Can commercial yeast finish AF through a KMBS addition ?

[chonn]

Let's say I have red wine must at 0.995 SG....AF is basically done and the wine is "dry" but there is probably still some sugar there.

Let's also say that I press that 0.995 SG wine off the skins and immediately add 40ppm KMBS and add 0.06 ph points of acid.

How much of my KMBS did I just waste killing my own yeast that was probably still alive?

What did my KMBS addition do to the ability of that yeast to finish up the remaining points of SG and finish up any residual sugar?

Thanks.

 

[winemaker81]

Commercial yeast is typically K-meta tolerant, well above that of wild yeast and bacteria. I've added 100 ppm to a wine that developed H2S and the ferment didn't even slow down.

 

[chonn]

Commercial yeast is typically K-meta tolerant, well above that of wild yeast and bacteria. I've added 100 ppm to a wine that developed H2S and the ferment didn't even slow down.

Curious--did you add that 100ppm to *must* or was this fermentation going on after you pressed off the skins?

The other part of my question is something I am still wondering about--even though the AF continues and the commercial yeast keeps doing its job, why isn't the sulfur all bound up in the yeast and "wasted" because it attached to things that weren't bad?

I am thinking of so2 as something that gets "spent" on whatever it can bind itself to and it seems like a rocking fermentation would "waste" the free so2 on all the yeast floating around.

 

[winemaker81]

Curious--did you add that 100ppm to *must* or was this fermentation going on after you pressed off the skins?

To the must. It was two days into fermentation when I smelled H2S.

H2S is one of the few things in winemaking where a quick response is necessary. The longer ya wait, the worse it gets.

EDIT: I only answered the first question.

The other part of my question is something I am still wondering about--even though the AF continues and the commercial yeast keeps doing its job, why isn't the sulfur all bound up in the yeast and "wasted" because it attached to things that weren't bad?

I never actually considered this. However, SO2 can "poison" yeast that are not immune to it, but won't chemically bind because they are living creatures. Alcohol, CO2, and other constituents in wine are not chemically attracted to SO2, so it has no effect upon them. OTOH, ions like O2 ARE chemically attracted to SO2 (due to ionization?), so they bind.

That's an off-the-cuff idea. Someone with up-to-date knowledge of the chemistry involved can provide a more accurate explanation. Chem 101 is a LONG time in my rear view mirror.

 

[chonn]

Oh....so you're saying the free so2 is doing two unrelated things: killing some critters but not binding to them (and remaining as free so2 I guess?) and then also binding to oxygen when it is present and becoming non-free so2....

So my commercial yeast are just swimming around in a slightly more sulfurous pool but if there is no oxygen around that free so2 will remain free?

 

[winemaker81]

Oh....so you're saying the free so2 is doing two unrelated things: killing some critters but not binding to them (and remaining as free so2 I guess?) and then also binding to oxygen when it is present and becoming non-free so2....

So my commercial yeast are just swimming around in a slightly more sulfurous pool but if there is no oxygen around that free so2 will remain free?

That's more-or-less correct.