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Author Topic: Sanitizer Comparison  (Read 12703 times)

Offline charles1968

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Re: Sanitizer Comparison
« Reply #15 on: November 08, 2015, 01:27:20 pm »
Eric streaked the plate before before he applied the sanitizer.

And dried it.

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Re: Sanitizer Comparison
« Reply #16 on: November 08, 2015, 02:08:45 pm »
Eric streaked the plate before before he applied the sanitizer.

Yes, but then Eric immediately applied sanitizer.  That's not a valid test.   The low pH of the Star San solution prevented the culture from multiplying.  It did not necessary kill the yeast culture.  The real test is to streak the plate, incubate the culture until visible colony-forming units appear, overlay the colony with sanitizer, wait until the santiizer's stated killing period has elasped, and then test for viability by restreaking another plate or staining yeast from the plate on a hemocytometer after diluting it with sterile water.   The ratio of dead cells to live cells is the only valid test for a sanitizer.

Offline mabrungard

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Re: Sanitizer Comparison
« Reply #17 on: November 08, 2015, 02:52:56 pm »
OK, Mark's approach makes sense. Eric, get going!  :)
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Offline troybinso

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Re: Sanitizer Comparison
« Reply #18 on: November 08, 2015, 02:59:05 pm »
Eric streaked the plate before before he applied the sanitizer.
The ratio of dead cells to live cells is the only valid test for a sanitizer.

While this may be true when you are only considering the definition of "sanitary", I don't think it really matters practically. If the star-san did the best job of getting rid of yeast and bacteria, I don't care if it killed the cells or just washed them away, as long as the undesirable microbes are gone.

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Re: Sanitizer Comparison
« Reply #19 on: November 08, 2015, 03:10:19 pm »
I agree, Eric streaked prior to sanitizer application and the test seems to represent a condition that may be similar to actual conditions.

However, the test does not simulate actual conditions.  The test was flawed the moment that the surface of the plate was allowed to remain at Star San pH during the incubation period.  That's not what happens when one sanitizes with Star San due to the pH buffering effect of adding a much larger volume of liquid with a higher pH to the Star San sanitized vessel. 

The other plates tested the sanitizer's ability to kill viable cells because the sanitizers have no residual effect.  Alcohol ceases to be effective the moment that it flashes off, and so does iodophor when the iodine sublimates into iodine gas.  Those two plates tested the sanitizers' ability to truly kill vegetative cells because nothing was left to hinder the growth of cells after the sanitizers left the surface as gases.

One of the terminology problems that we routinely see in home brewing is the intermixing of the terms sanitation and sterilization.  The goal of a sanitizer is not kill every vegetative cell.  The goal of a sanitizer is to kill most of the vegetative cells.  True sterilization kills 100% of the vegetative cells and 100% of the spores that can germinate into vegetative cells. Boiling is in between sanitizing and sterilizing in that it kills 100% of vegetative cells, but does not kill spores.

Let's look at a commercial sanitizer for one's home; namely, Lysol.  It's maker claims that Lysol kills 99.9% of viable cells.  It only takes one viable cell to produce a colony-forming unit (CFU), which is why CFUs are known as pure cultures.  That claim means that we are almost guaranteed to have one CFU form if the sample that we use to streak a plate contains at least 1,000 viable vegetative cells.   A  CFU contains a large number of cells.  A Saccharomyces cell is 5 to 10 µm in diameter, which means yeast cells are at least 1/5th of the smallest size that is visible to the naked eye.

While yeast cells will not replicate very well at Star San solution pH, it does not mean that they are dead.  A yeast culture can contain a bacteria load.  Yet, the bacteria load will not rear its ugly head as long as the pH remains below 4.6, which is the pH at which many bacteria species stop replicating (one of the reasons why we do not want to rinse yeast with and store it under boiled water is because doing so raises the pH of the culture).  Yeast is also susceptible to pH-based growth limiting.  It's just that domesticated brewer's yeast can withstand a lower pH than most bacteria species.   Anyone who has made a batch of mead where the pH dropped into the low threes has noticed sluggish to non-existent fermentation. The yeast cells are not dead.  All one needs to is to buffer the pH of the mead back up to over 3.5 or so, and the fermentation will usually restart.


I shot the photo shown below.  It is a batch of Star San that I made with water that contains 130ppm as CaCO3 alkalinity. Yet, the pH is way below the pH at which most brewer's yeast will replicate or even function, and the pH of Star San that is made with distilled water is even lower (< 2.0).




Offline HoosierBrew

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Re: Sanitizer Comparison
« Reply #20 on: November 08, 2015, 03:17:44 pm »
While this may be true when you are only considering the definition of "sanitary", I don't think it really matters practically. If the star-san did the best job of getting rid of yeast and bacteria, I don't care if it killed the cells or just washed them away, as long as the undesirable microbes are gone.

That's my feeling, too.
Jon H.

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Re: Sanitizer Comparison
« Reply #21 on: November 08, 2015, 03:22:44 pm »
While this may be true when you are only considering the definition of "sanitary", I don't think it really matters practically. If the star-san did the best job of getting rid of yeast and bacteria, I don't care if it killed the cells or just washed them away, as long as the undesirable microbes are gone.

I am contesting that the Star San did not kill the yeast cells.  The pH of the plate merely prevented the cells from replicating just as the pH of a yeast culture will keep most pH-sensitive bacteria loads from replicating, but the culture does not kill the load.  The bacteria load carried by a culture is really what limits the ability to repitch it.  Every repitching event is also a bacteria load amplification event because the pH of wort is above 4.6, there is little to no ethanol, and wort usually contains dissolved O2.  The yeast culture shuts down the replication of bacteria by hogging the O2 supply, lowering the pH of the wort from around 5.2 to under 4.6, and producing ethanol, which is toxic to all living organisms, including the culture itself.



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Re: Sanitizer Comparison
« Reply #22 on: November 08, 2015, 03:54:27 pm »
That's my feeling, too.

I wish that I would have photographed the Lin's Wild Yeast Medium plates that I streaked with samples taken from several batches in a row.  All tested positive for wild yeast. I was not certain that Star San was the culprit at that point.  However, after switching back to using bleach as my primary sanitizer and having an equal number of batches test negative for wild yeast infection, I was left with no choice, but to study sanitizers and their modes of action.  I was completely floored when I discovered that acid-anionic sanitizers do not kill yeast or mold. 

I have posted multiple references to published literature that state that acid-anionic sanitizers do not kill yeast or mold due to the fact that yeast and mold cells hold the wrong charge since bringing my experience and findings to the attention of the community.  When confronted with the truth at NHC, the owner of Five Star openly admitted that Star San does not kill yeast.  The owner basically said that Star San merely stuns yeast when confronted with the facts and asked for a conformation.  If you do not believe me, write Five Star armed with literature references that I have posted to this forum that state that acid-anionic sanitizers do not kill yeast or mold and watch the tap dance.

In closing, there are two types of Star San users.   Those who have encountered a wild yeast infection while using the product as their primary sanitizer, and those who will encounter a wild yeast infection while using Star San as their primary sanitizer.   It is just a matter of time.  I do not wish the problem that I experienced when using Star San on my worst enemy.  It took me a year to identify the source of the problem because I too blindly accepted the hype that surrounds Star San.   It was not until I realized that the off-flavor showed up around the same time that I switched from using bleach or iodophor to Star San that I started to take a hard look at the product.  Star San is not used in commercial breweries for a reason, and not just because Star San is incompatible with CIP equipment.

Offline charles1968

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Re: Sanitizer Comparison
« Reply #23 on: November 08, 2015, 03:57:01 pm »
Star San provided a vicious barrier between the media and the microflora during streaking, resulting in a much lower cell count transfer.
The Star San wasn't sprayed on before streaking.

Eric immediately applied sanitizer.  That's not a valid test.
The sanitizer was applied after ten minutes, not immediately.

The low pH of the Star San solution prevented the culture from multiplying.
A film of Star San was sprayed on and the liquid poured off after two minutes. The was very little residual Star San.

I can't help getting the impression that you decided the test was flawed without actually reading how it was conducted.

Offline charles1968

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Re: Sanitizer Comparison
« Reply #24 on: November 08, 2015, 04:05:28 pm »
A possible confounding factor is that there might have been chemical reactions between the sanitizer and the agar that affected how well the agar could support growth. So for that reason the result may not be 100% applicable to brewing.

Offline charles1968

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Re: Sanitizer Comparison
« Reply #25 on: November 08, 2015, 04:18:29 pm »
I have posted multiple references to published literature that state that acid-anionic sanitizers do not kill yeast or mold due to the fact that yeast and mold cells hold the wrong charge since bringing my experience and findings to the attention of the community.  When confronted with the truth at NHC, the owner of Five Star openly admitted that Star San does not kill yeast.

It's no secret. Lots of people use Star San/Saniclean for acid washing. It wouldn't work if the yeast were killed.

Offline charles1968

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Re: Sanitizer Comparison
« Reply #26 on: November 08, 2015, 04:23:26 pm »
That's my feeling, too.
In closing, there are two types of Star San users.   Those who have encountered a wild yeast infection while using the product as their primary sanitizer, and those who will encounter a wild yeast infection while using Star San as their primary sanitizer.   It is just a matter of time.

Wild yeast isn't such a problem as most brewers don't keep harvesting and repitching the same yeast. And for lager brewers it's even less of a problem thanks to the low temp.

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Re: Sanitizer Comparison
« Reply #27 on: November 08, 2015, 04:42:29 pm »
It's no secret. Lots of people use Star San/Saniclean for acid washing. It wouldn't work if the yeast were killed.

It makes sense that people are using Star San for acid washing yeast.  After all, the product is 50% phosphoric acid (Star San's MSDS: http://www.jstrack.org/brewing/msds/starsan.pdf), and food-grade phosphoric acid is often used for that task. A quick search of the web returned several posts were people have independently reached the same conclusion as I have about Star San (although their experiences do not appear to be as painful as mine).  There are even posts like the one linked below where people have in fact attempted to acid wash yeast with Star San.

http://www.homebrewchatter.com/board/showthread.php?t=19819

Offline charles1968

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Re: Sanitizer Comparison
« Reply #28 on: November 08, 2015, 04:49:10 pm »
I do it myself and have no problem brewing a healthy starter after washing - with bacterial load decimated. Obviously you can't acid wash wild yeast away, but if you wash lager yeast or a cold-toletant ale yeast like Nottingham or S05 then you can pitch cold and suppress wild yeast while getting numbers up.

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Re: Sanitizer Comparison
« Reply #29 on: November 08, 2015, 10:11:48 pm »
Wild yeast isn't such a problem as most brewers don't keep harvesting and repitching the same yeast. And for lager brewers it's even less of a problem thanks to the low temp.

That's true.  In my case, the problem was that the wild yeast infection was pervasive.   I start with much less yeast than most brewers.  I am pitching cells grown in 40ml of 5% autoclaved wort from a couple of inoculation loop scrapes from a slant.  The first-level starter is completely aseptic, but the second level starter is made with boiled wort and sanitized equipment.  Wild yeast has a chance to rear its ugly head when one is stepping 15:1 or 20:1 at that level.   The amount of yeast in a 40ml starter is tiny compared to the amount of yeast in a White Labs vial or Wyeast smack pack.  There's much less room for error in the process.