Don’t fear the Starsan foam, a math explanation

DirtyPolock · 11-24-2010, 12:19 AM

So I don’t know if something like this exists somewhere else on the forum so my apologies if this is a duplicate. I want to try to explain why to not fear the foam via math.

Starsan has two active ingredients: Dodecylbenzenesulfonic acid (DDBSA) and Phosphoric acid (PA). Their concentration in straight starsan is 15% and 50% respectively. This means that for every mL of starsan there is 150 mg of DDBSA and 500 mg of PA.

If you mix up a 5 gallon batch of Starsan in your ale pail fermenter and use the recommended 30 mL of starsan then you have a total of 4.5 grams of DDBSA and 15 grams of PA per 5 gallons (18,927 mL) of water. This results in a concentration of 0.238 mg/mL of DDBSA and 0.793 mg/mL of PA in this mix.

At this point you will empty your ale pail before you add in your wort and yeast to make beer. After dumping your starsan batch you will have a little foam and diluted starsan left over. My guess is that you will have no more than 10 mL of this left in the fermenter and this is likely a stretch, but 10 mL makes for easy math. This means that there is 2.38 mg of DDBSA and 7.93 mg of PA left in your ale pail. At this point you will dilute it again with 5 gallons of your wort which will turn into beer. This results in the new concentration of 0.000126 mg/mL of DDBSA and 0.000419 mg/mL of PA.

Based on this concentration you will drink 0.0596 mg of DDBSA and 0.198 mg of PA in each pint of beer that you just fermented.

Well if I keg my beer and follow the exact same dilutions to sanitize my keg I would have double the amount that I just listed above (i.e. 0.1192 mg DDBSA/pint and 0.396 mg PA/pint). What does this mean in terms of toxicity? The lowest LD50 (dose where 50% of animals will die) for DDBSA that I could find was for a mouse which is 50 mg/kg. If I would need this same dose where I have a 50% chance of death I would need 5000 mg (5 grams) of DDBSA. This about 41,900 pints of beer that I draw from my keg.

The lowest reported lethal dose of PA for a human is 200mg/kg, which for me it would be 20000 mg (20 grams). For me this is around 50,500 pints of beer from my keg.

As there are only 40 pints in a 5 gallon keg so you can drink your entire keg before you get to the reported lethal doses of the starsan agents. You would die from fluid over load (low sodium) or acute alcohol toxicity if you would drink your entire keg in a sitting before you have problems with the left over starsan.

If you leave less than 10 ml of diluted starsan your fermenter or keg then you need to proportionally increase the numbers of beer that you need to drink to reach your limit. If you leave 5 mL in your fermenter then I would need to drink twice the number of beers that I listed above…2mL’s in my fermenter then 5 times the number of beers that I listed above, etc., etc., etc.

Well I hope that this helps to calm any fears regarding the left over starsan solution in your fermenters/bottles/kegs. Now I need to start working on drinking some beers and get close to my limit.

**Walker** · 11-24-2010, 02:04 AM

godamnit... i am WAY to ****ing drunk to read all of that, even though i REALLY want to read it.

**snccoulter** · 11-24-2010, 02:15 AM

Good to know. I always let the keg sit upside down for a while to get everything out. but there is always a bit of foam left..

WPStrassburg · 11-24-2010, 02:45 AM

HA, YOU'RE WRONG!!!!

I just finished #20 and I never started till 1 this aftgernoon. I'm still kiggin abd typion, si ur math is bugos/..........

ur, maybi it's the 10.2% RIS that's slurrrrrrin me speech??

So what part of the DDBSA and PA does the yeast consume as food? Does that increase the # of pints I can consume before i reach the PEL??

P.S. I like foam snake for some reason...., so faom is good!!

DirtyPolock · 11-24-2010, 02:50 AM

This math does not include any that is removed and consumed by the yeast as nutrition, or any that is neutralized by the change in the pH of the solution. This is really just a worst case scenario.

WPStrassburg · 11-24-2010, 02:59 AM

Quote:

Originally Posted by DirtyPolock

This math does not include any that is removed and consumed by the yeast as nutrition, or any that is neutralized by the change in the pH of the solution. This is really just a worst case scenario.

si, i kin keep drinkin????????/

ultravista · 11-25-2010, 07:47 PM

good stuff!

trigger · 11-27-2010, 02:09 AM

Ok, I love this. As Biochem I had already worked this out, wondering what would happen if I mixed up my starsan too strong and then drank some. It's great to see that someone else has done it too! On a side note, I agree that 10mL of liquid diluted sanitizer is a very high estimate, but like you said, worst case scenario.

P.S. I didn't bother checking your math, but I'm pretty sure I came up with something similar if you convert to volume of starsan drank at 2oz/5gal.

dobeluvr · 11-28-2010, 11:27 PM

So what if you left a quart in the fermenting bucket when you added the wort? Is the taste gonna be noticeable, or should the yeast process most of it?

DirtyPolock · 11-29-2010, 12:17 AM

Quote:

Originally Posted by dobeluvr

So what if you left a quart in the fermenting bucket when you added the wort? Is the taste gonna be noticeable, or should the yeast process most of it?

I'm sure that the yeast will process a lot if not all of the starsan. I don't know how much this occurs with the yeast but here are a few other posts where people did the same thing and they reported that the beer turned out fine.

Quote:

Originally Posted by FlyGuy

I have done my share of bonehead things, too.

1. When I started brewing I used to ferment my beer in plastic buckets in a cubby-hole behind the furnace in my basement. It worked well to begin with (summer), and then I couldn't figure out why suddenly all my beer started tasting awful (winter when furnace was cycling in and out).

2. Racked my wort into the carboy before I had drained 2 - 3 quarts of Star San (beer turned out fine).

Quote:

Originally Posted by discgolfin

I have done many small minor mistakes..nothing too major.

One bone headed thing was adding beer to secondary with about 1/2 gallon of star san in it..turned out fine.

These are in the secondary when there is not even as much yeast as the primary so if you do it in the primary then I'm betting its just as safe.