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Old 01-28-2010, 06:13 PM   #1
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Default Excessive Aging Good for Ales? Probably Not.

http://pubs.acs.org/doi/abs/10.1021/...rchHistoryKey=

The aging and consequent changes in flavor molecules of a top-fermented beer were studied. Different aging conditions were imposed on freshly bottled beer. After 6 months of aging, the concentration changes were recorded for acetate esters, ethyl esters, carbonyls, Maillard compounds, dioxolanes, and furanic ethers. For some flavor compounds, the changes with time of storage were monitored at different temperatures, either with CO2 or with air in the headspace of the bottles. For some molecules a relationship was determined between concentration changes and sensory evaluation results. A decrease in volatile esters was responsible for a reduced fruity flavor during aging. On the contrary, various carbonyl compounds, some ethyl esters, Maillard compounds, dioxolanes, and furanic ethers showed a marked increase, due to oxidative and nonoxidative reactions. A very high increase was found for furfural, 2-furanmethanol, and especially the furanic ether, 2-furfuryl ethyl ether (FEE). For FEE a flavor threshold in beer of 6 μg/L was determined. In the aged top-fermented beer, FEE concentrations multiple times the flavor threshold were observed. This was associated with the appearance of a typical solvent-like flavor. As the FEE concentration increased with time at an almost constant rate, with or without air in the headspace, FEE (and probably other furanic ethers) is proposed as a good candidate to evaluate the thermal stress imposed on beer.

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Old 01-28-2010, 09:14 PM   #2
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There's a difference between regular strength and high strength ale though. I don't think they made a distinction.
But it depends on your definition of good to. I have found a lot of massive stouts and barleywines to start to get a sherry type flavor after time - oxidization.

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Old 01-29-2010, 08:12 PM   #3
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Default Probably True!

Skip to the bottom for the tl;dr

As many people don't have access to ACS publication, I've taken the time to read through the article and summarize some interesting points. Despite the sensationalist title used in the OP and the copy/paste of the abstract, the manuscripts supports many accepted theories/practices that are employed by homebrewers regarding aging and depending on the style, could result in positive effects (ester reduction being a key example). Poor aging characteristics were seen for beer stored at 40C (104F in case you don't want to convert it).

To set the stage, the authors took a fresh batch of beligan ale (ABV=7.5%) put 250mL of beer in the bottle which left a headspace of 10 mL. The head space was filled with either C02 or Air and sealed. The authors don't specify whether beer is already carbonated, given the nature of the experiment, it seems reasonable to assume that they received freshly-bottle force carbonated beer. The beer was stored at 0C, 20C, and 40C and a large number of known flavor compounds were tested over a 6 month period. A tasting panel was used identify flavor characteristics of the beer after 6 months. The authors found that ONLY the beer stored at 40C had a radically different taste profile from a beer stored at 0C. Note this is a comparison of 6 months of aging at 0C vs. 6 months at 40C, there is no way to reproducibly compare the taste fresh beer to 6 months aged beer.

Quote:
Originally Posted by J. Agri. Food Chem. '03, 51, 6782
Two of the most important esters for beer flavor are isoamyl acetate, with a fruity banana flavor, and ethyl acetate, with a fruity solvent flavor (17). .... Consequently, ester hydrolysis during storage may be the main cause of the loss of the fruity estery flavor note of beer. In top fermented beers particularly, such loss of an initial strong estery flavor may also cause other components to dominate the flavor profile.
6 Months of aging, regardless of oxygen content or temperature, reduced the amount of fruity esters. Chemically, this is intuitive result given the susceptibility of esters to hydrolysis. Beer is of course mostly water and given enough time, most esters will hydrolyze. From a practical homebrewing perspective, this result supports the accepted theory/practice that aging will correct a strong fruity ester flavor component (e.q. fermented a bit to warm and your pale ale tastes like a banana).

Interestingly, the authors found that air in the headspace lead to increase in diacetyl formation over 6-months. But, the diacetyl concentrations never reached the flavor threshold.

Quote:
Originally Posted by J. Agri. Food Chem. '03, 51, 6782
As a general conclusion it becomes clear that in a top-fermented beer, all examined components, present in fresh beer, are not in chemical equilibrium conditions. During aging,
chemical and biochemical reactions initiate either a decrease (e.g., esters) or an increase (ethyl esters, carbonyl compounds, Maillard compounds, dioxolanes, and furanic ethers). Some reactions are intensified by the presence of air in the headspace.
To summarize their conclusion, fruity ester flavor components decrease with aging (hydrolysis of esters), color can dark at higher temperatures (40C, Maillard compounds), and a warming solvent-like taste develops from storage at 40C (furanic ethers). Looking carefully at the falvor thresholds for the furanic ether, the authors estimated 6-13 ug/ml being detectable. In 12 days of atorage at 40C the beer had developed 20 ug/mL of this flavor component which increased dramatically over the six month period. In contrast storage temperatures of 20C does not generate enough furanic ether to pass the flavor threshold until 119 days and even then the levels stay below 20 ug/mL after 6 months.

Quote:
Originally Posted by J. Agri. Food Chem. '03, 51, 6782
The concentration detected [for 2-furfuryl ethyl ether] during beer aging was much higher and could be related to the development of a solvent-like flavor.
The author's final statement is much more tempered than the jdc2's title has implied. The furanic ether (2-furfuryl ethyl ether = FFE) the authors discussed passes the flavor threshold by roughly a factor of two at reasonable storage temperatures (20C) after 6 months of aging. The language used to describe the flavor implies that it is a mild component. It is important to consider that the authors are using a belgian pale ale so this component could standout, in a bigger beer it probably wouldn't be noticeable.

At the end of the day, authors propose that FFE could be used as a marker for age and thermal stress on beer.


tl;dr
  • Aging changes the beer.
  • Esters are reduced
  • Air in the bottle headspace increases oxidation
  • Storing beer at 104F is bad
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Old 01-29-2010, 08:19 PM   #4
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troll.

i was first

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Old 01-29-2010, 08:27 PM   #5
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I don't think anyone is excessively aging lower gravity beer for a long time on purpose. Its a pretty well accepted fact that a little age on bigger beers helps. Too much age, and yes, flavors start to fade/mute, some oxidation occurs etc. And its pretty obvious you should never store beer at 40C (104F).

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Old 01-29-2010, 08:53 PM   #6
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Quote:
Originally Posted by motobrewer View Post
...
Can't this one be a productive thread?
There's real science up there and good science at that.
It won't revolutionize the world but it does quantify some things that we've all observed happening when aging beer.

Revvy's always harping on letting beer age to clean itself up, we all hand out anecdotal evidence that aging beer cleans up off flavors. Now there is an article to quote from a peer-review journal instead of just "brewer lore"

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Originally Posted by Edcculus View Post
And its pretty obvious you should never store beer at 40C (104F).
True, but living in SoCal without central air means that my storage closet is going to hit 100+ degrees for a few months. I was surprised to see how quickly some undesirable compounds would develop and how fast some others are destroyed. Looks like I've got storage issues to address before the summer.

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Old 01-29-2010, 09:04 PM   #7
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Quote:
Originally Posted by Rushis View Post
Can't this one be a productive thread?
There's real science up there and good science at that.
It won't revolutionize the world but it does quantify some things that we've all observed happening when aging beer.
And on top of that, it has nothing to do with his water report!
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Old 01-29-2010, 09:05 PM   #8
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lol, fair enough.

yuri's thread has pretty much proven empirically that smaller ales, when made properly, are great without excessive aging.

plus I made a porter 27 days ago that was great on wednesday. a tiny bit bready/harsh, but certainly good. i keg, however.

i find it very strange that this jdc character is constantly starting threads that go against theories that a lot of people here hold to be truths, be it thru testing or research. not to mention i don't think anyone here is advocating the need for aging 6 months, unless it's a very strong ale.

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Old 01-29-2010, 09:14 PM   #9
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Who stores beer at that temperature?

What were the differences found in the 20C beers?

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Old 01-29-2010, 09:20 PM   #10
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Loaded question. You have to define "excessive"......

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