Author Topic: Another Starter Question  (Read 2258 times)

Offline klickitat jim

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Re: Another Starter Question
« Reply #30 on: April 18, 2014, 06:54:25 AM »
My random guess would be nonenol, and produces a stale cardboard aroma and flavor at high enough concentration

Offline Steve in TX

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Re: Another Starter Question
« Reply #31 on: April 18, 2014, 08:05:56 AM »
...stale cardboard aroma and flavor

Personally, I like my cardboard fresh.   :P

Offline klickitat jim

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Re: Another Starter Question
« Reply #32 on: April 18, 2014, 08:46:36 AM »
Me too but I'm curious if I'm right. If I am that's rather scary

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Re: Another Starter Question
« Reply #33 on: April 18, 2014, 10:17:30 AM »
So now I'm curious and I suspect you might know. When yeast metabolize ethanol in the presence of oxygen, what do they produce and does it affect flavor?

Acetaldehyde, and then acetic acid if they continue to oxidize the acetaldehyde. I'd imagine how much of each depends on the oxygen available, and probably on the strain as well.
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Offline S. cerevisiae

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Re: Another Starter Question
« Reply #34 on: April 18, 2014, 11:05:32 AM »
So now I'm curious and I suspect you might know. When yeast metabolize ethanol in the presence of oxygen, what do they produce and does it affect flavor?

Yeast cells basically reverse the acetaldehyde to ethanol process. 

The following reduction occurs:

Ethanol -> Acetaldehyde -> Acetate -> Acetyl-CoA

Acetyl-CoA is used as an energy source via the Krebs Cycle (a.k.a. the TCA Cycle).  As with glycolysis, incomplete utilization of ethanol as a carbon source can result in acetaldehyde and/or ester production.

Mark V.

Just say "no" to yeast rinsing
https://www.homebrewersassociation.org/forum/index.php?topic=19850.msg252492#msg252492

A pale ale losing points for being too pale is like a vicar being defrocked for being too godly. It is no wonder that beer judges get such a bad rap.  - Graham Wheeler

Offline narcout

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Re: Another Starter Question
« Reply #35 on: April 18, 2014, 01:29:54 PM »
Many poor practices are preached in amateur brewing like they are gospel (e.g., rinsing yeast with boiled tap water).

I don't reuse yeast very often, but when I do I follow the procedure outlined in Yeast.

Is there a bettter method I should investigate?


Offline narcout

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Re: Another Starter Question
« Reply #36 on: April 18, 2014, 06:25:53 PM »
Like so many things, we are working with sub optimal equipment, knowledge, and facilities in the homebrew world

Commercial brewing is the bastardization of homebrewing, not the other way around.  I really feel that they are the ones in the sub-optimal position.

Online HoosierBrew

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Re: Another Starter Question
« Reply #37 on: April 18, 2014, 07:32:47 PM »
Like so many things, we are working with sub optimal equipment, knowledge, and facilities in the homebrew world

Commercial brewing is the bastardization of homebrewing, not the other way around.  I really feel that they are the ones in the sub-optimal position.

^^THIS^^

I appreciate and absorb every oz of info that I can get my hands on from commercial brewing.  Then I filter it to determine if it's something I can use at home, in some fashion. Sometimes yes, sometimes no. But I don't feel I've failed as a brewer if I can't. It just didn't work for me.
Jon H.

Offline klickitat jim

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Re: Another Starter Question
« Reply #38 on: April 18, 2014, 07:50:14 PM »
Like so many things, we are working with sub optimal equipment, knowledge, and facilities in the homebrew world

Commercial brewing is the bastardization of homebrewing, not the other way around.  I really feel that they are the ones in the sub-optimal position.
To rephrase something Forest Gump said, maybe both is true at the same time. I love what both said. I wonder what homebrewers said to the first guy who sold a beer.

Offline morticaixavier

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Re: Another Starter Question
« Reply #39 on: April 18, 2014, 08:19:35 PM »
Like so many things, we are working with sub optimal equipment, knowledge, and facilities in the homebrew world

Commercial brewing is the bastardization of homebrewing, not the other way around.  I really feel that they are the ones in the sub-optimal position.
To rephrase something Forest Gump said, maybe both is true at the same time. I love what both said. I wonder what homebrewers said to the first guy who sold a beer.

it was probably a gal rather than a guy.
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Offline klickitat jim

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Re: Another Starter Question
« Reply #40 on: April 18, 2014, 09:07:52 PM »
Good point

Offline S. cerevisiae

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Re: Another Starter Question
« Reply #41 on: April 19, 2014, 07:22:46 AM »
Commercial brewing is the bastardization of homebrewing, not the other way around.  I really feel that they are the ones in the sub-optimal position.

Prey tell?   
Mark V.

Just say "no" to yeast rinsing
https://www.homebrewersassociation.org/forum/index.php?topic=19850.msg252492#msg252492

A pale ale losing points for being too pale is like a vicar being defrocked for being too godly. It is no wonder that beer judges get such a bad rap.  - Graham Wheeler

Offline alestateyall

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Re: Another Starter Question
« Reply #42 on: April 19, 2014, 09:13:55 AM »

Commercial brewing is the bastardization of homebrewing, not the other way around.  I really feel that they are the ones in the sub-optimal position.

Prey tell?

Is that a pun intentionally indicating you are waiting to strike or did you mean "pray" tell? ;)
Tommy M.
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Offline S. cerevisiae

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Re: Another Starter Question
« Reply #43 on: April 19, 2014, 09:37:45 AM »
I don't reuse yeast very often, but when I do I follow the procedure outlined in Yeast.

Is there a bettter method I should investigate?

The best way to crop is to "top crop" at high krausen.  However, top-cropping requires one to use a true top-cropping strain.   Top-cropping naturally purifies a culture because wild yeast and bacteria do not floc to the top.  Top-cropped yeast can be repitched almost indefinitely.

When using a non-top-cropping yeast strain, I usually leave enough liquid behind after racking to be able to swirl the solids back into suspension (my primary volume is 1/3 to 1/2  gallon larger than the volume  I expect to rack).  Swirling the solids back into solution using green beer, waiting a few minutes for the heaviest fraction to settle, and then decanting the liquid fraction has the same effect as rinsing with boiled water; however, it keeps the low pH, ethanol laden environment intact.   If one wants to attempt to rid the culture of mutants, one can perform a second decant as soon as a creamy layer of yeast forms in the first decant. 

One of the first things that a yeast culture does when pitched into a batch of wort is to lower the pH from around 5.2 to around 4.1.  One has heard that pathogens do not grow in beer.  One of the reasons why pathogens do not grow in beer is due to its relatively low pH.  Clostridium botulin growth is inhibited below pH 4.6. 

Contrary to what was written in early amateur brewing books such as Brewing Lager Beer, brewing yeast cultures do not respire in wort due to a phenomenon known as the Crabtree effect.  Hence, brewing yeasts do not go through a period of resparitive (aerobic) growth before they start to reproduce fermentatively (anaerobic growth).  In the presence of glucose levels above the Crabtree threshold, all reproduction is fermentative.  As you probably noticed while reading Yeast, yeast cultures use dissolved oxygen to  build ergosterol and unsaturated fatty acid (UFA) reserves (these reserves are shared with with all of the daughter cells).  Yeast perform this feat by shunting oxygen to the respirative (aerobic) metabolic pathway while simultaneously metabolizing the carbon source via the fermentative (anaerobic) metabolic pathway.

What this preference to reproduce fermentatively means to a brewer is that yeast cells pretty much start producing ethanol as soon as they are pitched into a batch of wort.  While ethanol has a limiting effect on the viability of a yeast culture, it also protects the culture from infection.  Boiled water is not truly sterile.  Boiled tap water also tends to have a pH of at least 7.0; therefore, it raises the pH of the culture.

With the above said, most experienced amateur brewers eventually reach the conclusion that one can just crop and repitch without doing anything to separate the viable cells from the dead cells and break material, especially if they leave most of the break and hop material in the kettle.   Less is definitely more when cropping yeast.
« Last Edit: April 19, 2014, 10:41:31 AM by S. cerevisiae »
Mark V.

Just say "no" to yeast rinsing
https://www.homebrewersassociation.org/forum/index.php?topic=19850.msg252492#msg252492

A pale ale losing points for being too pale is like a vicar being defrocked for being too godly. It is no wonder that beer judges get such a bad rap.  - Graham Wheeler

Offline S. cerevisiae

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Re: Another Starter Question
« Reply #44 on: April 19, 2014, 09:44:05 AM »
Is that a pun intentionally indicating you are waiting to strike or did you mean "pray" tell? ;)

Yes, it was a pun. 
Mark V.

Just say "no" to yeast rinsing
https://www.homebrewersassociation.org/forum/index.php?topic=19850.msg252492#msg252492

A pale ale losing points for being too pale is like a vicar being defrocked for being too godly. It is no wonder that beer judges get such a bad rap.  - Graham Wheeler