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Old 12-18-2012, 02:53 PM   #1
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Default Contamination in process

Recently, after brewing a hefeweizen I detected tartness in the final product and began wondering if I had contamination in my brewing process. Consequently, I decided to try a “forced wort test” described in Chris White’s book on yeast during my next brew day. What I did was sterilized a couple of canning jars in a pressure cooker for 20 minutes and put a sample of fresh wort, but before adding yeast, in the jars. After about 36 hours, I am detecting what appears to be the beginning of fermentation on the top of the samples. The questions I have are what others think about what might be happening and how one determines what is fermenting?

thanks

Jim

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Old 12-18-2012, 05:13 PM   #2
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You detected a tartness in the final product meaning this beer was was packaged, carbonated and conditioned, refrigerated and poured?

In addition, what yeast did you use for this hefeweizen and at what temperature did you ferment it. What was the OG/FG.

Also, where did this "fresh wort" you speak of come from. As for the final question asked: What is fermenting is the sugar from whatever malt you used but you did not tell us

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Old 12-18-2012, 07:19 PM   #3
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Thank you for your feedback and questions. The hefeweizen was packaged and carbonated. I first noticed the tartness during fermentation, but the tartness subsided over time. I used WLP320 at 65 degrees fermentation. OG of 1.052 FG was 1.011.

The fermentation test I speak of is a fresh brew. Obviously it is sugar that is fermenting, but what I did was collect a sample of the wort before adding a yeast starter, and put the sample in a sterilized jar as a means of measuring contamination in my process. After 36 hours this non-inoculated sample is fermenting.

Have others attempting a similar test of their process and if so, to what result?

Jim

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Old 12-18-2012, 08:35 PM   #4
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Quote:
Originally Posted by jaw94087
Thank you for your feedback and questions. The hefeweizen was packaged and carbonated. I first noticed the tartness during fermentation, but the tartness subsided over time. I used WLP320 at 65 degrees fermentation. OG of 1.052 FG was 1.011.

The fermentation test I speak of is a fresh brew. Obviously it is sugar that is fermenting, but what I did was collect a sample of the wort before adding a yeast starter, and put the sample in a sterilized jar as a means of measuring contamination in my process. After 36 hours this non-inoculated sample is fermenting.

Have others attempting a similar test of their process and if so, to what result?

Jim
Most likely the "tartness" you tasted was just "green", young beer that was just not quite ready and if it subsided and mellowed it simply properly conditioned.

As for your test, no I have never tried this although it is considered to be a forced fermentation test to verify the ferment ability of the wort and attenuation of the yeast and is a considered scientific approach in brewing.

As to discovery of potential contamination I'm not so sure it's relevant to the process. Just because you experience no contamination in a small same does not directly correlate to the possibility of infection in primary, secondary or bottle/keg as the number of potential variables increase at each step in the process and the various equipment used in each.
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Old 12-18-2012, 10:04 PM   #5
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Duboman,

Yes, there is the forced fermentation test to determine potential fermentation. However, the forced wort test is different. It helps show contamination in the cold side, and while contamination can occur after sampling, a positive contamination indication does indicate something going on. So it is certainly relevant. I am interested if others have tried it, and how to determine the kind of contamination.see:

http://www.homebrewtalk.com/f128/force-test-wort-158974/

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Old 12-18-2012, 10:27 PM   #6
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Quote:
Originally Posted by jaw94087
Duboman,

Yes, there is the forced fermentation test to determine potential fermentation. However, the forced wort test is different. It helps show contamination in the cold side, and while contamination can occur after sampling, a positive contamination indication does indicate something going on. So it is certainly relevant. I am interested if others have tried it, and how to determine the kind of contamination.see:

http://www.homebrewtalk.com/f128/force-test-wort-158974/
Thanks for the thread link, a couple years old and not very conclusive.

I get what you are trying to do and can see how it might be a worthwhile experiment but I still feel as though its really not going to result in much.

There is always the possibility of contamination throughout the brewing process which is why cleaning and sanitizing as best practice is paramount. In addition, fermentation and the creation of alcohol inhibits most benign contamination factors. IMO I really don't think this type of test would preclude one from actually getting an infection if somewhere down the process something is missed.

After all you are only taking a small wort sample, in all honesty if you keep the remaining wort sitting around until this test is done you may have introduced other contaminants in the remaining wort that went undiscovered.

That being said, it's interesting and I'm curious to see what other folks may have to say......
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Old 03-26-2013, 07:39 PM   #7
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I'm doing the forced wort test on my last batch. My motivation is plain old curiosity. How clean is my process?? I drew off a sample of wort into a sanitized container before pitching my yeast. If something grows quickly in the sample then that is an indication of contamination either in my brew day process or the container or both.

I'm 36 hours into the experiment and I've got the wort on a heat pad.

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Old 03-27-2013, 06:06 AM   #8
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I do a force wort test with every batch as a QA measure. Most samples will never turn up anything but every now and then something starts to grow after 2 or 3 days. It usually appears like wild yeast, but can't be sure. Then I'll go about cleaning things up a bit. It helps keep me honest.

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Old 03-27-2013, 01:09 PM   #9
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I have always seen this called the George Fix test. I've done it a few times. 72 hours+ is considered the goal. If you are seeing activity at 36 hours, there is something up.

Give us some details about your process and we might can point at a few things. I could start pulling stuff out of the air, but it would be a waste of time without knowing more about your process.

Step through your process from 20 minutes before the end of boil and let's see what we get. Be detailed. Do you cover while chilling, what kind of chiller, do you whirlpool, how are you aerating, what sanitizers are you using, do you fear the foam and rinse, is your silicone tubing 10 years old, etc etc etc.

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Old 03-27-2013, 01:18 PM   #10
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Quote:
Originally Posted by jaw94087 View Post
how one determines what is fermenting?
I forgot about that question. You would inoculate a sterile plate and place it in an incubator for a couple days. Once the colonies grow up, you then have a series of tests to determine what the growth is.

Some of the tests:
Visual colony inspection
Microscopic inspection
Gram Stain
Carbohydrate Fermentation
Hydrogen Sulfide
Urease
Catalase
Oxidase
Nitrate Reduction

Ands some other stuff. Basically, you don't! You could plate it up and decide if it is yeast or something else fairly easily. Since you have a pressure cooker, you could make a sterile plate if you buy some agar.

The LS6610 from White Labs (http://www.whitelabs.com/files/AnalyticalLabServices_0.pdf) would identify what is in it. But that's $144, so unless you REALLY want to know it's kinda pricey!
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