An essential ingredient in winemaking.
Potassium Metabisulphite, (often referred to as "SO2", "sulfites" "meta", or "meta-bi") has several uses in winemaking. It is used at the crush, to help control the spoilage bacteria and indigenous yeast that may already be present on the fruit or the equipment. The amount used is enough to stop most of the unwanted organisms but not enough to hinder a cultured yeast, which has a higher tolerance to sulphites. This effectively "wipes the slate clean" for the cultured yeast to step in and rapidly colonize the must.
Sulphites also help to inhibit the enzymatic browning of musts and finished wines. During storage and in the bottle, sulphites at the proper levels will protect a wine by continuing to inhibit spoilage organisms, as well as by scavenging oxygen.
A convenient way to add sulphites is to use pre-measured Effervescent SO2 packets. The 2 gram size will add 9 ppm sulfites to a 60 gallon barrel or 18 ppm sulfites to a 30 gallon barrel. The 5 gram size will add 22 ppm to a 60 gallon barrel.
For more information refer to our MoreManuals! on Red or White Winemaking or one of the winemaking books that we offer for a complete explanation on how to properly manage sulphites.