Questioning Starsan

[danath34]

someone enlighten me... after reading about people using live yeast collected in their blow off container filled with a starsan solution, how can starsan really be effective as a sanitizer? I'm sure it's great for killing unwanted bacteria, but if you can salvage live yeast from a starsan solution, clearly it isn't effective for killing unwanted wild yeast.

can anyone share some insight? am I wrong?

 

[Newsman]

You don't use StarSan in your blowoff container if you want to harvest yeast.

 

[danath34]

Yeah, I assume most people intending to harvest their yeast will not put the blowoff in sanitizer. However, here are examples of starsan not killing yeast:

Using Starsan to wash yeast.
Post at the bottom by user3735 who made a successful starter from Starsan salvaged yeast.
Another successful starter from Starsan yeast.

 

[boscobeans]

Yeah, I assume most people intending to harvest their yeast will not put the blowoff in sanitizer. However, here are examples of starsan not killing yeast:

Using Starsan to wash yeast.
Post at the bottom by user3735 who made a successful starter from Starsan salvaged yeast.
Another successful starter from Starsan yeast.

From what I understand StarSan is a SURFACE sanitizer. It works in only a very specific range of acidity. When the properly mixed concentration of StarSan comes in contact with the baddies they die. In the cases you linked to the StarSan is being diluted almost instantly by having foaming wort bubbled into it, or having it mixed in a liquid starter. In one case a buffering agent is also used. I imagine that if you mix properly diluted StarSan in a liquid starter it will have some immediate effect and kill a good portion of the yeast, as one link shows, but once the acid level changes due to dilution it will begin to act, as many people claim, as a yeast nutrient and produce the yeast growth the link states.

On a surface such as a clean fermenter the properly diluted StarSan has direct and undiluted contact with the yeast or whatever and does its job. If the fermenter has a layer of water on it and a spray or two of StarSan is applied it will immediately become diluted.

StarSan is a surface acting product and it must come in direct and undiluted contact with the offending yeast or bacteria to have its full effect.

This is how I understand it, maybe someone who has a more recent education in biology can make it more clear. My last classes on bacteriology and epidemiology were back in 1968.

OMO

bosco

 

[danath34]

ok thanks for the info, bosco. So if I follow correctly, if a Starsan solution is dilluted by 50% it will no longer sanitize? That's what seems to have happened in the article about washing yeast with Starsan. He mixes 50/50 yeast slurry and starsan and lets it sit for an hour, then adds baking soda to neutralize the acid for flavor reasons in the final product. I guess I do not fully understand the chemistry of Starsan, because my intuition tells me that at half concentration, it would just take more contact time to sanitize.

For example with bleach, you can sanitize your drinking water in an emergency by adding 8 drops of bleach to a gallon of water.

So I guess the question is: why does Starsan not sanitize when dilluted even a relatively small amount compared to other sanitizers? Though I may be interested in doing an experiment to see if starsan does indeed kill yeast at all. It could be that it kills bacteria, but wild yeast infection is much less common, and other sanitation steps/precautions are simply keeping wild yeast out.

Just thinking out loud here.

 

[Newsman]

I think the issue with StarSan is that it's a weak acid, and diluting it reduces the strength of the acid even more, so it's no longer toxic to yeast.

 

[Psycotte]

Never question StarSan. Don't fear the foam.

 

[boscobeans]

I think the issue with StarSan is that it's a weak acid, and diluting it reduces the strength of the acid even more, so it's no longer toxic to yeast.

+1

Just like a lot of acids, tame when dilute and dangerous when undiluted.

5% to 8% acetic is great in salads but more concentrated solutions will burn the hide off of you.

Properly diluted StarSan along with dodecylbenzenesulfonate, which is an anionic detergent, act together to ruptiure cell walls of yeasts and bacteris.

Overly diluted and the acid is not strong enough to destroy the cell walls. I guess that just like the acetic acid when StarSan gets over diluted it makes a tasty treat for your yeast, and then acts like a yeast nutrient..

bosco

 

[LordUlrich]

It comes down to the way starsan kills infections. Starsan is an acid (with some other stuff like wetting agents). It kills by having a low pH. pH is highly dependent on concentration (pH is really a measurement of concentration of Hydrogen Ions vs Hydroxide Ions). As the pH drops to a point where it no longer will kill anything.

Things like bleach or iodphor are poisons and kill by a different mechanism (don't know exactly what that is). They can be diluted to a greater degree and still kill the bugs, but the contact time needed is longer.

As a side note healthy yeast is pretty resistant to acid when compared to bacteria. Yeast actually produce some acid in the fermentation process to kill off competing microbes. Starsan at appropriate concentrations should be enough to kill a healthy yeast cell, but a little dilution might make a big difference.
Also yeast washing is to kill off the weak cells, so you subject the yeast to a acid where the healthy can survive but the weak will die. It is hard on the healthy cells too but if they are truly healthy they will recover.

 

[grayhalladay]

In addition to what LordUlrich said acids and pH drops will dissolve and or penetrate bacterial cell walls and thus kill them. Yeasts are very different/ much more complex cells at a biochemical and physiological level, and are better equipped to resist changes in environment than simple bacteria, but, like if humans drank enough starsan, it would hurt at a certain concentration, though at a diluted level, it is possible they could survive.

If anything i said is wrong, please let me know. I have a basic knowledge of microbiology/ cell biology but I could always use more!

 

[danath34]

ok these explanations make sense... I suppose I CAN trust it lol. I've been using bleach for the peace of mind, but I'll give Starsan a try on the next brew.

Thanks for the info guys