Hi Lum

I agree that what you are saying is technically correct but I think
you are mixing apples and oranges. The definition of "an aseptic level"
of molecular SO2, is the level which will kill (dead) all *anaerobic
bacilli* normally found in wine. Things which are *not* "anaerobic
bacilli" are dealt with by "other means". So - the SO2 tolerance of
these "other things" has no relationship to "aseptic levels".

Vinegar bacteria is easy. It is *not* anaerobic, so it is dealt with by
eliminating (severely limiting) the availability of atmospheric oxygen
in the wine. Even though SO2 is not the agent that eliminates the
bug, it helps by scavenging oxygen so it is not available for the bug
to use.

While yeasts can function anaerobicly, they are not "bacilli", so they
also fall outside the definition of "aseptic level of SO2". It is well
known that the commercial yeasts we use are virtually *all* able to
function at SO2 levels well above the levels we consider "aseptic"
in winemaking. For this reason we deal with them by "other means".
Namely, we eliminate all sugars so it has nothing to feed on (a dry
wine) - or - we control it chemically (Sorbate/Benzoate etc) - or -
we sterile filter - or - we can raise the alcohol level above the
alcohol toxicity point of the yeast in question.
HTMS

FWIW - the last I heard the "aseptic" level is now considered to
be 0.83 ppm. Something about one of the bugs which_does_ fall
within the definition was determined to have a slightly elevated
tolerance. Can't even remember where I read that.

Best regards,
Frederick


"Lum" > wrote in message
...
> Frederick, Joanne and All,
>
> There may be some confusion about molecular sulfur dioxide levels and
> the microbial stability of wine.
>
> When sulfur dioxide is added to wine, some sulfur dioxide combines with
> other materials in the wine and becomes bound or "fixed." The remaining
> sulfur dioxide is in the "free" form. The free sulfur dioxide exists in
> three different forms, the molecular form, the bisulfite form and the
doubly
> ionized sulfite form. In general, only the molecular sulfur dioxide is
> effective against wine microbes, and many winemakers try and maintain a
> level of 0.8 milligrams of _molecular_ SO2 per liter of wine. But, the
> fraction of free sulfur dioxide that exists in the molecular form is
> strongly dependent upon the pH of the wine. Consequently, winemakers are
> always interested in wine pH so they can tell how much of the SO2 exists
in
> the molecular form.
>
> Unfortunately, many wine microbes can tolerate much higher levels of SO2.
> Some yeast strains, such as Saccharomyces bailii, can maintain normal
> fermentation rates when more than 200 ppm of SO2 are present (see Rankine,
> Making Good Wine, page 286). Vinegar bacteria are not very sensitive to
> SO2. "Sulfur dioxide has almost no effect on the acetic acid bacteria
> growth in the regular concentrations of SO2 in wine" (from Margalit,
> Concepts in Wine Chemistry, page 327).
>
> So, the value of 0.8 milligrams of molecular SO2 per liter of wine is only
a
> generalization and maintaining this level of SO2 certainly does _not_
> guaranty microbial stability of any wine. In fact, the value of 0.8 mg/l
is
> really only applicable to some of the lactic bacteria and some native
> yeasts.
>
> Regards,
> lum
>
> "frederick ploegman" > wrote in message
> ...
> > Hi Rick
> >
> > Please see my comments to Mark (above in this thread). Further
> > comments interspersed.......
> >
> > "Rick Vanderwal" > wrote in message
> > ...
> > > by the sounds of it, you should do that before adding the yeast....
> > > I just started a batch and wasn't aware of the ph factor...
> >
> > Let me try to explain some aspects of acid management. TA is
> > merely an empirically established *guideline*. Very helpful but
> > certainly not critical to success. OTOH - pH *is* critical to
> > success because it determines if the wine will have microbial
> > stability. This is why Joanne has stressed the importance of pH
> > in the other thread. While a pH meter is certainly the preferred
> > way to check pH, the papers you have are perfectly adequate for
> > doing this if you don't want to spend the money for a meter (they
> > ain't cheap).
> >
> > > and now my acid is a bit too high...
> >
> > See my comments to Mark on acid reduction.
> >
> > > so now I have to wait and perhaps cold stabilize after fermentation is
> > > all done...
> >
> > As Ben mentioned in the other thread, you will receive no benefit
> > by cold stabilizing this wine. "Tartaric" wines *must* be cold
> stabilized.
> > "Non-tartaric" wines (which your wine is) cannot form bitartrate
> > crystals because there is no tartaric acid present to combine with
> > the potassium. The reason that wines are categorized as "tartaric"
> > or "non-tartaric" is because acid management is radically different
> > for these two types. The above is just one aspect of this.
> > HTMS
> >
> > > or later add potassium or calcium carbonate...
> > >
> > > I would do it before adding the sugar....
> > > before fermentation...
> > > Rick
> > >
> > >
> > >
> > > "MkFn" > wrote in message
> > > om...
> > > > I'm about to start my first batch of raspberry wine and have
purchased
> > > > a Wine Acid Test Kit.
> > > >
> > > > When do I test the acid, before or after I add sugar?
> > > >
> > > > Are the guidelines for starting a must?
> > > > For example should I add sugar first, then test/adjust for acid
before
> > > > adding the yeast?
> > > >
> > > > Is there a specific order?
> > > >
> > > > thanks,
> > > > Mark
> > >
> > >
> >
> >
>
>
>