Due to the recent disaster I encountered because I froze my greens (link here), I placed several greens orders to replenish my stash. While they are on their way, I've been thinking about what could possibly be the safest method for preserving my new greens:

- I'll vac-seal in FoodSaver bags because I've had greens dry on me before in a very short period of time.

- I'll store them in a cooler @ room temp because freezing is out (this is why) and a cooler is dark and doesn't expose the bags to fast temp swings.

- I'm thinking about throwing in an Oxygen absorber inside the vac-sealed bags. Is this a good idea in theroy? I assume no one had tried this before so I'm not expecting verified answers, just intelligent thoughts

You know Ed, I'm starting to believe that these FoodSaver bags are allowing too much moister and O2 travel between the beans and the outer environment, and that's the reason long-term food storage geeks use Mylar bags instead. I'm now seriously considering the PAKVF4C Mylar bags from Sorbent because of their stronger protection against moisture and oxygen.

Lets keep in mind that you are the only one experiencing this issue. If the Foodsaver bags were allowing moisture in or out they would also allow air in & lose their vacuum. They are designed to keep air out & moisture in.

I'm pulling shots today from some home roasted Brazil greens that I bought back in early 2009. The greens have been vac bagged & frozen since that time and have lost nothing. Your fridge/freezer is a lousy long term storage solution but that still doesn't explain the rapid change in your greens. I keep mine in a dedicated storage freezer set to -5*F or lower. Most of the greens I roast have been vac bagged & frozen for a year or longer & I'm not experiencing your problems. I have no idea what happened to your greens but if the Foodsaver bags held the vacuum they are not the cause.

Bags do NOT stop O2/moister from passing, but they do slow the rate of transfer. Here's the data I found:


Food vacuum bags:
WATER VAPOR TRANSMISSION RATE 0.03 gr/100 in2/24 hrs.
O2 TRANSMISSION RATE 0.03 cc/100 in2/24 hrs


PAKVF4C Mylar bags:
WATERVAPOR TRANSMISSION RATE 0.0006 gr/100 in2/24 hrs.
O2 TRANSMISSION RATE 0.0006 cc/100 in2/24 hrs.


So, a 5"x10" 2"x4" food vacuum bag will transmit 1cc of O2 in a month, but it would take the above Mylar bag 4.5 years to transmit the same amount of O2....if my calculator wasn't fooling me.

I suck at physics so I won't pretend I know what the implications of this are; one thing for sure though: FoodSaver bags are not 100% O2/moister barriers. Now why is it not affecting you too, nobody knows so far.

I suck at physics also but I can tell you that I've got vac bagged greens in my freezer that are still sealed as tight as the day I put them there over 2 years ago. If that 1% per month figure was accurate these same bags would have lost their tight vacuum seal ages ago.

JohnB. wrote:If that 1% per month figure was accurate these same bags would have lost their tight vacuum seal ages ago.

Not necessarily, maybe. Let's hope someone who can understand what these numbers mean will chime in and save us from ourselves . BTW, it isn't 1%, it is 1cc (cubic centimeter)/month for a 5"x10" 2"x4" food vacuum bag; for bigger bags, the rate of transfer will be higher.

Considering that your original problem showed up after only 3 weeks in the freezer do you really think that caused your problems?

Where did you find the bag data?

farmroast wrote::lol: I'm also working on some early '09 Brazil, the Fazenda de Serrado. Pulled shots blended with some of the Tchembe yesterday and am just having a pour-over cup as I type.

Same one I just roasted, Carmo de Minas - Fazenda de Serrado??

John,
Do you try to roast the beans asap once back to room temp. from frozen?
Just a guess but I could see a possibility of something funky happening from disturbed moisture in the bean if kept in the bag too long after thawing.

No I don't. I'll usually pull out 4-5 bags at a time & roast them over the next 2-3 days but sometimes they will sit out for a week or more before I open the bag. I haven't noticed any difference in the way the greens smell or look pre & post freezing & I always check.