Starsan Kill Curve

[kjball]

So, I had my class do my dirty work. But we all will reap the benefits.

I had the micro class test Starsan as an antiseptic. The sample I used had been in the carboy for about 1 month, pH was 1.6.

The gist of it is that at 100% the recommended dosage (label instructions), Starsan kills everything after 2.5 minutes (first data point) No shocker here, right?

at 50% Concentration, all Gram Positive bacteria were killed after 2.5 Minutes (again, first data point). There were some Gram negative bacteria present after 2.5 minutes, but none at 5 min.

At 10% Concentration, there was no measurable effect on Gram negative, and some affect on Gram Positive.

The Concentration I speak of is the label instructed dilution assumed to be 100%. I have some pictures I can share, but they will take some deciphering.

Anyway, I hope this is somewhat informative. There's nothing shocking here, but to me it proves that Starsan, after 1 month, is still a very effective sanitizer, bordering on antiseptic.
I'll do Iodophor next semester.

[DrPaulsen]

That's fascinating -- thanks for the data!  Did you guys look at the impact on brewer's yeast by Starsan?  The other claim the manufacturer makes is that it has relatively benign effects to brewer's yeast, despite being a good anti-microbial agent.


On Fri, Mar 29, 2013 at 12:36 PM, kjball <brew-tech@crbeernuts.org (brew-tech@crbeernuts.org)> wrote:

So, I had my class do my dirty work. But we all will reap the benefits.

I had the micro class test Starsan as an antiseptic. The sample I used had been in the carboy for about 1 month, pH was 1.6.

The gist of it is that at 100% the recommended dosage (label instructions), Starsan kills everything after 2.5 minutes (first data point) No shocker here, right?

at 50% Concentration, all Gram Positive bacteria were killed after 2.5 Minutes (again, first data point). There were some Gram negative bacteria present after 2.5 minutes, but none at 5 min.

At 10% Concentration, there was no measurable effect on Gram negative, and some affect on Gram Positive.

The Concentration I speak of is the label instructed dilution assumed to be 100%. I have some pictures I can share, but they will take some deciphering.

Anyway, I hope this is somewhat informative. There's nothing shocking here, but to me it proves that Starsan, after 1 month, is still a very effective sanitizer, bordering on antiseptic.
I'll do Iodophor next semester.



Bad people drink bad beer. You don't usually see an empty bottle of Rochefort tossed onto the side of the road

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[kjball]

I did not. that's a curveball that the students aren't ready for.....Getting them to understand Gram classifications is hard enough. I can run a little independent experiment to check it. My expectation is that Yeast, along with other fungi would fall more towards the Gram neg side of things. This is an educated guess based on cell wall structure, Fungi lack an outer cell membrane, like Gram neg. However they have totally different cell wall composition. (Chitin vs peptidoglycan) I'm not sure what effect acid has on Chitin.

[DrPaulsen]

http://www.brewingscience.com/PDF/BSI_brewers_lab_handbook.pdf


Pg 3, par 1 (below "Simple Tests for Identifying Bacteria") - "All bacteria are divided into two categories: gram-positive (takes on crystal violet stain and turns blue) and gram-negative (takes on safranin stain and turns pink). Yeasts are gram-positive."



On Fri, Mar 29, 2013 at 1:29 PM, kjball <brew-tech@crbeernuts.org (brew-tech@crbeernuts.org)> wrote:

I did not. that's a curveball that the students aren't ready for.....Getting them to understand Gram classifications is hard enough. I can run a little independent experiment to check it. My expectation is that Yeast, along with other fungi would fall more towards the Gram neg side of things. This is an educated guess based on cell wall structure, Fungi lack an outer cell membrane, like Gram neg. However they have totally different cell wall composition. (Chitin vs peptidoglycan) I'm not sure what effect acid has on Chitin.



Bad people drink bad beer. You don't usually see an empty bottle of Rochefort tossed onto the side of the road

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[kjball]

yeah, I'm all screwed up there, gran neg have the outer cell wall, that's why they're negative. Yeast would be more like gram pos, as stated in the book. The problem with that statement is that even though they take on stain, the composition is different. It's Friday and I need a beer.

[Derek]

I don't think StarSan is supposed to be benign to yeast, except that you do not need to rinse any residual amounts from the fermentation vessel ("don't fear the foam"). In five gallons of wort any residual StarSan will break down into simple phosphates (which will add very slightly to hardness and act slightly as a yeast nutrient).

At recommended concentrations, StarSan should be a stone cold killer to yeast.

[daryl]

Thank you for this helpful post.

I have just restarted my brewing efforts and I am just now using Starsan vs. Bleach; and it is a huge time saver and worth every penny. I mixed up a batch when I brewed in Dec; but most of that went down the drain, but not until I had sanitized all of my equipment that had been standing in my basement for the better part of 15 years!

When I bottled earlier this month I did not mix as much and, what was leftover, I filled my two spray bottles and three Champagne bottles for use later - they are stored in a dark cool place, next to my beer. I recall reading that mixed Starsan has a relatively long shelf life if it is not exposed to air. I've also read elsewhere in this forum, that mixed Starsan is good to use if it is not cloudy.

It is probably a moot point as I do not expect that my three bottle supply will be around longer than a month or two if I brew at least once a month.

With regard to the Starsan effect on yeasts, I think your results provide an indication of that effect - "At 10% Concentration, there was no measurable effect on Gram negative, and some affect on Gram Positive.". When I spray my little Heineken bottles and fill them while still wet, the resulting Starsan concentration has to be much less than 1% and therefore have little effect on the live yeasts required to carbonate the beer. If Yeast reacts similar to Gram Neg/Pos. Were you able to run additional tests?

Does anyone have an opinion/experience on the extended shelf life of mixed Starsan?

D

[Matt F]

I go by the if it is not cloudy use it rule for star san. I usually mix up 2.5 gallons and then store that in a 2.5 gallon keg when not in use. I have had batches last through multiple uses for up to 6 months. Key is to store so won't be exposed to much air. I have not had any issues following the cloudy rule. Really saves some coin when you can re-use it multiple times. You also don't need to soak everything. Spraying on surfaces seems to do the trick. I had a big bottle of star san last me over three years with a lot of brews over that time before I ran out.

[whitedj]

Also... use soft water. A friend has hard water and it turns cloudy fast, although never had a problem. True test is pH.

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[bf514921]

i second the ph, I have litmus paper for that, if its above 3 I believe, its toast, cloudy or not.

[Steven P]

I third the PH test. City water in CR makes my star san cloudy overnight. I test with a PH strip prior to use.

Also, a real money saver is to use a syringe to mix to the recommended dosage without making up a 5 gal batch. 7 ml (1/4 oz) star san per gallon jug of water is my go to mix method.

A 32 oz bottle will last a damn long time using 7 ml at a time.