Sulfites in wine

[Thomas]

Edit button? The last time I tried using it nothing happened; I must have waited a millUion hours.

Pergamum: free and bound, hmmm. It is something like this, and maybe Dick Peterson will get into the fray.

When you add SO2 to wine some of it is gobbled into solution and some stays "free" or suspended. The free stuff can be inhaled; ever notice a match-like burst emanating from a glass of young wine? That would likely be free SO2. The free stuff also protects against oxidation.

As the free SO2 dissipates over time, each addition of SO2 to make up for loss along the winemaking route also adds more binding SO2.

SO2 is measured, then, two ways: free and bound. The 350 ppm you referred to is likely the limit for bound SO2. If free were ever that high the wine would suffer from a powerful odor and more asthmatics would be exposed. Most wines fall into the range from 20 to 40 ppm free SO2, usually more than enough to keep oxygen at bay.

Additions of SO2 depend upon the wine's ph and handling. A low ph helps to require less additions of SO2 (high protective acidity makes that possible) too much handling of course exposes wine to oxygen and thereby requires careful SO2 monitoring.

Hope this helps. I know I have skimmed and by-passed a lot.