Sulphur dioxide is used by wineries to inhibit oxidation and prevent the enzymatic action which causes browning of white grape juice. But some wineries, such as Simi of California, chose not to add sulphur dioxide to white grape juice prior to fermentation.
To control the browning action, Simi precipitates out a certain group of juice phenols that react with the oxygen and cause browning.
The second reason SO2 is added to juice is to wipe out natural bacteria and wild yeasts clinging to the grapes in order to have a controlled fermentation. The alternative used by Simi to control SO2’s antimicrobial action in juice is to chill the grapes.
Chilling white grapes succeeds by allowing the winemaker to perform cold skin contact to extract flavor compounds from the skins without also extracting bitter compounds.
Since chilling doesn’t kill germs as does SO2, the process depends on receiving healthy grapes from the vineyard.
So it is possible for a large scale winery to limit the use of sulphur and not give in to liberal doses to make production easier.
Bravo to wineries like Simi!