Ground coffee freshness question

[NTL2009]

TL;DR

What contributes to ground coffee losing freshness, and what can be done about it?

Somewhat separate from the coffee advice of “buy whole beans, grind fresh at home daily”, I'm looking to understand the factors that contribute to purchased ground coffee losing freshness after opening (oxygen, humidity, temperature, time, other?). I'm assuming oxidation is the main factor, assuming normal room temperature and mid-range humidity.

It appears (I'm having trouble finding good info on this) that a high quality modern pre-ground coffee is packaged in a way that maintains 'reasonable' freshness for months(?) if unopened. I think that little button on the package was a key development - that is a one-way valve, and freshly roasted and ground coffee out gasses CO2. That valve allows for packaging fresh roasted/ground coffee (under vacuum?), and the CO2 can escape w/o blowing open the package. I think that being bathed in CO2 with very little entrapped air keeps the ground beans fresh in the package.

So my question is, how to maintain that freshness once opened? Some coffee 'experts' claim that once ground, flavor degrades in just a few days. I can't say I really notice this to any great extent (a 12 oz bag lasts me ~ one week), but I'm not doing A-B comparisons. Still, I'd like to use 'best practices' if it doesn't entail too much extra effort.

There are many suggestions out there. The most reasonable sounding to me are the piston/cylinder style containers. Put the ground coffee in the cylinder container, the lid/piston/seal is pushed down and a one way valve lets air escape, eliminating the head-space in the container. Some of these are used in conjunction with a vacuum system to remove more air. But it needs to be opened again each time you brew. This is where I need some help:

It seems that just opening and pouring the grounds into that container expose all that surface area of the grounds to air. And there is some air space between the grounds. Is that enough air, even with no head-space, to promote staling of the coffee? Is there enough air 'clinging' to the ground coffee to stale it? Or would it take a larger volume of air to stale an amount of ground coffee?

I think about this whenever I put some food into a zip-lock style bag. It is suggested to remove as much air as possible, but if it only takes a little air to stale a piece of bread, am I wasting my time trying to get most of the air out? Is only a vacuum seal really going to make a difference in practice?

I'm no chemist, but I guess I'm thinking in terms of a reaction formula. How much air, compared to the coffee, is required for the staling action?

Recently, I've just been opening a 1” slit in the bag, and I try to pour out my daily grind in more of a toothpaste tube fashion, direct from that bag. Pushing from the bottom, so very little air enters the original package, and I'm not pouring the whole package into another container, and therefore not exposing all those contents to air. I then seal the bag with a clip, and put the bag in an airtight container.

Thoughts?

 

[berkeman]

I did a Google search on starbucks ground coffee bag one-way valve (my current brand of coffee), and got to this page:

https://www.starbucks.co.id/coffee/learn/coffee-faqs

What’s the best way to store coffee? How long will it stay fresh?​

Once roasted, coffee begins to lose its flavor the longer it’s exposed to air and moisture. We recommend that you store it in an airtight container in a cool, dark place and grinding it just before brewing. Coffee in an unopened FlavorLock™ bag will stay fresh for several months.

What is a FlavorLock™ bag?​

Our unique FlavorLock™ technology uses a special one-way valve that allows the carbon dioxide released by freshly roasted coffee beans to escape a sealed coffee bag without allowing flavor-robbing oxygen to get in. All Starbucks coffee is sealed in our airtight FlavorLock™ bags within two hours of roasting so that it stays fresh until you’re ready to use it.

 

[symbolipoint]

Nice Question and Interest.
No matter how well packaged some commercial (and popular) are, something I had still found was that (1) they still tasted dull or flat or muddy and (2) they were still overly-roasted. That is not exactly what kind of response you're hoping for. This is why getting hi-qual green unroasted beans and roasting them yourself, is still much better option. I again unlike what you want, store the beans in small glass jars, as whole beans; and only grind as much as I brew as I go. Result is, FRESH for more than about 2 weeks.

 

[JT Smith]

I think it's a combination of oxidation and volatilization that causes coffee to degrade. Obviously it will happen faster to ground coffee versus whole beans. And the finer the grind the faster the degradation. To stop oxidation you could remove the oxygen. A vacuum pump could do that but you might also be removing volatiles that way. The other approach is to displace the oxygen with an inert gas. There is a commercially available home system for doing just that. It's expensive and bulky and so not practical for most people but it does work. Volatilization still happens though. The only way to stop that is to reduce the temperature.

A lower temperature also inhibits oxidation so one approach to maintaining freshness is to lower the temperature as far as you can. Just going by the Arrhenius equation you would expect to slow things down quite a bit by using a normal household freezer. Of course you have to get the coffee out of the freezer to use it so some thought has to go into exactly how it's stored and removed. Some people partition a batch of coffee into smaller sealed parcels so that they are only opening a little bit at a time.

Whole beans are much better for storage but you can apply the same logic to ground coffee as long as your expectations are lowered.

Coffee is getting increasingly expensive. Maybe tea is a better choice?

 

[NTL2009]

... This is why getting hi-qual green unroasted beans and roasting them yourself, is still much better option. ...

This will be a bit off the main subject, but another consideration I have here is the quality of home grinders. I know the advice is for burr grinders, but from what I've read, the sub $200 burr grinders give pretty inconsistent grinds. My thought is is that I *may* be better with consistently ground pre-ground coffee, compared to a poorly home ground, but fresher from whole beans. I'm not going to spend $500 on a coffee grinder, or do it manually.

I bought a cheap, but decent reviews at the time, burr grinder. The grind was way different from the pre-ground I buy. Lots of dust, chunks of different sizes. I may try again, but I think the over-extraction from the dust, and the under-extraction from the larger chunks made a worse cup of coffee than my pre-ground (and a 12 oz bag is only open ~ 5 ~ 6 days).

 

[NTL2009]

I think it's a combination of oxidation and volatilization that causes coffee to degrade. Obviously it will happen faster to ground coffee versus whole beans. And the finer the grind the faster the degradation. To stop oxidation you could remove the oxygen. A vacuum pump could do that but you might also be removing volatiles that way. The other approach is to displace the oxygen with an inert gas. There is a commercially available home system for doing just that. It's expensive and bulky and so not practical for most people but it does work. Volatilization still happens though. The only way to stop that is to reduce the temperature.

A lower temperature also inhibits oxidation so one approach to maintaining freshness is to lower the temperature as far as you can. Just going by the Arrhenius equation you would expect to slow things down quite a bit by using a normal household freezer. Of course you have to get the coffee out of the freezer to use it so some thought has to go into exactly how it's stored and removed. Some people partition a batch of coffee into smaller sealed parcels so that they are only opening a little bit at a time.

Whole beans are much better for storage but you can apply the same logic to ground coffee as long as your expectations are lowered.

Coffee is getting increasingly expensive. Maybe tea is a better choice?

I do have a vacuum system (used to transfer and de-gas home-made wine) that I maybe could adapt to this - but the question of stripping volatiles is an interesting consideration, and it would be a bit awkward.

I also have a supply of inert gas (CO2 for my beer kegging system). And I have used that for some longer term storage of some things, but it's a little awkward for daily use.

Hah! I picture myself with one of those containment chambers with the rubber gloves - put the coffee in there with 6 small containers, flood the chamber with CO2, and weigh/fill the containers in that inert environment, and then seal them for daily use. :) Nope, not going that far!

The problem with freezing for short term is, you need to pull them and let them warm to room temperature before you open them, or you'll get condensation on them. As you say, and similar to above, if I prefilled containers with a daily dose, and pulled one each morning, it would be opened and used right away. Or left out overnight to get to room temp, would be minimal time at higher temps. But I'm not sure this matters for the max of ~ 6 days I'd need to store them.

And while the 'experts' all seem to be in agreement that just a few days affects the flavor, I'm not convinced that my perception is that discerning anyhow. I'm probably going to continue with what I started doing recently - make a small opening in the bag, kind of squeeze it out like a toothpaste tube to reduce air ingress, then clamp it and put it in an airtight container. That's probably good enough, but I'm open to improvements.

 

[symbolipoint]

Coffee is getting increasingly expensive. Maybe tea is a better choice?

But they are not the same. Too different in important ways. Difficult to explain!

 

[symbolipoint]

The mention and commenting about grinders --
I use either of two grinders. One is the typical electric with the clear plastic top cover and the flat with end-fins. It works. Noisy but I can use time measure to learn how to control grind size. Maybe it cost $15 when bought about 15 to 20 years ago. Top cover has breaks in it but the whole device still works. Other grinder is a very cheap, ~$15 I bought through Amazon: I have no idea the brand or the company but is a small manual burr grinder, and has an adjustment knob below the burr part. It can produce a fairly undeniable fine grind.

You do NOT have to spend more than 30 dollars for a very very acceptable coffee grinder.

One thing about my small manual grinder - need to turn the crank for between one minute, and one and a half minutes to grind 1 tablespoon of coffee beans. Note I spent about $15 for it; there ARE better manual grinders (and higher in price).

 

[256bits]

I had some beans, old and hard, and thought of making my own grinder as that seemed to be the way to do it as per the advice given on all the coffee sites - grinding that is. The electric grinders on sale all seemed cheap in quality and I am sure end up as just another useless gadget for the kitchen. I would never go electric, but manual anyways. some specialty shop might gave a good machine.

Instead I opted to roll the beans. It takes a while for old, dry beans.

Shinier, newer beans roll more easily.
Here is the ground beans, the plastic bag that does not split, and the rolling wheel ( 4-inch dia x 2, with a slight curve on the surface ).
One(1) minute and I am ready to brew.

Zero Dollar Investment.

 

[JT Smith]

But I'm not sure this matters for the max of ~ 6 days I'd need to store them.

Probably not. For most people and most coffees it's enough to simply close it up in the bag it came in if it's just for a week. That's if it's whole beans. Ground coffee will change much more quickly. But if you start with stale coffee then it doesn't matter as much. If you buy mediocre stale coffee and avoid developing a taste for the better stuff you won't care that it's stale.