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.

 

[Mark44]

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

Well, hardly. As already mentioned, they are different things. Coffee I prefer; tea, not so much.

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.

We have an electric coffee grinder, but neither my wife or I ever use it. I makes a lot of noise, for one thing, and for another, doesn't grind the beans as fine. About once a month, I go down to my local Starbucks and get a pound bag of beans, and ask them to grind it at #5 on their machine.

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.

Do you use 1 Tbsp for a cup of coffee? That seems pretty weak to me. I use a small cup that says 1/4 cup (it's really a bit less than that), and put in that much coffee to make a cup. I have only one cup of coffee a day.

 

[symbolipoint]

Do you use 1 Tbsp for a cup of coffee? That seems pretty weak to me. I use a small cup that says 1/4 cup (it's really a bit less than that), and put in that much coffee to make a cup. I have only one cup of coffee a day.

Yes, or about that result. Brew volume seems to be between 8 and 10 fluid ounces, but I could or might do a recheck. The beans quantity I use is 1 tablespoon. Note also, I now use AeroPress for making the brew. The brew result is not weak.

 

[Mark44]

The brew result is not weak.

You and I might have different definitions for what constitutes weak coffee...

 

[symbolipoint]

You and I might have different definitions for what constitutes weak coffee...

How can you be sure? Grind size is also important. IF you often use AeroPress, tell me how much beans you use and how much water volume you use, and tell me what strength the brew is for you. I could try to do as you do and I could compare. Again know that I make a fine grind, although I have no way to measure this.

 

[Mark44]

How can you be sure?

You said you use 1 Tbsp of coffee beans and 8 - 10 oz of water. I use a bit less than 1/4 cup of ground coffee and 8 oz of water. The amount of ground coffee I use to make a cup is about 3 1/2 Tbsp.

IF you often use AeroPress, tell me how much beans you use and how much water volume you use, and tell me what strength the brew is for you.

I don't use AeroPress. As far as how strong it is, when I'm stirring the coffee I can't leave the silver spoon in it too long or else it would dissolve.

 

[symbolipoint]

You said you use 1 Tbsp of coffee beans and 8 - 10 oz of water. I use a bit less than 1/4 cup of ground coffee and 8 oz of water. The amount of ground coffee I use to make a cup is about 3 1/2 Tbsp.

I don't use AeroPress. As far as how strong it is, when I'm stirring the coffee I can't leave the silver spoon in it too long or else it would dissolve.

You seem to like very strong coffee. By any chance do you try to come up with a brew to be like espresso?

I'm running low on beans I have currently. Soon I plan to buy more and I may try making a pour-over brew. I would likely not go up to quarter tablespoon of beans, but more like one-and-half tablespoon of beans. Then could check the volume as the brew drips through.

Not sure if you do or can measure, but still curious: For your brewing, how is the grind?

 

[Mark44]

You seem to like very strong coffee. By any chance do you try to come up with a brew to be like espresso?

It's not quite as strong as expresso. I almost never have coffee at restaurants because it always seems so weak to me.

I would likely not go up to quarter tablespoon of beans, but more like one-and-half tablespoon of beans.

I think you meant a quarter cup of beans.

Not sure if you do or can measure, but still curious: For your brewing, how is the grind?

It's pretty fine. I always have the girls at Starbucks grind it at #5 on their machine.

 

[symbolipoint]

I think you meant a quarter cup of beans.

Right. I did mean one quarter cup of beans (that I would not go upto).

 

[symbolipoint]

It's pretty fine. I always have the girls at Starbucks grind it at #5 on their machine.

I make a fine grind in either of two ways:
(1) The small electric coffee grinder, 1 tblspn beans, grind continuously for 35 to 40 seconds
(2) The small manual burr grinder, 1 tblspn beans, I set the knob to one notch below fully tight.

 

[JT Smith]

Yes, or about that result. Brew volume seems to be between 8 and 10 fluid ounces, but I could or might do a recheck. The beans quantity I use is 1 tablespoon. Note also, I now use AeroPress for making the brew. The brew result is not weak.

Brew strength is subjective and all that matters is your own perception. But there are objective measures as well. There is a standard in the U.S. for coffee, one that is used to certify Gold Cup brewing devices. It specifies 55g of coffee per 1kg of water and a target strength of 1.15-1.55% total dissolved solids (link). The recipe you follow, even with the finest imaginable grind, would produce coffee a lot weaker than that standard. Are you sure it's really 1Tbls in 8-10oz?

 

[symbolipoint]

Brew strength is subjective and all that matters is your own perception. But there are objective measures as well. There is a standard in the U.S. for coffee, one that is used to certify Gold Cup brewing devices. It specifies 55g of coffee per 1kg of water and a target strength of 1.15-1.55% total dissolved solids (link). The recipe you follow, even with the finest imaginable grind, would produce coffee a lot weaker than that standard. Are you sure it's really 1Tbls in 8-10oz?

For my pour-over method used, yes; like that in bold in the quote.
AeroPress lets me obtain a strong brew (or, strong enough for my personal preference) if I use 1 teaspoon beans, grind them "fine", and add some 7 to 9 fluid ounces (I still need to recheck this) of HOT water. I have tended to use exclusively an AeroPress device for the last two years; because it's faster than pour-over method, and usually give me my prefered brew strength.

Of course personal 'subjectiveness' is part of this. I buy green, unroasted beans, and roast to a light roast, which seems to allow to fully avoid the medium/high roast with charcoal kind of flavor which most people probably like and expect.

I very much believe too, that grinding to fine (powdery is better than course) gives more extraction, making my own brewing stronger - more flavor. (I should also say something about brew-time, but maybe only later if someone is interested).

 

[JT Smith]

It's impossible to know what the strength of your coffee is without more information. But an educated guess can be made. A level tablespoon of coffee weighs 5-8g, depending mainly on the roast, lighter roasts being denser. So say you have an 8g dose. 8 US fluid ounces of hot water weighs 230g or so. That gives you a water-to-coffee ratio of 29 as compared to 18 in the standard I referenced above. A fine grind in an Aeropress could result in a relatively high extraction, say 25%. That would result in a strength of 0.09% as compared to the 1.15-1.55% range in the standard.

FWIW many, if not most, good cafes will serve coffee on the higher end of that strength range. Do you typically find that coffee in cafes is stronger than you prefer?

 

[symbolipoint]

It's impossible to know what the strength of your coffee is without more information. But an educated guess can be made. A level tablespoon of coffee weighs 5-8g, depending mainly on the roast, lighter roasts being denser. So say you have an 8g dose. 8 US fluid ounces of hot water weighs 230g or so. That gives you a water-to-coffee ratio of 29 as compared to 18 in the standard I referenced above. A fine grind in an Aeropress could result in a relatively high extraction, say 25%. That would result in a strength of 0.09% as compared to the 1.15-1.55% range in the standard.

FWIW many, if not most, good cafes will serve coffee on the higher end of that strength range. Do you typically find that coffee in cafes is stronger than you prefer?

I made a quick recheck on a brew using AeroPress this afternoon. It looks like 9 fluid ounces of water, and again my typical 1 tablespoon of beans, then ground finely. Flavor strength seems slightly dilute, but "good".

Restaurant coffees often taste about the same strength, but seem either moderate/medium roast or dark roast. Mine is most often better. (and that is still a subjective thing.)

 

[symbolipoint]

@JT Smith
A check on the weight of beans for this morning's brew, not using an accurate scale, shows about 3 grams of coffee beans (appears slighly less than 1 tablespoon); and then used about 9 fluid ounces HOT water. While flavor is not too strong, it is excellent.

add: Roasting was done two days ago. Finely ground for this brewing.

 

[JT Smith]

That ratio will produce coffee that is very dilute by most people's standards, no matter how well it's extracted. It's probably something like 0.3% dissolved solids.

 

[symbolipoint]

That ratio will produce coffee that is very dilute by most people's standards, no matter how well it's extracted. It's probably something like 0.3% dissolved solids.

My current serving I commented on from this morning has become stronger as it cooled. This is typical.