S.A.I.N.S or Sulfite-free wines
Sulphur is used during the wine-making process for its antiseptic and antioxidant properties. It helps stabilize the wines. In high doses, sulphur may have adverse effects on our bodies, and tends to ’harden’ wine. In view of this, the best winemakers now use only a minimum amount of sulphur, so as to give the wine a certain degree of stability without detracting from its qualities. In the best wines, the doses of sulphur are generally sufficiently low for there to be no problem.
A few winemakers go still further and do not use any sulphur at all in the wine-making process. There are not many of these wines, but they have quite a reputation. Wines without added sulphur require absolutely perfect wine-making conditions, followed by the very best storage and preservation.
NB: As wine may contain sulphur from the grapes, the term "sulphur-free wine" is not fully accurate, unless understood as a simplification of "wine without added sulphur".
More information: Getting the most out of sulfite-free Natural wine.