First of all, in order to avoid any confusion I would like to briefly clarify the difference between sulphur applied in the vineyard and sulphur used in the winery.
The first is applied as an anticryptogamic (fungicide) element to fight powdery mildew in particular, and exists either in a spray form (powdered sulphur), or in an even finer, micronised form (sulphur soluble in a liquid spray). This sulphur adheres to the leaves of the vine for a few days, and, during the process of sublimation (transformation from a solid to a gaseous phase), it releases vapours that interfere with the metabolism of the fungus.
The second is used to stabilise wines. In this case, the term sulphites is employed. This is obtained by burning elemental sulphur which releases the gas sulphur dioxide (SO2), and is similar to the burning of carbon molecules which release carbon dioxide (CO2). As it is quite irritant and impractical to use directly, it is generally dissolved in water to obtain sulphites (H2SO3). It is this watery solution that the winemaker can add to the wine during vinification and bottling. It is of course only the second use that I will discuss here.
What are the properties that make sulphur dioxide so indispensable? It is a remarkable preservative that protects the wine against two major risks which threaten the wine over the course of its life: microbiological contamination and oxidation. Thus, SO2 is both an antiseptic (antibacterial and antifungal depending on the dose) and an antioxidant.
Yet, used in large doses, it leads to serious problems:
In biodynamics, vinification standards seek to prevent the excessive use of additives, sulphites in particular, which could reduce the original energies present in the grapes. The objective is to administer a dose which corresponds to the actual need of the wine. This is truly the work of an artisan, determined on a case by case basis: wine by wine, vintage by vintage. For this reason, it is absolutely impossible to formulate a general rule for all, and standards simply set a maximum limit which is more restrictive than the law. Yet, you will find substantial differences in the quantities of added sulphites. If you compare two biodynamic producers, some even succeed in regularly doing without it altogether. The following list is an indication of total sulphur dioxide limits according to various 2011 standards. I have taken the example of a white Burgundy: a dry, white wine with long barrel maturation.
The Association des Vins Naturels is a body of producers and