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PRODUCT DETAILS
SULPHITES > Potassium Metabisulfite

Potassium metabisulfite, K2S2O5, also known as potassium pyrosulfite, is a white crystalline powder with a pungent sulfur odour. The main use for the chemical is as an antioxidant or chemical sterilant.

Density: 2.34 g/cm³, Melting point: 190 °C

Uses

It is used as a food additive, also known as E224.  It is restricted in use and may cause severe allergic reactions in sensitive persons.

Potassium is an inhibitor of the polyphenol oxidase enzyme.

Wine

Potassium metabisulfite is a common wine or must additive, in which it forms sulfur dioxide gas (SO2). This both prevents most wild microorganisms from growing, and it acts as a potent antioxidant, protecting both the color and delicate flavors of wine.

The typical dosage is 1/4 tsp (1.23 milliliters) potassium metabisulfite per six-gallon bucket of must (yielding roughly 75 ppm of SO2) prior to fermentation; then 1/2 tsp per six-gallon bucket (150 ppm of SO2) at bottling. Most commercial wineries do not add more than 30ppm at bottling.

Winemaking equipment is sanitized by spraying with a 1% SO2 (2 tsp potassium metabisulfite per L) solution.

Beer

Potassium metabisulfite is sometimes used in the brewing industry to inhibit the growth of wild yeasts, bacteria, and fungi. This is called 'stabilizing'. It is also used to neutralize chloramine that has been added to tap water at the source as a disinfectant. It is used both by homebrewers and commercial brewers alike. It is not used as much for brewing beer, because the wort is almost always boiled, which kills most microorganisms. It can also be added to strike water (the water used to mash the malted barley) in order to remove chloramines which can cause phenolic off flavors in beer.

Other uses
 

  •     Potassium metabisulfite is sometimes added to lemon juice as a preservative.
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  •     Potassium metabisulfite is used in the textile industry for dyeing and cotton printing.
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  •     Potassium metabisulfite is sometimes used to precipitate gold from solution in aqua regia (as an alternative to sodium sulfite).
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  •     It is a component of certain photographic developers and solutions used in photographic fixing.[5]
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  •     It is used as a bleaching agent in the production of Coconut cream
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  •     It is used in some pickles as a preservative