Why coffee needs to ''rest'' before making espresso - Page 2

Discuss flavors, brew temperatures, blending, and cupping notes.
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barry

Postby barry » Mar 12, 2006, 1:35 pm

King Seven wrote:What about the possibility that not all staling reactions produce a negative effect?

I know most staling reactions are bad - but surely some of the chemistry going on in the rest phase makes it taste better?



this is a qualitative factor, correct?

what tastes "better"? if you prefer the taste of slightly staled coffee, that's fine. some people prefer the taste of seriously staled coffee.


the reality is, of course, that very few people ever taste really fresh coffee when buying retail, and rarely do shops pull espresso from really fresh coffee. the blends and roasts, therefore, are evaluated not on their freshest characteristics, but on how they taste after they've had some time to degas. if a blend/roast is developed with an anticipated use date beyond the first day or two, then it seems to me that the taste when very fresh will not be what is expected, and therefore folks will feel the blend tastes "better" two or three days out. that is the reality of the roasting business.

if a coffee is going to be used within a day or two of roasting, the blend & roast should be developed accordingly, to balance out the acidy characteristic. such a blend would likely taste flat after several days "resting".


so, to sum up: "resting" is staling; there's really no way of getting around that. blends may taste "better" after several days resting because that is their target taste and target use. coffee can be blended/roasted for immediate use, and such blends would likely not taste the same (or even favorable) after resting. it all comes down to working with the coffee towards a target use & taste.

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espressoperson

Postby espressoperson » Mar 12, 2006, 1:41 pm

barry wrote:i really have to laugh sometimes when folks talk about home roasting to get fresh coffee, and then letting it sit for 3 to 5 days before using it. really.


I'm not sure if you're making your argument based on your actual experience or based on some principle. If you can enjoy espresso on day one, more power to you, your coffee, and your taste buds.

I roast coffee regularly so I can enjoy it when I think it tastes best. My favorite blend is Sweet Maria's Monkey Espresso Blend I roast to full city, sometimes to plus or almost Vienna. On day one the espresso is yuck. On day two it is OK. On day three it is good to very good. On day four it is heaven! It reminds me why I drink espresso and makes it worth all the time and trouble I go through to reach that peak. Days five through the time it takes to finish a half pound batch (to about day 10) is a slow fade of that peak experience.

I don't care about the principles involved - staling, resting, maturing, degassing, whatever. Tasting is believing.
michaelb, lmwdp 24

Bob Barraza

Postby Bob Barraza » Mar 13, 2006, 11:37 am

Well, just back from a side trip without access to cyber space, so a little late jumping in. However, staling, aging, maturing, etc. is an interesting subject from the point of view of the chemist. There are many foods such as cheeses and wines that benefit enormously from a careful aging. My thought is that most of these processes are the result of slow oxidation and/or hydrolysis. Benign chemical changes that impact differently with time on the palate.

When it comes to taste, I don't think that anyone would argue that it is subjective, and often associated with some custom or tradition. For example, the 'ideal coffee' varies wildly from country to country. My conclusion is that a lot of it is simply what you are accustomed too.

I am convinced that the C02 content in the coffee is the key that makes espresso brewed coffee unique to any other brewing process. The reason is that brewing under temperature and pressure allows the C02 to dissolve in the brewing water. As Dan noted in the first note, the dissolved carbon dioxide forms carbonic acids which in turn lowers the pH of the brewing water.

I have often read that coffee is made up of more than 1000 compounds that can be extracted from the roasted beans. I imagine that carefully prepared 'cowboy coffee' would get most of these compounds out for a cup of full bodied coffee that might lead to the Brokeback Syndrome, but I digress. On the other extreme, I have often read that in espresso coffee, we usually will only extract about half of the extractibles from the beans. Which of these compounds and the relative amounts is carefully controlled by us with brew temperature, volume, time, etc.

Back to the lab. Most chemical analysis, and even some commercial purification of compounds, is done by chromatography, which usually involves a stationary phase (the coffee grounds) and a mobile phase (brewing water). As the mobile phase passes over the stationary phase, compounds will dissolve in the mobile phase and be carried off with the mobile phase. As the mobile phase picks up compounds, its ability to further dissolve other compounds is mitigated until some kind of equilibrium is reached.

Too much information? Perhaps, but once you can 'visualize' this process you can begin to see how things can change with the amount of C02 present. For example, all solubilities are pH dependent. Therefore, as you modify the temperature and/or pH of the brewing water, you will modify which of the available compounds will preferentially extract. Depending on which flavors you prefer, you will find a 'peak performance' for you based on days from roasting.

Since our discussion with Dan last Friday, I have thought of one other probable factor associated with the C02 content. You can imagine that the chromatography process that I mentioned is occurring at the interface between solid and liquid. Therefore, the polarity of the mobile phase will greatly impact the extraction profile. Difficult to do in text format, but if you consider that water, H20 actually looks somewhat like this: H-O-H. Then consider CO2 which would look more like: O-C-O, which in turn forms carbonic acid, etc. Therefore, beyond the effect of pH, the amount of CO2 dissolved will further impact the extraction profile.

I'm afraid there is still more..... Since the coffee grounds are porous, the mobile phase must 'wet' or penetrate into the bean matrix to complete the extraction. The fresher the coffee, the higher the content of CO2 which is already trying to boil off a room temperature. Well, hit it with water at around 190 deg. F and you can imagine how violent the outgassing is. This is bound to be a one way process which delays the wetting phase. Since we are only extracting for about 25 seconds, this is significant enough to also change the extraction profile.

Conclusion: if everyone is paying a premium for aged cheese and wine, why are we paying a premium for fresh coffee?
Bob Barraza

LMWDP#0021

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barry

Postby barry » Mar 13, 2006, 11:42 pm

Bob Barraza wrote:When it comes to taste, I don't think that anyone would argue that it is subjective, and often associated with some custom or tradition. For example, the 'ideal coffee' varies wildly from country to country. My conclusion is that a lot of it is simply what you are accustomed too.


a quick taste of "rioy" coffee will confirm that. UGH!


The fresher the coffee, the higher the content of CO2 which is already trying to boil off a room temperature. Well, hit it with water at around 190 deg. F and you can imagine how violent the outgassing is. This is bound to be a one way process which delays the wetting phase. Since we are only extracting for about 25 seconds, this is significant enough to also change the extraction profile.


but this has to work against the brew pressure, right?



time to start selling "pre-rested" coffee for a premium!

King Seven

Postby King Seven » Mar 14, 2006, 5:45 am

How do we decide when staling begins?
What exactly is staling? Are we talking loss of volatiles? Oxidation reactions?

Do you use your coffee ground straight from the cooling tray? One hour later? One day?
The problem I have with absolutely fresh coffee (air cooled here, rather than quenched - which is another freshness debate right there) is that I often get a smoke characteristic in the cup, regardless of how I brew. This goes quite quickly (within a day usually) and to me the coffee is improved by it.

We know from the extraction process that there is a great deal in coffee, even the "best coffee in the world" that is undesirable. Of course that is subjective, but espresso has its guidelines built on subjectivity.

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barry

Postby barry » Mar 14, 2006, 11:56 am

King Seven wrote:How do we decide when staling begins?
What exactly is staling? Are we talking loss of volatiles? Oxidation reactions?



staling begins the moment roasting stops.

it is composed of three major phases: loss of aromatics; oxidative reactions; and non-oxidative reactions.

Grant

Postby Grant » Mar 14, 2006, 12:42 pm

As a beer/wine/scotch lover, I find this thread quite interesting. In some ways (with no real concious thought about it), I have always thought of bean roasting in terms relative to the aging of scotch and wine...but after reading Barry's comments (not that I agree with them necessarily), I think bean roasting is maybe MORE relative to the aging process of beer instead (though I like the cheese comments as well). Beer goes from an immature (IMO - like fresh roasted beans) unready to drink state, to a state where it is considered "good" or "best" for consumption after a period of time (staling?), to a point where it begins to break down and lose desireable taste qualities...all within a sealed system with a chemical process going on.

While "technically" you could call it staling in the initial stages, I am sure food chemists, brewers, distillers, bakers, etc. would all not agree on that term in the initial stages as their relative products are "resting" or "maturing" or "seasoning" to become consumable.

Grant

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barry

Postby barry » Mar 14, 2006, 11:36 pm

Grant wrote:Beer goes from an immature (IMO - like fresh roasted beans) unready to drink state, to a state where it is considered "good" or "best" for consumption after a period of time (staling?), to a point where it begins to break down and lose desireable taste qualities...all within a sealed system with a chemical process going on.

While "technically" you could call it staling in the initial stages, I am sure food chemists, brewers, distillers, bakers, etc. would all not agree on that term in the initial stages as their relative products are "resting" or "maturing" or "seasoning" to become consumable.


if it weren't for the loss of aromatics, i'd be less inclined to think of "resting" as "staling". the CO2 production helps delay the onset of oxidative staling and the non-oxidative processes really don't do a whole lot in the initial days. but the aromatic losses which happen along with the evolution of CO2... well... an yrg on day 3 is a shadow of fresh yrg. same with kenya. same with many other coffees. i like coffee from the moment it is roasted until the moment i don't. right now, i'm using 2 month old coffee at home. it's still moderately tasty, but with a slight cardboard component, and still better than most espresso i could buy in cafes in the area.

--barry "gotta use it up soon."

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rasqual

Postby rasqual » Mar 20, 2006, 2:01 am

Bob Barraza wrote:I'm afraid there is still more..... Since the coffee grounds are porous, the mobile phase must 'wet' or penetrate into the bean matrix to complete the extraction. The fresher the coffee, the higher the content of CO2 which is already trying to boil off a room temperature. Well, hit it with water at around 190 deg. F and you can imagine how violent the outgassing is. This is bound to be a one way process which delays the wetting phase. Since we are only extracting for about 25 seconds, this is significant enough to also change the extraction profile.

I've read that quenching during roast cooling also adds moisture content to the beans, putatively with a more consistent grind as a consequence (I'd think this relates to the outer part of the bean). I'm wondering whether this might have an effect on wetting efficiency during this fulmination. On the other hand, I wonder what a slightly less dry outer layer of the bean has on its outgassing prior to grinding.

I've started quenching in part for fun, in part for cooling efficiency, and in part out of superstition in this regard.

roblumba

Postby roblumba » Mar 23, 2006, 2:34 pm

Staling is such a negative word, loaded with negative connotations. If the coffee flavor peaks on day 4, then it has aged to its peak.

Case in point, I bought some Ecco Caffe Northern Italian Espresso. It was okay the first few days. I wasn't impressed. But several days into it, it tasted amazing, especially in the lattes. My vanilla syrups lattes had a very smooth milk chocolatey taste.

So my feedback to Ecco Caffe, "You Northern Italian roast ages very nicely."

We never see wine or liquor advertised as "staled 10 years". Same with coffee, it can have a beneficial aging period.