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Old 10-31-2009, 02:13 PM   #41
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BTW, the reason you get oxygen into the wort in a starter on a stirplate is due to gas diffusion. There is a direct path between the wort and the outside air and since there is also a concentration gradient between the interior or the flask and the exterior air, oxygen will enter the flask. If anyone really wants to understand how this works, research Fick's Law of Diffusion.

In a fermenter with an airlock, there's no way for oxygen, or any other gas, to enter the headspace once the fermenter is closed, except for the rare case where the gas in the fermenter is much warmer than the ambient temp and the contraction of the gas as it cools sucks exterior air backwards through the airlock.

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Old 10-31-2009, 03:36 PM   #42
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Actually THREE times, I also discussed Larmarguy's experiment and offer some ideas as to that as well.[/QUOTE]

True you did. I'm not saying we should stir our beer. You know where i am coming from.

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Old 10-31-2009, 03:39 PM   #43
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so what does "wet cardboard" taste like? and don't use the object in the definition. i know what paper tastes like, but im not about to imbibe cardboard to analize the flavor profile.

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Old 10-31-2009, 03:55 PM   #44
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Originally Posted by mordantly View Post
so what does "wet cardboard" taste like? and don't use the object in the definition. i know what paper tastes like, but im not about to imbibe cardboard to analize the flavor profile.
Most of those taste descriptors actually comes from the memory of what a taste or smell invokes rather than an actually flavor. The same thing goes for the "bandaid" one often mentioned, or the "wet horseblanket" mentioned in wine. It may not be logical and it may not be the actual smell or taste if you did suck on wet cardboard, but some of them are "archetype" and a lot of people can inherently understand.

It may stem from the "supertaster" gene found in some people, like how if some folks try to eat something with cilantro it tastes like soap in their mouth. Or those folks who understand the concept of "Umami" in food, which some say is the fifth taste, and other's say it doesn't exist. That's why some of these may be universal....buried in some bizarre genetic code in our brain...it's really fascinating.

But a lot people have no problem understanding the taste or concept of wet cardboard with thinking about it or tasting a beer with it in there, they may not have ever tasted wet cardboard...but their brain tends to "know" what it is like.....Or would taste like if they actually did.

To people in their 40's if you say "wallpaper paste" it invokes the memory of a certain kind of paste glue that many of us used in elementary school (which I don't know if it still exists in the era of gluesticks and such)...But many kids know what it smells like, as well as may have actually injested it.

At the same time, others may have the same chemical traits on a mollecular level like the smell/taste in invokes...like, iirc Acetaldehyde which we percieve as "green apples" is actually the chemical that gives green apples their distinctive taste...If I recall correctly.

THis is actually a great podcast about taste.....except this guy devoted his life to actually tasting wet carboard, horseblanket, dirt, long before he made his carreer as a wine critic;

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Basic Brewing Radio
Gary Vaynerchuk of Wine Library TV brings the thunder to BBR and gives us his perspectives on the art of tasting as he samples homebrew.

Click to listen, Mp-3
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Old 10-31-2009, 04:08 PM   #45
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The only beers I have had that smelled like this are porters. not good!

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Old 10-31-2009, 04:32 PM   #46
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Revvy, the link doesn't work. can you try again?

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Old 10-31-2009, 04:41 PM   #47
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I make a considerable amount of wine at home each year and one of the things I do to my wines is to gently shake the carboy to release trapped CO2 from the wine to aide in clearing. I also use a vacuum pump to remove the trapped CO2. Also, the wine is typically racked off the yeast and sediment prior to any significant amount of shaking to de-gas.

I can understand the OP questioning why this practice is not done with beer and I also see the point of keeping O2 exposure to a minimum. In all, It is an interesting thread.

Oh..... I take no stand either way here, cause I have a long way to go before I can offer up any significant input as it relates to Home Brewed Beer.

Salute!

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Old 10-31-2009, 06:26 PM   #48
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Quote:
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so what does "wet cardboard" taste like? and don't use the object in the definition. i know what paper tastes like, but im not about to imbibe cardboard to analize the flavor profile.
Wet cardboard and wet paper taste similar. I think you'll know it when you taste it. It also tastes just like it smells.

Alternately, buy a beer, take the cap off, recap it, shake it up a bunch and leave it as hot as possible (preferably around 100 F or more) for about a week and then chill it and drink it.

Note that trans-2-nonenal tastes like paper or cardboard but there are other products of oxidation in beer that taste like other things (and are desirable in some beers).
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Old 11-01-2009, 12:52 AM   #49
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Revvy, the link doesn't work. can you try again?
I fixed it!!! reclick the linky.
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Old 11-01-2009, 01:10 PM   #50
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My understanding is that "oxidation flavors" are caused by excess dissolved o2. From this it would seem prudent to drive off excess dissolved oxygen as quickly as possible, prehaps through agitation in an oxygen defficient environment.
Your statement shows a lack of understanding of the brewing process.



Oxidation flavors are indeed caused by excess dissolved oxygen. However, the prime source for oxidation off-flavors hasn't anything to do with fermentation. It has to do with the mash.

There is a phenomenon called hot side aeration which sets up the precursors for in-package staling and development of off-flavors that evoke wet cardboard or paper. Hot side aeration (HSA) is caused when sweet wort pics up too much oxygen, usually through excessive agitation.

Before you go all wobbly about HSA affecting your beer, though, take my advice and stop worrying about it. HSA is of concern to large beer factories, where they're pumping wort at hundreds of gallons per minute. In order to induce HSA-derived flavor precursors in your wort, you'd have to pump it through a garden hose at a high rate of speed and shoot it into your kettle.

That said, you can pick up off-flavors from air post-ferment, but it's not from the introduction of oxygen. It's through the introduction of non-S. cerevisae microorganisms - in other words, contamination. The same flavors associated with HSA can also come from contamination.

I mean to say, how many production breweries still use open fermentation? If ever there was a situation where green-beer oxidation would be virtually guaranteed, it's then. It doesn't happen, because it happens on the other end of the brewhouse. Contamination is also unlikely, provided an open ferment is conducted properly, because infecting microorganisms cannot withstand the environment of high krauesen.

Agitation can be beneficial, however. Yeast strains which are excessively flocculent - Ringwood springs to mind - often need to be roused periodically during the ferment, in order to maintain contact with the wort. Whether it's twice-daily stirring with a sanitized implement or constant agitation with a sanitized submersible pump - I've done both - extremely flocculent strains sometimes need the physical assist. I have to note I've never experienced staling precursors developing with those methods.

It is good to keep beer away from air after bitter-wort aeration and the onset of the ferment. But it's for different reasons than the development of flavor precursors of oxidation. The moral of the story is "stop worrying about it".

Oh, and about de-gassing: Vintners de-gas their product because it's intended to be still; I for one don't like fizzy Sauvignon, and I'm sure you don't either. Brewers intend their product to be quick (carbonated); a good conditioning regime will take into consideration the amount of dissolved CO2 in the green beer before conditioning and add a proportionate amount of priming solution to reach a targeted volume. Thus de-gassing is a waste of time.

Plus it adds to global warming.

Have fun,

Bob
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Last edited by Bob; 11-01-2009 at 01:14 PM.
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