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I 'know' that freshly ground coffee is the best there is (within the quality of the beans, that is).

The question is whether this is true. Freshly ground coffee smells great, but does that affect the flavor after brewing? How long do these volatile flavors or smells last before the coffee goes 'stale'.

Can anybody (experts) taste the difference between freshly ground and brewed or not so freshly ground coffee? If so, what differences can be observed?

Edit as per talon8's link:

  • Freshly ground: brighter acidity, richest flavor.
  • 9 hours: very similar to the freshly-ground coffee, although a bit mellower; less “bright” notes.
  • 24 hours: some of the fruity flavors have faded; a bit less flavor in general.
  • 7 days: duller, significantly less flavor overall.

To the people that notice the difference in taste, do you agree with these observations?

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The fresh smell is aroma that is leaving the coffee, that is a hint. Prepare that cup quickly before more can get away :D –  daramarak Sep 14 '11 at 9:16
    
@daramarak, very good point, but do these aromas get trapped by the scalding hot water? Can you actually taste them? –  BaffledCook Sep 14 '11 at 11:04
    
I do not know for certain. Most flavors are water soluble or oils, both of these will be extracted by hot water that is for sure. –  daramarak Sep 14 '11 at 11:19
    
@Baffled if you are interested in the chemical properties, I would refer you to another question on how to manually brew coffee. The answer has a bevy of info on both the how and the why different methods are preferred, including leeching of oils and the temperature of water (basically, too cold not enough oil, too hot too much protein resulting in bitterness) –  mfg Sep 15 '11 at 18:02
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5 Answers

up vote 6 down vote accepted

Posted as answer by request of @BaffledCook:

Here's an slightly informal blog post outlining changes in taste between varying degrees of freshness in the grind of a coffee.

http://investigationsblog.wordpress.com/2010/03/03/do-i-really-have-to-grind-coffee-right-before-brewing-it/

The short version is that the coffee starts losing freshness as soon as it is ROASTED. The longer it sits the faster it goes stale. The more surface area it has (ie: you've ground it up; also, the finer the grind), the faster it goes stale. The more you expose it to air, the faster it goes stale. So, seal your coffee in an air tight container at room temperature. And grind as close to the time you add water to it as possible.

How much of a difference detected depends on the the actual coffee been, the roast, the taster's taste buds. If you buy a bean that's been sitting on the shelf for 3 months already, you will probably notice less of a difference than a bean that was roasted last week. I buy beans that are roasted and sold within a week, and I DO notice a difference if I leave the grounds for a day or two before drinking.

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Making good on my threat, I've accepted the answer. –  BaffledCook Sep 13 '11 at 17:22
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+1 For my espresso machine i through out grounds that are more than an hour old. Old grounds have less oils and less aroma, and I won't risk my coffee. –  daramarak Sep 14 '11 at 9:13
    
For me, that informal blog post was not quite on target. I think it significantly underestimates the effects of delay in using the ground coffee. The major problem here is that they used 15 day old coffee beans. I roast my own beans to use for drip coffee, and it normally reaches a flavor peak at 3-4 days. The coffee has much less flavor after 8 days, and WAY less after 15 days. –  Rick G Sep 17 '11 at 2:05
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Coffee begins to lose its flavour and freshness as soon as the roasting procedure is complete. Whole beans are best used within a month of roasting. The best way at looking at ground coffee is that it is similar to the whole bean, only with a whole lot more (pardon the poor english) surface area. That means that any of the breakdown that occurs to the bean will occur exponentially faster with a grind. You should always grind beans for each use, if you wish to have maximum flavour. I am no expert, but I can tell the difference between freshly ground beans (like my wife and I do), or not so freshly ground (like my in-laws do). I am no scientist, but the older the grind, the 'flatter' the flavour. It is definitely noticeable.

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Ah, in-laws and their crappy coffee. Mine drink weakly-brewed, store-bought Maxwell House. I think we can both agree that waking up to a bland cuppa' joe just makes visiting all the more... interesting. –  BobMcGee Sep 13 '11 at 14:07
    
My in-laws also microwave last night's leftover java. –  mrwienerdog Sep 13 '11 at 17:02
    
If you roast up some beans and cup samples everyday after roasting, you'll find that the coffee tastes best ('peaks') a few days after roasting. Some may take as long as a week. –  Megasaur Oct 7 '11 at 21:24
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I commonly drink espresso, french press, and stove-top (Moka-pot) coffee. Here's my personal experience:

Freshness

There are (at least) three different stages during which to measure freshness, and the length of time before the coffee goes stale changes at each stage.

Green Coffee

After the coffee cherry has been processed, but before roasting. Coffee in this stage will last months.

Roasted Whole Bean

There is some contention about how long coffee in this stage can be considered fresh, so your mileage may vary. I find that roasted beans last 1-2 weeks. I notice the change in flavor starting at about 1 week after roasting, and I'm ready to throw out old beans after 2 weeks.

Ground Coffee

Freshness lasts minutes (at best). Espresso will demonstrate this the most dramatically, but other coffee drinks will benefit from grinding immediately before brewing.

Flavor Differences

Flavor differences will depend on the specific coffee and the brew method, but in general fresh coffee is rich and tastes more like dark chocolate, while stale coffee is bland and tastes more like dirt. In my experience the ability to distinguish is learned, and it's hard to unlearn.

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I don't think coffee goes stale very quickly if stored in an airtight container. The beans are very dry, there is not much to go off

Some people like the aroma of freshly roasted coffee, some people just like it fresh ground. Some people just like coffee made from grounds in a French press

This is all personal and a subjective thing. There is certainly a difference between fresh ground and stored ground, but ground coffee does not go off

To me fresh roasted and fresh ground is great. But once it's an old roast, fresh or old ground makes little difference as far as I can taste in a cup of coffee

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I agree with the subjective part, but I don't agree at all with the idea that there is no difference. There certainly is a difference between freshly ground and stored ground. Just because you can't taste it, does not mean it doesn't change. investigationsblog.wordpress.com/2010/03/03/… –  talon8 Sep 13 '11 at 14:44
    
@talon8, put the link in an answer and I'll accept it as the article explains the flavor differences which is what the question is about. –  BaffledCook Sep 13 '11 at 15:50
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@BaffledCOok - seems upon a reread that the question is about whether fresh ground coffee is best "I 'know' that freshly ground coffee is the best there is (within the quality of the beans, that is). The question is whether this is true". You ask a few other questions as well, it is hard to tell that you were actually asking for the flavor differences between fresh and store. –  mrwienerdog Sep 13 '11 at 17:06
    
@mrwienerdog, true, maybe I should (have) post(ed) a number of questions. My goal was to establish whether the difference can be tasted and if so, what kind of differences can be noticed. The 'true' part was meant to refer to that. –  BaffledCook Sep 13 '11 at 17:16
    
Ah. Sorry my answer was not more specific vis a vis the answer you were searching for. –  mrwienerdog Sep 13 '11 at 18:41
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Yes, there are noticeable differences with storage, as others have noted. The coffee after roasting is pretty sterile and too dry to support microbiological growth, and the flavour changes are linked with chemical reactions with oxygen in the air. These are basically loss of flavour at first becoming flat and dull, followed by development of off flavours, becoming rancid and unpleasant, and may be less obvious with milked coffee. Roasted coffee beans are protected from oxygen by carbon dioxide evolved during roasting and probably last some weeks if transferred rapidly to an airtight container. After grinding the carbon dioxide is quickly released and the coffee is more vulnerable to oxidation - a good taster can detect flavour differences within hours. If the ground coffee is protected from oxygen, by vac-packing, valved packaging or flushing with an inert gas in air-tight packaging, it will still last some weeks, but deteriorate once the pack is opened. At any stage after roasting they benefit from protection from light and preferably storage in the fridge or even frozen. How soon all these changes are detectable or unacceptable, depends on many factors, especially the sensitivity of the taster - I've known people who happily drink coffee that makes me almost sick.

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