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Brews & Views Bulletin Board Service * Brews and Views Archive 2004 * February 18, 2004 * Acetic acid bacteria contamination treshold for flavour treshold? < Previous Next >

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Fredrik (213.114.44.219)
Posted on Sunday, February 08, 2004 - 11:49 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Does anyone have any information on the contamination treshold in cells/ml of acetobacter, before or after fermentation that is typically required to reach the flavour treshold of acetic acid in beer? (175 ppm)

The question is, how likely it is that I would spot an acetobacter in the microscope examining a beer that is possibly infected?

As compared to the yeasties, what ratio should I expect? 1:1000, 1:million ?

Any info would be appreciated.

/Fredrik
 

Brandon Dachel (216.177.117.110)
Posted on Sunday, February 08, 2004 - 01:32 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I don't know the direct answer to that question but if you're concerned about a acetobacter contamination just give it a week :)

The smell and appearance is absolutely unmistakable.
 

Mike Mayer (68.69.210.28)
Posted on Sunday, February 08, 2004 - 01:44 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Maybe I'm thinking about things too simply here, but unless there is a "cure" for infected beer, why worry about it?
 

Belly Buster Bob (142.177.104.222)
Posted on Sunday, February 08, 2004 - 01:55 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

the answer is "4"
 

Fredrik (213.114.44.219)
Posted on Sunday, February 08, 2004 - 02:46 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

The reason for my question is that I want to be sure the cidery flavour, which according the the sugar brew thread may be due to glucose induced acetic acid. I certainly do not think I have an infection, but I want to rule the possibility out befor jumping into conclusions.

I've examined my sugar brew in the microscope and found no rod shaped cells, so the question was, even if it was infected, how likely would I be to spot them?

1) The cidery flavour doesn't increase. It's been constant the last week.

2) There is no surfacefilm on the beer

It's not cidery enough to be vinegary though. But this may be a matter of levels. If you dilute vineager enough it will get cidery.

If I do not have an infection, I think the proposed explanation for the cidery flavour seems quite likely to may be the case.

I'll see how my current brew turns out. It's an all malt brew this time. And I'm using the same fermentor bucket, same desinfection procedure, all is the same.

If these there proves to be an infection after all there is only one think I can think of, and that is my microphone to the bubble logger. For obvious reasons it's not very easy to desinfect a microphone :) But even if that were the case? would the suckers really get down through the airlock? I find it unlikely. Moreover I am using 100% hennesy cognac in my airlock. Shouldn't that kill them?

/Fredrik
 

Beertracker (68.13.253.7)
Posted on Sunday, February 08, 2004 - 03:10 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

My trusted Siebel Institute of Technology 'Off-Flavors' handbook says it's only 50-70PPM for acetic acid. CHEERS! Beertracker
 

Bill Pierce (24.141.129.137)
Posted on Sunday, February 08, 2004 - 03:42 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Beertracker's information about the taste threshold for acetic acid agrees with mine. Fredrik, one way to identify infection experimentally is to take a sample (I know; this is not what some may be thinking here) of both the wort (without any yeast) and finished beer in a jar and set it aside covered with plastic film at room temperature. Observe and taste the samples at intervals of several days. Over time you will notice and be able to detect the effects of both wort-spoiling and beer-spoiling bacteria.
 

Fredrik (213.114.44.219)
Posted on Sunday, February 08, 2004 - 03:59 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I'm not going to argue about the treshold becauae I have not measured it myself. Siebel data is probably more correct. I just found a couple of non-authorative source who stated that the treshold for acetic acid in tap water is 33 ppm, and 175 ppm in "beer" (whatever that is). So I figure the treshold probably varies depending on the amount of other flavours in the beer in question. A dark flavourable beers may probably hide more than a light clean lager?

Hmm thanks Bill. Sounds like a good idea. I'll put a bottle at room temp and monitor the pH. I actually saved two PETs. One which I will store untouched for some months, and I will monitor the pH on the other one.

Thanks for all the responses!

/Fredrik
 

Chris Colby (66.25.196.39)
Posted on Sunday, February 08, 2004 - 10:32 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Fredrik,
You can search for bacteria under a microscope, but it's tedious. Once you get to a magnification under which you can discriminate yeast from bacteria, there aren't very many organisms in your viewfinder. Smaller commercial breweries screen for bacteria using differential media, often a growth media treated with actidione (cyclohexamide) to inhibit yeast growth. (Lewis and Young discuss this in their text, "Brewing: Second edition" (2002, Kluwer Academic/Plenum Publishers).


Chris Colby
Bastrop, TX

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