans? Searching this forum and the web it seems that not only is it not an issue, some even claim it improves taste.


#2: Post by gilbert »

Simpler to just try it! Been doing it for ages, I need to grind slightly coarser but otherwise all good

boren (original poster)

#3: Post by boren (original poster) »

@gilbert - are you using a freezer or the fridge? If the fridge is sufficient to avoid degassing pressure buildup I may prefer that, as it's more accessible. My freezer is located below the fridge, behind a door and split into two drawers. A bit of a hassle to get to stuff compared to the fridge.

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BaristaBoy E61

#4: Post by BaristaBoy E61 »

boren wrote:Any downside to grinding frozen beans?

Perhaps the biggest factor in grinding frozen beans might be if frozen too soon post roast that they might not have had sufficient time to degas and properly age to optimal taste.
"You didn't buy an Espresso Machine - You bought a Chemistry Set!"

boren (original poster)

#5: Post by boren (original poster) »

I plan to move the beans to storage 9 days after roasting, which is close to optimal in my experience. I use a Gene Cafe roaster, and ~9 days after roasting usually works well for both darker roasts (where it's the end of their "prime") and lighter ones (where it's the beginning). I normally roast to medium level, so it should be good.


#6: Post by jpender »

It's fine. There are numerous threads that discuss this. Even opening the same bag/container from the freezer repeatedly appears to be okay. There are reports that you have to adjust the grind slightly for cold beans. The condensation is typically a lot less additional moisture than what is necessary for RDT.

boren (original poster)

#7: Post by boren (original poster) »

Thanks for all the comments. I think I chose the wrong vials by going for ones that come with cork caps and therefore can easily lose their seal with some degassing pressure. I should have bought ones with screw caps. Live and learn I guess...


#8: Post by Rcus »

May I have some experience sharing here because I have been doing a similar process in these months.
I repack my coffee beans and put each portion, 15g, into a 6x8cm disposal zip bag. After repacking the beans, I put all the bags into a larger zip bag. I take out each portion inside the freezer without moving out the whole larger zip bag. I grind the beans and make coffee directly without defrosting. The temperature for pour over should be 4 degrees Celsius more to get similar results as unfrozen fresh beans.

The result is noticeably better than just putting beans in room temperature. (I keelpt frlew portion in room temperature for comparison) The beans can be kept more than 3 months with consistent quality in freezer.

Using cheap small zip bags to avoid cleaning and storing issues.


#9: Post by Jonk »

jpender wrote:Even opening the same bag/container from the freezer repeatedly appears to be okay.
It's curious, because for me there seems to be clear degradation or at least change in flavor doing this. I tried it a few years ago and have been giving it a new shot after reading these kinds of claims.. I have at least had more luck with thawing a few days' worth of beans at a time even if it means leaving them in a hopper.

I wonder if it has to do with what kind of freezer it is - mine's got "auto-defrost" and is not extremely cold, just put a thermometer in with the beans and they were only at -13C / 8F


#10: Post by jpender »

My freezer is the same.

I just finished a 12oz bag of coffee this morning. I rested it for 5-6 days and then put it into the freezer. It sat there, unopened, for about 2 1/2 weeks. Once opened, I put a rubber band around it and then put that in a ziplock. It took me a week and half to go through it. So that's taking it out of the freezer to get some beans and then putting it back in again, 2-3 times each morning for about 10 days. The last couple of shots I just had this morning were the best. Part of that is because it took me basically the whole bag to figure out what worked the best (doh!). But the coffee showed no sign of degradation.

I tried to do this more analytically several years ago. I assumed that degradation from repeatedly removing the beans from the freezer would be due to accumulated moisture. So I measured the moisture content of the beans as I went through the bag, taking it out of the freezer and then returning it. I also did blind taste tests, comparing the coffee I was exposing to the air each day with individual sealed doses of the same coffee. And what I found was that I could not tell which was which by taste. And the accumulated moisture was essentially nil. I repeated the whole thing a second time and got the same result. Maybe with a different coffee I would have tasted a difference.

I think that what happens with freezing coffee is not fully understood. Sometimes I don't like what comes out of the freezer but it isn't clear whether it's the coffee or the freezer that's the problem. I'd have to do a whole bunch of side by side blind tastings with many different coffees to figure it out. That's way too much work.