That’s my feeling, too.
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.
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.
The Star San wasn’t sprayed on before streaking.
The sanitizer was applied after ten minutes, not immediately.
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.
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.
It’s no secret. Lots of people use Star San/Saniclean for acid washing. It wouldn’t work if the yeast were killed.
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.
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.
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.
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.
Let me try to touch on a few things that have been brought up.
The plates are from White Labs online shop at yeastman.com - anyone can set up an account and order online. Be aware that some selective media plates have a very short shelf life. One product that I wish I bought in quantity is their sterile 50mL vials. They have a conical bottom, but also a ring to keep it upright. It’s a great vessel for the first step of growing up some yeast. I did have one contaminated agar plate from them. I’m hoping that it was a fluke and not a QC problem on their end. As an aside, I picked two colonies from the contaminated plate to step up and they are putting out some serious honey aroma. I know pentanedione is supposed to be a flaw, but right now is smells really nice to me. I’ll post more about my experience with WLP??? in the future.
As far as the experiment setup goes, I was not as concerned with the overall microbicidal activity of each sanitizer as I was in simply checking the effectiveness of each as a surface sanitizer for typical use in my home brewery. I am starting with equipment that I consider sufficiently clean of organic soils - everything cold side gets an extended soak and/or circulation with PBW and inspected for crud. I’m sure there are more accurate ways to test this out, but I still contend that my setup is a decent surrogate for this.
I am not claiming that the Star San is a superior disinfectant for treating heavily contaminated equipment. For those you need something broad spectrum (or just toss it if it’s easily replaceable). But I do think that it passes the “close enough for government work” sniff test for clean equipment that will be innoculated with an active and/or sizeable pitch of brewer’s yeast. I also think that an important part of sanitization that is easy to overlook is the “must remain wet for the entire required contact time” part of things. The foaming action of Star San is a big asset in this department. I suspect that once I flipped the agar plates to dry that some Star San clung to the plate for a while, essentially extending its contact time for a bit.
FYI - One of the reasons I chose tap water over an untreated plate as my control was to rule out a simple mechanical action of washing the contaminants off the surface as the primary mechanism of action. That certainly wasn’t the case here. That seems to strengthen the case that at least some antimicrobial activity is at work here.
Regardless of my results, if I were working with a slant of a culture that costs well beyond the total of all my other ingredients in a batch, I would certainly be using something as broad-spectrum as possible and ensuring it stayed wet for an extended contact time. Or just flamed anything possible.
Personally, my motivation for performing this experiment was that I felt myself falling into the trap of applying my medical knowledge of disinfectants to the brewery. But the goals are completely different - in medicine your goal is to reduce the count of pathogens to as close to zero as possible. In the brewery, we just need to reduce the amount of contaminants to a level where your pitch of yeast can rapidly outcompete them. Frankly, looking at the sparse dozen or so colonies on the iodophor plate, that’s probably well within the acceptable window.
One more random tangent I’ve thought of while mulling this all over - a solution containing both concentrated Iodophor and Star San diluted to the appropriate concentrations may pose the best of both worlds. The acidity of the Star San enhances the effect of iodophor, and the surfactant will keep it in place longer. Or I could just be half-asleep and rambling lol.
This is a great thread, thanks Eric for taking the time to do this and Mark for your extensive comments, I know you have been worried about burnout and I appreciate that you have remained active on this forum.
I have a few takeaways from all this. One comes from Mark’s contention that this experiment is not valid because Star San is “cheating” by remaining on the surface longer (cheating is my word, not Mark’s). Mark keeps alluding to the fact that the wort that is added to the fermenter will instantly wash it off and change the PH thusly making it ineffective. Fair enough but a fermenter is a very easy thing to clean thoroughly, I believe that washing and scrubbing with brewery cleansers that we all use (or soap and water for that matter) gets rid of enough of the microflora on its own to prevent infections and soaking in star san until wort is added keeps it that way. Since, as noted, Star San sticks to surfaces longer, its a good thing to have coating the surface of the fermenter wall above the wort level, keeping microbe growth in check until the krausen comes into contact with it before falling back into the beer. Also, wort that comes into contact with these surfaces should be getting a healthy pitch of the desired culture to overwhelm the small amount of microbes that survived, albeit in a weakened state.
I think the bigger problem is brewing equipment that is hard to wash: racking canes, tubing, spigots, bottling wands, air locks, kegging equipment etc. Its one reason I pour instead of rack my wort into the fermenter. These I currently soak in oxyclean and physically scrub what I can reach then soak in star san until use. This seems to do a good enough job based on no infections since using this method but they simply cannot be scrubbed thoroughly and should be replaced periodically. I wish I could soak them in alcohol but the volume needed is prohibitive. I do soak these in a bleach solution periodically and am considering quat tablets.
All of my tubing and brewing plasticware used to live in a bleach solution that was refreshed on a regular basis when I was still a single man. I used one of those big blue tubs that have rope handles. My wife was not crazy about that setup, so it went when she moved in.
The move away from glass to plastic fermentation vessels makes sanitizer choice much harder. Glass is easy to clean and sanitize. Plastic is more difficult to clean without damaging the surface, and it is porous (which is why my plasticware used to live a bleach solution. The beauty of stainless steel is that it can be steam sanitized.
The most abrasive thing I use to clean my plastic fermenters is a terry cloth towel and they all have remained free of (visible) scratches. I have dozens of glass carboys I use mostly for secondary and aging of mead. A cleaning solution and bottle brush works but I sure do wish I could get my arms in there.
The initial results are intriguing for sure - hopeful, even. However, I do think that more tests using different methodology are needed to give a better representation of sanitizer effects. My gut reaction is that StarSan works and Mark is wrong :P, but that conclusion is too simple to jump to and I’ve been burnt by “intuition” too many times.
Sooooo… What if a 5 ml of highly contaminated culture slurry (blend of sour dregs for instance) were added to 1000 ml of the various sanitizers (B151, iodophor, starsan, bleach water, etc) and then allowed to soak for the stated time, AND THEN streaked onto sterile plates. Would the resulting growth colonies then be representative of what’s making it’s way into our beer? IME, this gives the sanitizer the best possible chance of success based on manufacturers instructions.
In addition, it would seem necessary that one should streak a plate with a batch of wort just after chilling while still in the BK. This would also give insight into the microbe load that comes with our wort after having only been boiled and being exposed to the environment during the chilling phase. After all, this microbe load is something that most homebrewers experience unless chilling under a hood or covered (both of which could be individually evaluated on plates as well).
Once again, we’re at a dichotomy of science vs. results. I began homebrewing using BTF Iodophor and used it excliusively for 6-8 years. After developing what I think was a persistent low level infection, I switched to StarSan and it went away. I’ve used it now for at least 10 years and hundreds of batches and have not experienced an infection. To me, that’s pretty good proof. However, after reading Mark’s info about Iodophor, coupled with the fact that I work with the company that makes BTF Iodophor, has made me want to give it a second look. I have a new bottle that I’ll start using and compare the results. So, while you guys are debating experiment protocol and the finer points of chemistry, I’ll be brewing delicious beer and find out for myself. Frankly, what I expect is that I’ll see no difference and conclude that both are fine sanitizers.
All of the sanitizers used in brewing are effective against bacteria to some extent. The ability to kill yeast and mold are the areas that differentiate sanitizing agents for the most part. A more representative microbe source would be wort that is left to stand out in a home for a twelve hours before being covered and incubated. Most houses contain non-brewing yeast genera as well as mold spores to some extent.
The page linked below does a good job of explaining various sanitizing agents, including their modes of action and their weaknesses. With respect to acid-anionic sanitizers (the class to which Star San belong), a common theme is limited yeast and mold activity. The fact that people are acid washing yeast cultures with Star San goes a long way towards proving my point as well as the point made by the author of the linked web page and several other publications that claim the same thing.
^^ Agree 100%, Denny. I used iodophor for years before the switch to Star San - which means I should’ve brewed infected beer occasionally or even semi-regularly after the switch. Not so.
+2 I don’t doubt the facts Mark is referencing at all, I just think Star San is plenty good enough on well cleaned equipment as evidenced by low levels of infection or no infections on hundreds of batches by many homebrewers on this forum alone.
I wonder how different things would be if no sanitizing was done at all, but general cleaning was done very thoroughly. I wonder too how a final rinse (again, no sanitizing) with boiled and/or autoclaved water would differ from a final rinse with sanitizer that was mixed with “unsanitary” RO or tap water.
For many years I used a gravity transfer on the cold side. I had no way to recirculate hot wort through the plate chiller. To be on the safe side, I would always boil the chiller and cold side tubing (including the O2 tubing and stone) first thing brew day. I’d usually dip all of this in starsan right before use, thinking that I’d be taking care of anything that settled on the equipment (or came from my hands) while I was assembling things after removal from the small boil pot I used for the equipment. Sometimes the stuff was still hot when I needed it, and the starsan was a way to cool it down for easier handling. Perhaps the starsan dip was not needed and perhaps counterproductive?