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Thread: To Acid Wash or Not to

  1. #1
    Join Date
    Oct 2002

    To Acid Wash or Not to

    We are considering implementing an acid wash program.

    I’m interested to learn if other micos are using an acid wash to clean yeast between batches. If so, are you doing it between every batch or periodically? I understand that some people don’t recommend the practice at all. Please let me know your feelings one way or the other. Finally, It is my understanding that an acid wash will not prevent a problem from occurring, but may stop an already present contamination from spreading to the next batch. Do you agree?


    Steve Aichele
    From: Steve Aichele (

  2. #2
    Join Date
    Oct 2002
    I cannot definitely answer about micros using acid washing, but I believe some are.

    Acid washing if carried out correctly will remove the majority of bacterial
    contamination. If you are suffering from wild yeast infection, then I'm
    afraid the only answer is to get a new batch of contamition free yeast in.

    Acid washing is NOT a substitute for good hygiene, but complements it. It
    was introduced to help reduce the ATNC (nitroso compounds)levels in beers that are believed to be carcinogenic.

    The yeast needs to be healthy to start with. If it is poor due to old age or lack of nutrients then correct acid washing may kill off a large amount of yeast.

    The yeast must be slurried, and kept below 4 degrees C, ideally between 2 and 4 deg C, and stirred continously whilst it is being washed. If you cannot arrange permanent stirring (because you are doing it by hand), then it must be stirred whilst adding the acid to the yeast slurry, and regularly after that. The acid wash stand should be 1 to 4 hours, a good working target would be 2 hours, before pitching into well aerated wort.

    Target pH 2.1, range 2.0 to 2.2 using food grade orthophosphoric acid. If
    the temperature is well controlled, then a slightly lower pH is not reputed to do much harm, but this will vary between yeast strains.

    If the yeast is kept cold and stirred I have heard of instances of good yeast surviving for 24 hour before pitching, so a small extension should not cause a serious problem.

    I do not advise acid washing more than one brews worth at a time, in spite of this comment.

    Hope this helps

    From: Dick Murton

  3. #3
    Join Date
    Jun 2003

    acid washed yeast

    NO, NO, NO, do not get into the mind set of acid washing yeast to solve your greater problems.

    It is a road to ruin.
    I believe acid washing yeast is only and should only be used in a last resort ....mabe to save a special strain?...mabe because you have no more options .....but IF you have two more options , go with no washing ,and clean a little harder , ferment a little cooler/ slower, .or change strains..?.....
    You will spend a fortune on yeast ,and waste time and effort,,,,,,
    ....try one more time.....

  4. #4
    Join Date
    Oct 2002
    Chesterfield, UK
    Whoa there. I totally agree that acid washing will not improve fermentation performance. Even if carried out very well it will at best not make it worse, but carried out badly will make fermetnations / yeast far worse.

    Acid washing was introduced to help reduce the number af bacteria in pitching yeast and thus fermetning wort in order to reduce the amount of nitrosamines in the final beer. In the UK, this is limited to no more than 30 ppbillion. I expect similar statutory levels apply in the States & Canada.

    As such it can only be successfully applied to healthy yeast. It will not differentiate between yeast strains. It is one of the most effective methods of controlling wort bacteria. The big problem is you can look down a microscope and the yeast looks to be bacteria free, but unfortunately due to the differential focusing, and size difference of many bacteria to yeast, it is easy to miss the bacteria.

    I do agree though that the first line of defence is good hygiene and regular yeast replacement with fresh bacteria free cultures.


  5. #5
    Join Date
    Jan 2003
    I agree with Dick's comments. Acid washing is an important tool and I don't believe it should be limited to a last resort. I worked in a 60 bbl brewery where we washed 1056 EVERY PITCH and never had any problem due to slow fermentations. As a matter of fact we had our beer take a silver medal at WBC. Our hygeine was impeccable and acid washing was one more step we used to produce zero bacteria counts all the way through packaging. I also know of breweries which use chlorine dioxide (brand name Oxine) to wash their yeast with excellent results. Not every yeast enjoys the acid bath, but many do. I would not hesitate to use a proper acid washing routine on every batch. Just make sure you are consistent with time/temperature/pH, and monitor your fermentations carefully. Something you would do anyway. Good luck.

  6. #6
    Join Date
    Jun 2003
    At my brewery we washed yeast prior to each pitching in chlorine dioxide (Dioxychlor from Birko) solution. You need to acidify the water used (less than one gallon) to a pH of 3.0 with phosphoric acid and then add 2 ml of Dioxychlor for each gallon of yeast slurry. If the solution turns a pale yellow color it has been successfully activated and you can pour it into your slurry and mix well. This should be done an hour before pitching, but can be done even earlier in the day. The beauty of chlorine dioxide is that it does not harm the yeast if left sitting in contact too long. Therefore, if the unexpected happens (power outage, broken gas line, etc.) your yeast will not die on you if you have to wait to brew again another day. Birko literature claims that yeast washed with Dioxychlor can be left for three days with no ill effects, but they do suggest that after three days contact time that the slurry be fed with fresh wort prior to pitching. It worked for me, so I would suggest you give it a try.
    Ron Downer

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