I was wondering if you might comment on your opinion of acid washing versus using a chlorine dioxide (CLO2) wash. It seems that the use of CLO2 might be a bit easier and quicker than an acid wash based on [very limited] reading related to this subject.

-Is this something that might be relevant to a homebrewer?
-If you think this is a viable option, do you have any practical hints and/or suggestions on this method of washing yeast.

FWIW, below are some links to relevant articles:

http://www.birkocorp.com/brewing/yeast.asp
http://www.brewingscience.com/yeast_care.htm

Regards,
Chris Thomas

RESPONSE:

To be honest we do not have much experience with yeast washing using Chlorine Dioxide. The data from the web link you sent look impressive. However Chlorine Dioxide is a general biocide which "attacks" all kind of microorganisms including yeast. The trick is that you need to have a certain concentration that kills bacteria but does not harm the yeast. The effective concentration range is relatively narrow.

One of the critical parameters to control the concentration of Chlorine Dioxide in the yeast cream is the effectiveness of mixing. If the mixing is not properly done you have too high concentration of Chlorine Dioxide in some parts of your yeast cream which kills the yeast and you will have parts where the concentration is too low and therefore not effective. In small vessels with a good mixing apparatus it might work well but in larger yeast storage vessels you probably end up with problems.

Another parameter is the cell concentration; depending on the cell concentration you have to adjust the concentration of your Chlorine Dioxide to be effective.

We know of a large industrial brewery that successfully tried this procedure in the lab but did not implement it in their production because it was too difficult to control.

So for home brewing applications this method probably works but you have to be careful to look after your parameters like mixing, cell concentration....

Regards,
Forbes & Tobias