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  • Peracetic acid

    Hi all,

    I have a bucket of Purisan peracetic acid. The label says it is 5.25% peroxyacetic acid, 22% hydrogen peroxide, and 72.75% inert ingredients.

    I wanted to make sure that what is generally advised is 100ppm of peroxyacetic acid, NOT 100ppm of peroxyacetic acid AND hydrogen peroxide.

    Put it this way: Given my product's ingredients as outlined above, for my calculations, do I assume that I'm working with a 5.25% solution (or 52,500 ppm) to be diluted down to 100ppm, or is it a 27.25% solution (of peroxyacetic acid and hydrogen peroxide) that needs to be diluted down to 100ppm?

    Other questions:

    1) how dangerous is this stuff, after it's been diluted? Should eye protection and gloves be worn after it is diluted as well?

    2) is 100pm sufficient for sanitizing a bright tank?

    3) if the product is not rinsed afterward, is there not a threat of oxidizarion, and vinegar taints? I'm making cider, so I'm worried about both possibilities.

    Thanks all!!

    Mike

  • #2
    First-off, contact your sales rep. that person can tell you everything you need to know about dilution rates for that product. Second, get some test strips, these will tell you if your mix is still good, or is needing replacement. It will also tell you if your dilution is correct.

    As for the residues, they break down into non flavor active compounds pretty quickly. Never had any issues, even with our lightest beers. As long as you don't leave gallons of the stuff in there, you should be fine.

    Comment


    • #3
      Firstly - Jebzter is spot on - the supplier is always the first point of contact for any detailed advice such as this on chemicals - for CIP, water treatment etc.

      PAA is widely used in the cider industry in the UK at least, and presumably elsewhere around the world. The only problem is if you do not drain out tanks fully before putting cider in the tank - but that comment also applies to beer, soft drinks etc. I know one major cider producer that refuses to have PAA on site, but having surveyed their CIP systems, the control systems were old and very basic - i.e. not really up to modern best practices, so poor that leaving puddles of cider in the tanks would have been quite easy, and they accept that this was the source of the problem, not residues left as a very thin film on the tank surfaces. You will also be best off rinsing out the PAA in lines with fresh sterile water (there's a problem doing that in many production sites I accept), to eliminate contact in the lines.

      Re safety - I have always worked on 150 to 250 ppm PAA to achieve kill rate in sensible times. And no, I wouldn't drink it or want to rinse my eyes out with the stuff, but no problems dilute on hands, unlike the concentrate - actually it got rid a couple of small warts after a couple of weeks of regular dipping into soak baths - but really, hooks and then handle any fittings with gloves should be the order of the day.
      dick

      Comment


      • #4
        I agree with Jeb and Dick, however I usually skip the rep and go straight to the manufacturer whenever possible.

        My Divosan Activ VT5 has very detailed parameters for proper usage. (5.1% PAA, 21.7% H2O2). It also has directions for food items, porous surface, disinfection, ect depending on your industry. PAA is used in a lot of food facilities.

        It recommends on hard non-porous food contacting surfaces to use a minimum of 1.0-1.7oz per 5 gallons producing 87.7-149ppm PAA, and 373-635ppm of H2O2. If using water below 5*C (40*F) then you should use the highest end of this concentration. If protecting against Listeria Monocytogenes, then you should use a minimum of 1.2oz/5 gallons (105ppm PAA, 448ppm H2O2)

        At these concentrations you only need a contact time of 1 minute. As a rule of practice, I always cycle a minimum of 10 mins. My typical concentrations are around 120-150ppm of actual PAA. I like the PAA strips for a quick test, although the ones I have seen usually max out at the 120ppm mark. Enough to know I am safe, but I have to rely on my measurements for accuracy on the ppm.

        At 250ppm you've got some potent stuff and I would hold my nose! I'm not sure what the permissible exposure limit is, but that's enough to wear out your senses for a few days, lol. I always recommend gloves, and safety glasses are best practices with any chemicals. I used to work where the joke was, "you wash your hands before you go to the restroom" so these are common place for me.

        I like the PAA specifically for its no rinse properties, and no stains like Iodine based. As said above, as long as you drain it, you won't have any issues. It breaks down to organic compounds basically.

        Comment


        • #5
          And get some test strips to confirm concentration - cheep and easy.
          Brewmaster, Minocqua Brewing Company
          tbriggs@minocquabrewingcompany.com
          "Your results may vary"

          Comment


          • #6
            Originally posted by Ted Briggs View Post
            And get some test strips to confirm concentration - cheep and easy.
            Yep. My chem supplier gave me test kits for each of the products I use. Once I dialed in my concentrations, I put together a spreadsheet with each chemical used, dilution rate, CIP time, and application temperature. Every once in a while, I check each one to make sure nothing has changed. So far, it's been a pretty reliable way to get consistent results easily.

            Cheers,
            --
            Don

            Comment


            • #7
              PAA effectiveness can be very temperature dependent. Breaks down rapidly particularly in dilute form if warm, and doesn't break down if cold such as in cold rooms, so the kill time is vastly longer than 10 minutes.

              Having said the above - there was a recent discussion on use in soak baths where people had tested thir SBs and weren't getting anything like the rate of breakdown in warm conditions that a couple of breweries I worked at experienced - even when left without any kit being soaked - for trials on chemical breakdown rates.
              dick

              Comment


              • #8
                Originally posted by dick murton View Post
                PAA effectiveness can be very temperature dependent. Breaks down rapidly particularly in dilute form if warm, and doesn't break down if cold such as in cold rooms, so the kill time is vastly longer than 10 minutes.

                Having said the above - there was a recent discussion on use in soak baths where people had tested thir SBs and weren't getting anything like the rate of breakdown in warm conditions that a couple of breweries I worked at experienced - even when left without any kit being soaked - for trials on chemical breakdown rates.
                I have heard that temperature makes a difference as well, and previous manufacturer instructions of other brands have recommended to stay below 30*C (86*F) in dilution water, but I have never actually seen the data myself. I stay under that anyways as safe practice. I also avoid excessive sunlight, as I have heard (but not seen data) that it catalyses breakdown as well.

                My understanding is that PAA itself will in fact breakdown significantly (up to 84%) somewhat quickly (as little as one day), but in conjunction with CH3COOH (acetic), H2O2 (hydrogen peroxide), H2O, and H2SO4 (sulfuric) the breakdown will take up to a few months. The solutions we use are likely combinations with similar effects, as I have routinely measure significant quantities of PAA after more than 7 days. Perhaps similar to the results you mention. I still replace every 4-6 days in practice, and check daily or more.

                A very good source of information on sterilization methods is Disinfection, Sterilization, and Preservation - Seymour S. Block. It details Iodine, PAA, and numerous other processes.

                I think that we still will achieve sufficient sanitation at one minute contact time (or a practical 10) so long as the concentration is 100ppm of PAA (and appropriate ppm of H2O2) or more by the time the cycle is completed. I have plated samples from sanitized vessels in the past and never had any signs of growth.

                I will certainly concede that sterilization or disinfection standards would require a much longer contact time (generally between 20-50 minutes depending on the organisms) with a PAA solution, but my standards are sanitation and not sterilization or disinfection.

                In a practical sense, our tanks are very likely clean and free of organisms prior to sanitation anyhow if a proper detergent cycle and rinse is run. A caustic solution will kill most living organisms prior, and a good rinse will wash the majority away. The sanitation step, again in a practical sense, is just a secondary protection against organisms and chemical residues. A simple test to this is to plate a swab from a tank that has been only cleaned and incubate it. I have not seen growth on these type of plates in my practical experience, but I have only done it a handful of times.

                Comment


                • #9
                  These are the figures I was given a few years ago, for complete kill of Sacc Cerevisiae.

                  So based on the fact that many brewery contaminating bacteria require the same number of PUs, although not exactly the same, I assume that kill times with PAA for common brewery bacteria would be similar - probably a wild assumption, but.... Although I was given no figures, or if I was I have long since lost them, I seem to remember being told by yet another chemical supplier when first introducing PAA - so a good few years ago, that most "brewery bacteria" were killed at similar rates with PAA as yeast

                  Time (mins) Temp oC Conc PAA
                  15 17 200
                  15 4 900

                  I was told by a different supplier today at a CIP training session, that they work on 10 minutes contact time at 200 ppm PAA at these temperatures.

                  Cheers
                  dick

                  Comment


                  • #10
                    Sorry about the spacing - I had it sorted, but when posted, it removed all the spaces
                    dick

                    Comment


                    • #11
                      I have to go look it up again, but brewers yeast is one of the hardest for PAA to kill. Bacteria and some other yeasts are killed very quickly with PAA at concentrations down to 100ppm. I need to go find it, it was a study for food processing. But PAA is the best next to steam to deal with brewery sanitation, and it deals with it in 10 minutes or less.

                      Comment


                      • #12
                        I can not find a whole lot of information specifically on S. Cerevisiae, but as little as 9ppm of PAA over a three hour period will produce a total kill of Bacillus subtilis, Byssochlamys fulva, and Aspergillus niger, and below 100ppm is effective in less than 5 mins on L. monocytogenes, S. aureus, and E. faecium. Candida albicans is again reduced to acceptable levels in three hours at 5ppm None of these are organisms are considered particularly easy to kill as far as I know. Higher concentrations will not always conclude faster kill times, but in most circumstances it will.

                        White papers from Heritage Systems Inc says "PAA at 75 mg / L is reported to successfully kill 100% of a 107 cell / ml yeast or bacterial population in 30 seconds." They are dealing primarily with wine, which may be S. boulardii (they don't specify) however that species is believed to have derived from S. cerevisiae and I personally would suspect it has similar characteristics when it comes to resistance of PAA. http://www.heritagesystemsinc.com/Do...AA-Lancer5.pdf

                        Here is a link to Perasan (the actual product in question) with the info on some of the species listed about in an under five minute span. http://envirotech.com/wp-content/upl...Sanitation.pdf

                        Here is a link to a UC Davis report that at least references the studies suggesting temps up to 34*C and pH up to 8.5 are acceptable for PAA and that, again, yeast, bacterial and algae are reduced to acceptable levels.


                        I myself have not seen any particular manufacturer recommending levels of PAA up to 200ppm for brewery uses, but it very well could be the case. For direct food contact, limits are around 85ppm I believe. We are not exactly having direct food contact, and dilution will occur in our circumstances so that is certainly a factor.

                        I am always open to learning and if either of you have data regarding S cerevisiae vs PAA or others I would definitely be interested in looking at it. For now this data has been the most complete I can find, and has been plenty sufficient in me trusting the 100ppm to 180ppm concentrations.

                        In any event, lab plating and testing is what I consider to be my definitive conclusion for proper dosage rates. I prefer not to use much more than is necessary to complete an effective sanitization, and plating and incubation give me full confidence that at 100ppm or more at 10 mins or longer is plenty sufficient to reach effective sanitization. Again not reaching for sterilization, or I would run a three hour cycle at a slightly higher ppm.

                        I would totally agree with steam being one of the best possible options, when it is practical, and based on the above I would definitely feel comfortable with the methods mentioned by Dick. I am just suggesting they are above what is necessary for good results. I have had many people tell me things but I am usually convinced only by data, in house or otherwise.

                        Comment


                        • #13
                          [QUOTE=jebzter;215409]First-off, contact your sales rep. that person can tell you everything you need to know about dilution rates for that product. Second, get some test strips, these will tell you if your mix is still good, or is needing replacement. It will also tell you if your dilution is correct.

                          As for the residues, they break down into non flavor active compounds pretty quickly. Never had any issues, even with our lightest beers. As long as you don't leave gallons of the stuff in there, you should be fine

                          Thanks for the help!! Mike

                          Comment


                          • #14
                            Here is that file I found on PAA.



                            It shows that temperature, not concentration is the biggest factor in kill time for many things even at two different concentration levels.

                            Comment


                            • #15
                              Originally posted by jebzter View Post
                              Here is that file I found on PAA.



                              It shows that temperature, not concentration is the biggest factor in kill time for many things even at two different concentration levels.
                              Thanks for supplying that. I have book marked it as it is very useful information. I wish it had a little more info on the source of the study, but am certainly willing to take it on its face value.

                              It seems to confirm that as long as my water temp is 10*C (50*F) or greater then 10 mins is sufficient for a TOTAL KILL of S. cerevisiae and S. diastaticus as well as the six types of bacteria mentioned. A 6-7 log reduction (reasonable for sanitation over sterilization) probably happens even faster. This would correlate with my practical data from plating. Never see growth on multiple media after a 10 min cycle over 100ppm of PAA.

                              It would take longer or warmer temperatures for Candida mycoderma, Hansenula anomala, and Picha membranaefaciens for sure. not sure those are common in beer, but it could certainly happen.

                              I would say that concentration appears to be just as big of a factor for the total kill of the yeast organisms mentioned, but I would agree in saying temperature is much more of a factor in the killing of bacteria and spores.

                              Very good info.

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