Chlorine Dioxide Works!!

Here are the results:

I used some American ale yeast that had been confirmed infected with Pediococcus for the test.

The control sample remained infected and tested positive in the aerobic and anaerobic tests.

The phosphoric acid killed some bacteria in the aerobic test, but not all. No bacteria was detected during the anaerobic test.

I treated the yeast with chlorine dioxide tabs I bought from dicks sporting goods. They cost $12 for 20 tablets. The brand is called portable Aqua. The first time I treated 200 ml of yeast slurry with one tablet. It failed both aerobic and anaerobic tests. So, I figured, I have all these tablets, let's see if more tablets work. I used 3 tablets and brought it back to the lab. The yeast PASSED both aerobic and anaerobic tests!! No bacteria and no effect on viability.

I used the yeast to make an American red ale. Normally I see activity within 12 hours of pitching. It took a little longer with this yeast. Activity started at 18 hours. Took a gravity sample after 6 days and took a taste. It was extremely clean and tasted great! I fermented the beer at the lower end of the temp range... 62 degrees.

I think these results are encouraging. For a small price, infected yeast can be salvaged. I think the sweet spot with this is 2 tablets per 200ml of slurry.

Let me know what you think of these results.

Can you talk a bit more about the tests you used to establish that the culture was no longer infected and how you measured yeast viability after chlorine dioxide treatment?

A nice control would have been a side-by-side ferment of wort with the original "infected yeast" sample to show that the pedio was indeed there, viable and able to infect beer wort. Otherwise it is a "if a tree falls in the woods, does anyone hear it?" scenario.

I suspect that very few yeast cultures remain free of contaminating organisms after leaving the production facility (if fact it would be naive to think so, considering we open these samples outside of a sterile atmosphere). The fact that homebrewers can continue to use such cultures indicate that although present, such contaminators are a non-issue.

The samples were plated with 6 Petri dishes of beer agar. An additive was used to stop any yeast growth, as to only allow bacteria to grow on the agar. 3 samples were placed in a temp controlled incubator and the other 3 placed in an Oxygen free environment.

Viability was tested by our lab before and after the phosphoric acid and chlorine dioxide were added.

I agree that once your yeast vial is open, contamination is inevitable. Yeast is one hell of an organism and I think it beats out anything else once fermentation starts. However, the chlorine dioxide completely cleans the yeast, thus giving the cleanest flavor possible.

I wonder if this could be used to stop an infection in the fermenter if you add the chlorine dioxide to the fermenter as soon as an infection was evident. Now THAT would be cool.

defrandj1 said:

The samples were plated with 6 Petri dishes of beer agar. An additive was used to stop any yeast growth, as to only allow bacteria to grow on the agar. 3 samples were placed in a temp controlled incubator and the other 3 placed in an Oxygen free environment.

Viability was tested by our lab before and after the phosphoric acid and chlorine dioxide were added.

I agree that once your yeast vial is open, contamination is inevitable. Yeast is one hell of an organism and I think it beats out anything else once fermentation starts. However, the chlorine dioxide completely cleans the yeast, thus giving the cleanest flavor possible.

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In your plating, did you also run a non-infected yeast sample to look at how many pedio colonies popped up there, as well as a plate that did not have any culture streaked onto it?

I also assume you repeated the plating experiment after the chlorine dioxide treatment?

You may also consider longer term culture experiments to see if the pedio pops back with time in culture. PCR tests would also establish that peddio is really gone.

...and are you going to share this data with the group?

BlueHouseBrewhaus said:

I wonder if this could be used to stop an infection in the fermenter if you add the chlorine dioxide to the fermenter as soon as an infection was evident. Now THAT would be cool.

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My concern would be residual chloride byproducts in the beer after treatment. If this happened, then treating for an infection would not be feasible.

Additionally, my experience with infections are that once they are established they are almost impossible to remove....which is why I'm asking so many probing questions of the OP

I like reading about new technology, and this is interesting.
But I'd rather toss infected yeast, and pay $8 to replace it, than risk the cost of my brew kit, plus hours of my time brewing/cleaning and more time bottling.

If this product was 90% effective at curing infected yeast, I still wouldn't use it.
If I had a batch of infected beer, I'd dump it, and probably junk the plastic bucket and other plastic equipment.


Here is a brewery focused presentation

http://www.mbaa.com/districts/Ontar...ng with chlorine dioxide jan 2014 aG_GAv3.pdf


Rather than washing infected yeast, when you make a starter, make it bigger, and save some in a jar for the next time.

ArcLight said:

Rather than washing infected yeast, when you make a starter, make it bigger, and save some in a jar for the next time.

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Good tip, I'll be doing that from now on. I hate infected yeast!