Typically white grapes are sulfited at crushing to protect against browning due to oxidation as well as for protection against microbial infection. The type of fruit and the style of wine being produced will have an impact on sulfiting decisions.

Fruit that is in poor condition contains higher levels of aldehydes which bind to added SO₂.įruit that is in exemplary condition at crushing may not even need to be sulfited before fermentation. When fruit is rotten or moldy or is suspected of having high levels of microorganisms present, more SO₂ must be added (50-100%). The condition of the fruit when it is crushed is an important factor in the amount of necessary SO₂ additions. TEMPERATURE:Īs temperatures increase, less stable compounds that bind SO₂ release those bonds, which in turn, increases the level of free SO₂ in the solution. There is a very large difference in quantity of SO₂ needed between a pH of 3.0 and 4.0. A lower pH solution will require less sulfur dioxide in order to maintain the proper level of molecular SO₂. The pH of the solution that the sulfur dioxide is added to is a major determining factor in the quantity of sulfur dioxide needed to provide adequate protection from microbes and oxidation. The most important factors to consider are: The quantity of sulfur dioxide added depends on many factors. Molecular SO₂ levels should be maintained between 0.5 and 0.8 ppm for proper protection. It is the molecular SO₂ that gives protection from microbes. The remainder of the sulfur dioxide is called free SO₂ with a very small portion remaining as molecular SO₂. Sulfur dioxide is highly reactive and a large portion (roughly half) of the compound is bound up immediately after addition. Sulfur dioxide (SO₂) is added to both must and wine for protection from oxidation and microbial spoilage.

Free so2 ph chart tor wine