There is even a less expensive than using Soda Stream or paint ball cartridges. Due to the uptake in micro-brewing you can get a decent sized proper canister filled with CO2 or Nitrogen at a local brew your own facility for under $15 bucks.
The initial cost may be higher but the long term cost would make up the difference.

ira wrote:I would assume, but don't know, that part of the reason the Coffee Freshness System works so well is because they flush the cylinder with CO2 before the final pressurization, otherwise all the oxygen that was there to begin with is still there. i.e., even with a sodastream, you'll need to make a hole in the bottle so the air(oxygen) is flushed out before you pressurize the bottle. Having never seen or used one I can't be sure, but they do use the word flush when describing how it works and it's easy to imagine why that would be necessary. In their system it might be perfectly reasonably to fit a blow off valve at the top and just pressurize till the pressure stabilizes and then add CO2 for another few seconds. If me recollection is correct, CO2 is heavy and then you'd want to fill from the bottom and exhaust out the top, exactly the opposite of a sodastream.

Ira

(Awakened brain cells long asleep with dreams of Avogadro's number....)

Correct if you were pressurizing the Sodastream bottle with CO2 (in which case the number of O2 molecules in the bottle stays the same - so that partial gas pressure for O2 would remain the same).

But:
1. Sodastream fills from about a 1/3rd from the top (otherwise the CO2 wouldn't dissolve as well in water - just pressurize the bottle).
2. Sodastream "burps" when you overfill it (as a safety mechanism).
3. "Burping" should "flush" some of the oxygen. But not all of it. I remember vaguely from school that partial molarities trigger diffusion - making it difficult (actually - it is impossible) to replace all oxygen with something else.
4. When you introduce CO2 into the air mixture, the partial pressure of CO2 increases (for O2 it stays the same). The burped air mixture (e.g. through a 1 way valve) has the partial pressure n of Oxygen (O2) as well as CO2. So the amount of O2 molecules will decrease by the ratio of the molars released (molar number of molecules - the "n" in PV=nRT)) vs. how many moles stayed. Every burp will drive the number 'n' for O2 down, reducing the partial pressure of Oxygen.

The concept of CO2 being heavier than air makes for nice reading but not really relevant in the microcosm of a bottle. No stratification or inversion layers in a bottle...http://physics.stackexchange.com/questi ... to-gravity

AssafL wrote: The concept of CO2 being heavier than air makes for nice reading but not really relevant in the microcosm of a bottle. No stratification or inversion layers in a bottle...http://physics.stackexchange.com/questi ... to-gravity

Yep, there will be mixing due to partial pressures/brownian motion and the movement of the container.
Don't let that get in the way of marketing for valve bags, though!

ira wrote:I would assume, but don't know, that part of the reason the Coffee Freshness System works so well is because they flush the cylinder with CO2 before the final pressurization, otherwise all the oxygen that was there to begin with is still there. i.e., even with a sodastream, you'll need to make a hole in the bottle so the air(oxygen) is flushed out before you pressurize the bottle. Having never seen or used one I can't be sure, but they do use the word flush when describing how it works and it's easy to imagine why that would be necessary. In their system it might be perfectly reasonably to fit a blow off valve at the top and just pressurize till the pressure stabilizes and then add CO2 for another few seconds. If me recollection is correct, CO2 is heavy and then you'd want to fill from the bottom and exhaust out the top, exactly the opposite of a sodastream.

Ira

This is why just pressurizing with an inert gas, any inert gas, is not effective. To reduce the residual O2 concentration to a sufficiently low level requires several pressurize-vent cycles. The CFS does this pressurize-vent cycling automatically. Each cycle is a pressurize to full pressure ~10psi and a vent to just above 0 psi.

I am operating this system from a 20 pound CO2 cylinder and they are easily exchanged at a local welding supply shop. Used 20 pound cylinders are also readily available. For the heavy coffee consumer the 20 pound cylinder is the way to go with this system. The justification for using CO2 is cost and availability, and it works just fine.

The normal gas diffusion solves the where to vent and where to fill issue. There is relatively complete mixing on each fill/pressurize cycle. This is demonstrated by analyzing the exhaust stream for O2 content with a gas analyzer. The velocity of the incoming CO2 is sufficient to provide very good mixing.

The CO2 evolved from roasted coffee is the byproduct of oxidation and continued oxidation leads directly to stale coffee. You do not want to rely on the coffee as a source of continued CO2.

The CFS reduces the residual O2 to ~1% for a full cylinder and ~2% empty cylinder.

Just got the external tank version of this. Super excited. I really think/hope this helps to fully realize the single-dosing dream of realistically keeping multiple beans in rotation without feeling like you have to hurry and finish them before they go stale.



Assuming all works as expected, I think I'll risk an order of Caffe Lusso that everyone is raving about. I'm normally hesitant to order west coast coffees unless they ship USPS priority, but I think this might open that up to me.

shawndo wrote:Assuming all works as expected, I think I'll risk an order of Caffe Lusso that everyone is raving about. I'm normally hesitant to order west coast coffees unless they ship USPS priority, but I think this might open that up to me.

I think they're rolling out with upgraded shipping options and 1 kilo options in less than 3 weeks.

shawndo wrote:Just got the external tank version of this. Super excited. I really think/hope this helps to fully realize the single-dosing dream of realistically keeping multiple beans in rotation without feeling like you have to hurry and finish them before they go stale.

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Assuming all works as expected, I think I'll risk an order of Caffe Lusso that everyone is raving about. I'm normally hesitant to order west coast coffees unless they ship USPS priority, but I think this might open that up to me.

Awesome! Look forward to your feedback on the system. Tom's review has had me considering it for a while now.

TomC wrote:I think they're rolling out with upgraded shipping options and 1 kilo options in less than 3 weeks.

Tom,

I had a thought when looking at the system. Could the single large container be used to store multiple beans somehow in the same cylinder? Dividing up the space with some kind of divider or non airtight trays? You could open the large container dose out several different doses of different beans from stacked trays, then put all the trays back inside and pressurize it.

The system would be perfect for me if I could store 3-4 beans in separate 500g containers somehow.

Bak Ta Lo wrote:Awesome! Look forward to your feedback on the system. Tom's review has had me considering it for a while now.

+1. I've also been considering this product for a while as well. It'll be nice to hear your feedback.

+1.

Seems like a good test is to take a day old roasted coffee, seal it and CO2 flush it. Take an identical amount, seal it in a bag and store both for a month. on the 29th day, buy another pound of freshly roasted coffee.

Test all three side by side. The best outcome is #1 and #3 cannot be distinguished and 2 is horrible.

BTW - why is the system pressurized? I thought the idea is to reduce the amount of oxygen by replacing it with CO2. Once the oxygen is out why do they need the pressure?