Vintner Resources

Potassium Metabisulfite is a stable source of sulfites in winemaking. The use of sulfur compounds is not a recent innovation. The Dutch shipping companies popularized the use of sulfur in the 16th century by refusing to ship any wines not treated. They insisted on the use of sulfites because the treated wines were the only ones that survived a long sea voyage without spoiling.

Sulfites work by releasing free sulfur dioxide, which inhibits yeast, mold and bacteria. It does this in two ways: one, it kills some of the organisms outright, and two, it blocks the surviving organisms’ ability to reproduce. If your winemaking equipment is physically clean and you’ve rinsed it with a sulfite solution, nothing will grow on it for a short period of time.

To help prevent oxidation, sulfites are also added directly to wine after fermentation. Wine oxidation follows the same pattern that you see in the cut

Most winemakers use one or another of the available fining agents prior to filtering and think of fining only as a clarifying agent. While that is indeed the main purpose for fining any wine, fining actually can be done for several other reasons including colour, odour, flavour and stability.

WHAT IS IT?

Malolactic fermentation is the conversion by bacteria of malic acid into CO₂ and lactic acid.

One gram of malic acid converts roughly into 0.67 grams of lactic acid and 0.33 grams of CO₂.